Synthesis, antimicrobial, and anti-inflammatory activities of novel 5-(1-adamantyl)-4-arylideneamino-3-mercapto-1,2,4-triazoles and related derivatives.

The reaction of 5-(1-adamantyl)-4-amino-3-mercapto-1,2,4-triazole (5) with various aromatic aldehydes in ethanol or acetic acid yielded the corresponding 4-arylideneamino derivatives 6a-v. Treatment of the 4-(2,6-difluoro- and dichlorobenzylideneamino) derivatives 6o and 6q with 1-substituted piperazines, and formaldehyde solution in ethanol afforded good yields of the corresponding 5-(1-adamantyl)-4-(2,6-dihalobenzylideneamino-2-(4-substituted-1-piperazinylmethyl)-1,2,4-triazoline-3-thiones 7a-p. 5-(1-Adamantyl)-4-arylideneamino-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thiones 8a-n, were similarly prepared via the reaction of the corresponding arylideneamino derivative with ethyl 4-piperidinecarboxylate and formaldehyde solution in ethanol. Compounds 6a-v, 7a-p and 8a-n were tested for in vitro activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Several derivatives showed good or moderate activities, particularly against the tested Gram-positive bacteria. In addition, the in vivo anti-inflammatory activity of 21 compounds was determined using the carrageenan-induced paw oedema method in rats. Compounds 7d, 7g, 7i, 7j, 7l, 8c, 8e and 8l showed good or moderate dose-dependent activity in this area.

1. Introduction

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most widely used therapeutics, primarily for the treatment of pain and inflammation in arthritis. The development of microbial resistance has necessitated the search for new potent antibacterial and antifungal agents. Derivatives of adamantane which have long been known for their antiviral activity against the influenza [1,2,3] and HIV viruses [4,5,6,7], were also associated with central nervous [8,9,10], antimicrobial [11,12,13,14,15] and anti-inflammatory activities [14,15,16,17,18]. 1,2,4-Triazole derivatives were reported to possess diverse biological activities, such as antibacterial [19,20,21] and anti-inflammatory [22,23,24,25] properties. In addition, several 5-substituted-4-arylideneamino-3-mercapto-1,2,4-triazoles and their piperazinomethyl derivatives were reported to exhibit significant antimicrobial activity [26,27,28]. In continuation to our interest in the chemical and pharmacological properties of adamantane derivatives [6,11,14,15,16], we report herein the synthesis, antimicrobial and anti-inflammatory activities of a new series of 5-(1-adamantyl)-4-arylideneamino-3-mercapto-1,2,4-triazoles and their piperazinomethyl and piperidinomethyl Mannich bases.

2. Results and Discussion

2.1. Chemistry

5-(1-Adamantyl)-4-amino-3-mercapto-1,2,4-triazole (5) was prepared starting from adamantane-1-carboxylic acid (1) via esterification with methanol to yield the methyl ester 2, which was subsequently reacted with hydrazine to yield adamantane-1-carboxylic acid hydrazide (3). Treatment of 3 with carbon disulphide in ethanolic potassium hydroxide yielded the corresponding potassium N'-(1-adamantylcarbonyl)dithiocarbazate (4), which was cyclized by heating with hydrazine to yield 5-(1-adamantyl)-4-amino-3-mercapto-1,2,4-triazole (5) in good overall yield [29]. Treatment of compound 5 with the appropriate aromatic aldehydes under reflux in ethanol for 5 h yielded the corresponding arylideneamino derivatives 6a-v in reasonable yields. In the cases of the reactions with 2-nitro-, 4-nitro-, 2,4-dichloro-, 3,4-dichloro-, 2,4-dinitro-, or 4,5-dimethoxy-2-nitrobenzaldehyde, the yields were very poor. This may be attributed to the poor solubility of these aldehydes in ethanol. However, carrying out the reaction in acetic acid, in which these aldehydes are freely soluble, in addition to its higher boiling point, greatly increased the yield (Scheme 1, Table 1).

Scheme 1

Synthetic Pathway for Compounds 6a–v.

Table 1

Melting points, crystallization solvents, yields, molecular formulae and molecular weights of compounds 6a–v.

Comp. No.	R	Mp (ºC)	Cryst. Solv.	Yield (%)	Molecular Formula (Mol. Wt.)
6a	H	222-224	EtOH/H2O	81	C19H22N4S (338.47)
6b	2-F	226-228	EtOH	74	C19H21FN4S (356.46)
6c	4-F	255-257	EtOH	71	C19H21FN4S (356.46)
6d	2-Cl	223-225	EtOH	75	C19H21ClN4S (372.91)
6e	4-Cl	207-209	AcOH	68	C19H21ClN4S (372.91)
6f	4-Br	228-230	EtOH/H2O	59	C19H21BrN4S (417.37)
6g	2-OH	238-240	EtOH	79	C19H22N4OS (354.47)
6h	4-OH	264-266	EtOH	82	C19H22N4OS (354.47)
6i	4-CH3	208-210	EtOH/H2O	80	C20H24N4S (352.50)
6j	2-OCH3	226-228	EtOH	77	C20H24N4OS (368.50)
6k	4-OCH3	214-216	EtOH	81	C20H24N4OS (368.50)
6l*	2-NO2	226-228	EtOH	52	C19H21N5O2S (383.47)
6m*	4-NO2	242-244	AcOH	50	C19H21N5O2S (383.47)
6n	4-(CH3)2N	223-225	EtOH	66	C21H27N5S (381.54)
6o	2,6-F2	241-243	EtOH	68	C19H20F2N4S (374.45)
6p	2-Cl,6-F	219-221	EtOH	62	C19H20ClFN4S (390.91)
6q	2,6-Cl2	207-209	DMF	49	C19H20Cl2N4S (407.36)
6r*	2,4-Cl2	233-235	AcOH	62	C19H20Cl2N4S (407.36)
6s*	3,4-Cl2	237-239	AcOH	69	C19H20Cl2N4S (407.36)
6t	3,4-(CH3O)2	191-193	EtOH	86	C21H26N4O2S (398.52)
6u*	2,4-(NO2)2	245-247	AcOH	49	C19H20N6O4S (428.46)
6v*	2-NO2,4,5-(CH3O)2	145-147	AcOH	68	C21H25N5O4S (443.52)

* Prepared by method B.

The 2,6-difluoro- and dichlorobenzylideneamino derivatives 6o and 6q were reacted with several 1-substituted piperazines and formaldehyde solution in ethanol to yield the corresponding N-Mannich bases 7a–p in good yields. The reaction was carried out by heating the reactants in ethanol for 15 min to enhance the solubility of compounds 6o and 6q. On monitoring the reaction with thin layer chromatography (TLC), the starting compounds 6o and 6q disappeared completely after 15 minutes and the products either precipitated on standing or after addition of water. The 5-(1-adamantyl)-4-arylideneamino-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione N-Mannich bases 8a–n were similarly prepared via the reaction of the corresponding 5-(1-adamantyl)-4-arylideneamino-3-mercapto-1,2,4-triazole with ethyl 4-piperidinecarboxylate and formaldehyde solution by heating the reactants in ethanol for 20 min (Scheme 2, Table 2 and Table 3). The structures of newly synthesized compounds 6a–v, 7a–p and 8a–n were confirmed by 1H-NMR, 13C-NMR and mass spectra.

Scheme 2

Synthetic Pathway for Compounds 7a–p and 8a–n.

Table 2

Melting points, crystallization solvents, yields, molecular formulae and molecular weights of compounds 7a–p.

Comp. No.	X	R	Mp (°C)	Cryst. Solv.	Yield (%)	Molecular Formula (Mol. Wt.)
7a	F	CH3	102-104	EtOH/H2O	54	C25H32F2N6S (486.62)
7b	F	C2H5	169-171	EtOH/H2O	89	C26H34F2N6S (500.65)
7c	F	COOC2H5	156-158	EtOH/H2O	82	C27H34F2N6O2S (544.66)
7d	F	C6H5	151-153	EtOH	79	C30H34F2N6S (548.69)
7e	F	4-FC6H4	140-142	EtOH/H2O	80	C30H33F3N6S (566.68)
7f	F	3-CF3C6H4	132-134	EtOH/H2O	88	C31H33F5N6S (616.69)
7g	F	2-CH3OC6H4	184-186	EtOH/CHCl3	85	C31H36F2N6OS (578.72)
7h	F	C6H5CH2	148-150	EtOH	80	C31H36F2N6S (562.72)
7i	Cl	CH3	109-111	EtOH/H2O	68	C25H32Cl2N6S (519.53)
7j	Cl	C2H5	117-119	EtOH/H2O	75	C26H34Cl2N6S (533.56)
7k	Cl	COOC2H5	136-138	EtOH/H2O	72	C27H34Cl2N6O2S (577.57)
7l	Cl	C6H5	170-172	EtOH	83	C30H34Cl2N6S (581.60)
7m	Cl	4-FC6H4	184-186	EtOH	85	C30H33Cl2FN6S (599.59)
7n	Cl	3-CF3C6H4	159-161	EtOH	86	C31H33Cl2F3N6S (649.60)
7o	Cl	2-CH3OC6H4	139-141	EtOH	67	C31H36Cl2N6OS (611.63)
7p	Cl	C6H5CH2	178-180	EtOH	80	C31H36Cl2N6S (595.63)

Table 3

Melting points, crystallization solvents, yield percentages, molecular formulae and molecular weights of compounds 8a–n.

Comp. No.	R	Mp (°C)	Cryst. Solv.	Yield (%)	Molecular Formula (Mol. Wt.)
8a	H	125-127	EtOH/H2O	82	C28H37N5O2S (507.69)
8b	2-F	134-136	EtOH/H2O	72	C28H36FN5O2S (525.68)
8c	2-Cl	158-160	EtOH	75	C28H36ClN5O2S (542.14)
8d	4-CH3	135-137	EtOH/H2O	92	C29H39N5O2S (521.72)
8e	2-OH	127-129	EtOH/H2O	79	C28H37N5O3S (523.69)
8f	4-OH	195-197	EtOH/H2O	84	C28H37N5O3S (523.69)
8g	4-OCH3	124-126	EtOH/H2O	88	C29H39N5O3S (537.72)
8h	2,6-F2	148-150	EtOH/H2O	69	C28H35F2N5O2S (543.67)
8i	2-Cl,6-F	148-150	EtOH	74	C28H35ClFN5O2S (560.13)
8j	2,6-Cl2	151-153	EtOH	75	C28H35Cl2N5O2S (576.58)
8k	2,4-Cl2	129-131	EtOH	68	C28H35Cl2N5O2S (576.58)
8l	3,4-Cl2	186-188	EtOH	71	C28H35Cl2N5O2S (576.58)
8m	3,4-(CH3O)2	113-115	EtOH/H2O	76	C30H41N5O4S (567.74)
8n	2-NO2,4,5-(CH3O)2	182-184	EtOH/CHCl3	80	C30H40N6O6S (612.74)

2.2. Antimicrobial Testing

The newly synthesized compounds 6a–v, 7a–p and 8a–n were tested for their in vitro growth inhibitory activity against the standard strains of the Institute of Fermentation of Osaka (IFO) namely; Staphylococcus aureus IFO 3060, Bacillus subtilis IFO 3007, Micrococcus luteus IFO 3232 (Gram-positive bacteria), Escherichia coli IFO 3301, Pseudomonas aeuroginosa IFO 3448 (Gram-negative bacteria), and the yeast-like pathogenic fungus Candida albicans IFO 0583. The primary screening was carried out using the agar disc-diffusion method using Müller-Hinton agar medium [30]. The results of the preliminary antimicrobial testing of compounds 6a–v, 7a–p and 8a–n (200 μg/disc), the antibacterial antibiotic ampicillin trihydrate (100 μg/disc) and the antifungal drug clotrimazole (100 μg/disc) are shown in Table 4. The antimicrobial activity results of the 4-arylideneaminotriazoles 6a–v revealed that the aryl substituents greatly influenced the antimicrobial activity. The halo and hydroxyl derivatives were highly active particularly against the tested Gram-positive bacteria, while the nitro and methoxy derivatives were generally inactive. In addition, the hydroxy derivatives 6g and 6h showed marked activity against the tested Gram-negative bacteria. The 4-fluoro 6c and 4-bromo 6f derivatives were significantly active against Candida albicans. Based on the antibacterial activity of the arylideneamino derivatives 6a-v, and the previously reported high chemotherapeutic activity of several 2,6-dihalophenyl derivatives [31,32,33], the 2,6-difluoro- and dichlorobenzylideneamino derivatives 6o and 6q were selected to prepare their 4-substituted-1-piperazinyl Mannich bases 7a–p. The results of the antimicrobial activity of the 4-substituted-1-piperazinyl Mannich bases 7a–p were generally lower than those of the arylideneamino derivatives 6a–v but the specificity was almost similar. On the other hand, the antimicrobial activity of the 4-ethoxycarbonyl-1-piperidyl Mannich bases 8a–n was higher than the 4-substituted-1-piperazinyl Mannich bases 7a–p. The most potent member of these derivatives were the 4-hydroxybenzylidene 8f and the 3,4-dimethoxybenzylidene 8m derivatives which displayed strong broad spectrum activity. The minimal inhibitory concentration (MIC) for the most active compounds 6h, 6o, 7n, 8a, 8e, 8f and 8m against the same microorganism used in the primary screening was determined using the microdilution susceptibility method in Müller-Hinton Broth and Sabouraud Liquid Medium [34]. The MIC of the most active compounds, the antibacterial antibiotic ampicillin trihydrate and the antifungal drug clotrimazole (Table 5) were in accordance with the results obtained in the primary screening.

Table 4

Antimicrobial activity of compounds 6a–v, 7a–p and 8a–n (200 μg/8 mm disc), the broad spectrum antibacterial drugs gentamicin (100 μg/8 mm disc), ampicillin (100 μg/8 mm disc) and the antifungal drug clotrimazole (100 μg/8 mm disc) against Staphylococcus aureus IFO 3060 (SA), Bacillus subtilis IFO 3007 (BS), Micrococcus luteus IFO 3232 (ML), Escherichia coli IFO 3301 (EC), Pseudomonas aeuroginosa IFO 3448 (PA), and Candida albicans IFO 0583 (CA).

Comp. No.	Diameter of Growth Inhibition Zone (mm)*
	SA	BS	ML	EC	PA	C A
6a	10	13	-	-	-	-
6b	14	14	-	-	-	-
6c	16	17	-	-	-	17
6d	11	14	-	-	-	-
6e	14	16	-	-	-	-
6f	13	14	14	-	-	16
6g	14	16	12	15	13	-
6h	19	25	13	19	14	-
6i	15	18	15	-	-	-
6j	-	-	-	-	-	-
6k	-	-	-	-	-	-
6l	14	14	-	-	-	-
6m	-	-	-	-	-	-
6n	-	-	-	-	-	-
6o	18	19	-	-	-	-
6p	-	-	-	-	-	-
6q	14	16	-	-	-	-
6r	16	17	-	-	-	-
6s	17	17	-	-	-	12
6t	-	-	-	-	-	-
6u	-	-	-	-	-	-
6v	-	-	-	-	-	-
7a	13	15	-	-	-	-
7b	15	14	-	15	-	-
7c	11	15		-	-	-
7d	-	-	14	-	-	-
7e	-	-	-	-	12	-
7f	12	11	-	18	11	-
7g	-	-	-	-	-	-
7h	-	-	-	-	-	17
7i	12	11	-	-	-	-
7j	14	12	-	-	-	-
7k	-	11	-	-	-	-
7l	-	-	-	-	-	-
7m	13	12	-	-	-	-
7n	-	-	-	19	14	-
7o	-	-	-	-	-	-
7p	-	-	-	-	-	-
8a	12	19	16	-	-	-
8b	-	-	-	-	-	-
8c	-	-	-	15	-	-
8d	11	15	-	-	-	-
8e	17	22	-	-	-	13
8f	22	26	-	-	-	19
8g	15	11	-	-	-	-
8h	-	-	-	-	-	14
8i	14	15	-	-	-	-
8j	12	16	16	-	-	-
8k	15	17	-	-	-	-
8l	11	13	-	-	-	-
8m	20	24	17	19	16	-
8n	-	-	-	-	-	-
Gentamicin	26	25	18	20	19	NT
Ampicillin	23	21	19	17	16	NT
Clotrimazole	NT	NT	NT	NT	NT	21

* (-): Inactive (inhibition zone <10 mm). (NT): Not tested.

Table 5

The minimal inhibitory concentrations (MIC, μg/mL) of compounds 6h, 6o, 7n, 8a, 8e, 8f, 8m, the broad spectrum antibacterial drugs gentamicin, ampicillin and the antifungal drug clotrimazole against Staphylococcus aureus IFO 3060 (SA), Bacillus subtilis IFO 3007 (BS), Micrococcus luteus IFO 3232 (ML), Escherichia coli IFO 3301(EC), Pseudomonas aeuroginosa IFO 3448 (PA), and Candida albicans IFO 0583 (CA).

Comp. No.	Minimal Inhibitory Concentration (MIC, g/mL)*
	SA	BS	ML	EC	PA	C A
6h	2	1	ND	2	ND	ND
6o	ND	4	ND	ND	ND	ND
7n	ND	ND	ND	2	ND	ND
8a	ND	4	ND	ND	ND	ND
8e	ND	2	ND	ND	ND	ND
8f	2	1	ND	ND	ND	8
8m	2	1	ND	2	ND	ND
Gentamicin	2	2	2	0.5	1	ND
Ampicillin	2	0.5	2	2	2	ND
Clotrimazole	ND	ND	ND	ND	ND	2

* ND: Not determined.

2.3. Acute anti-inflammatory activity testing

The acute in vivo anti-inflammatory activity of 21 representative compounds (6b, 6e, 6h, 6j, 6r, 6t, 7b, 7d, 7g, 7j, 7l, 7m, 7p, 8a, 8c, 8e, 8f, 8h, 8k, 8l and 8n) was determined following the carrageenan-induced paw oedema method in rats [35]. The selection of the representative compounds and dose levels were made after carrying out pilot experiments which showed the absence of anti-inflammatory activity for some compounds and that the dose levels 20 and 40 mg/kg showed no signs of acute toxicity. The results of the anti-inflammatory activity of the tested compounds (20 & 40 mg/kg) and the potent anti-inflammatory drug Indomethacin (5 mg/kg) are listed in Table 6. The majority of the tested compounds showed varying degrees of activity. The highest activity was shown by compound 7l, which produced strong dose-dependent inhibition of carrageenan-induced paw oedema (>50%), while compounds 7d and 8c were moderately active (30–50%) at 20 & 40 mg/kg dose level. Compounds 7g, 7j, 8e, and 8l were moderately active at 40 mg/kg dose level and weakly active at 20 mg/kg level. The structure-anti-inflammatory activity of the tested derivatives revealed that the triazole N-2 and N-4 substituents greatly influence the anti-inflammatory activity.

Table 6

Anti-inflammatory effect of intraperitoneal injection of (20 & 40 mg/kg) of compounds 6b, 6e, 6h, 6j, 6r, 6t, 7b, 7d, 7g, 7j, 7l, 7m, 7p, 8a, 8c, 8e, 8f, 8h, 8k, 8l, 8n and Indomethacin (5 mg/kg) against carrageenan-induced paw oedema in rats.

Comp. No.	Mean % Reduction of paw oedema from controla
	20 mg/kg	40 mg/kg
Controlb	0 (± 0.04)
6b	-5.50 (± 0.13)*	-2.71 (± 0.12)*
6e	3.16 (± 0.11)*	-8.56 (± 0.07)*
6h	13.28 (± 0.15)**	11.29 (± 0.14)**
6j	11.06 (± 0.13)**	13.91 (± 0.11)**
6r	10.32 (± 0.09)**	10.54 (± 0.11)**
6t	21.92 (± 0.08)**	19.37 (± 0.07)**
7b	17.88 (± 0.11)**	20.01 (± 0.09)**
7d	39.16 (± 0.09)**	39.88 (± 0.89)**
7g	25.88 (± 0.07)**	38.37 (± 0.07)**
7j	27.95 (± 0.12)**	34.76 (± 0.10)**
7l	28.86 (± 0.08)**	50.44 (± 0.06)**
7m	13.06 (± 0.08)**	22.90 (± 0.08)**
7p	2.05 (± 0.06)*	4.99 (± 0.08)*
8a	23.23 (± 0.02)**	15.27 (± 0.05)**
8c	33.02 (± 0.11)**	37.66 (± 0.14)**
8e	20.41 (± 0.07)**	31.20 (± 0.09)**
8f	-18.25 (± 0.13)	1.36 (± 0.04)
8h	-20.21 (± 0.11)	-9.80 (± 0.07)
8k	9.91 (± 0.133)*	6.81 (± 0.09)*
8l	10.45 (± 0.10)**	35.01 (± 0.12)**
8n	-13.75 (± 0.18)*	-11.61 (± 0.10)*
Indomethacin (5 mg/kg)	52.79 (± 0.04)

a Results are expressed as mean % inhibition ± S.E.M. (n = 5) and compared with student “t” test.

b The group was injected with 1 ml of 0.5% aqueous carboxymethyl cellulose solution.

* Inactive: Significantly different from Indomethacin at p < 0.05.

** Activity comparable to Indomethacin (significantly different from Indomethacin at p < 0.05.

The N-2 unsubstituted adamantyltriazoles 6b, 6e, 6h, 6j, 6r and 6t were weakly active or completely inactive, while the N-2 piperazinomethyl derivatives 7b, 7d, 7g, 7j, 7l, 7m and 7p were generally active. The activity was also found to be dependent on the nature of the 4-arylideneamino and the 4-piperazinyl substituents. The activity of the 2,6-dichlorobenzylidene derivatives were slightly higher than their 2,6-difluoro-benzylidene analogues. It could be also concluded that the phenyl substituents are better compared with the ethyl, 4-fluorophenyl, 2-methoxyphenyl and benzyl substituents. The replacement of the 4-substituted-1-piperazinyl moiety with a 4-carbethoxy-1-piperidyl moiety resulted in marked decrease in activity, only the chloro derivatives 8c and 8l and the 2-hydroxy derivative 8e exhibited moderate activity. There are in fact a high number of enzyme/receptors involved in the inflammatory process. Without specific tests it is quite difficult to hypothesize the mechanism of action of the tested compounds, they may exert their action via inhibition of the cyclooxygenase enzymes like other nonsteroidal anti-inflammatory agents. In addition, the recently reported activity of some adamantane derivatives as selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) [36,37] should be taken inconsideration. The 11β-hydroxysteroid dehydrogenase type 1 converts cortisone to the active glucocorticoid cortisol, which is responsible for various metabolic disorders including water retention, thus the inhibition of 11β-HSD1 would result in increasing the intracellular cortisone level.

3. Experimental

3.1. General

Melting points (ºC) were measured in open glass capillaries using a Branstead 9001 Electrothermal melting point apparatus and are uncorrected. NMR spectra were obtained on a Bruker AC 500 Ultra Shield NMR spectrometer (Fällanden, Switzerland) operating at 500.13 MHz for 1H and 125.76 MHz for 13C; the chemical shifts are expressed in δ (ppm) downfield from tetramethylsilane (TMS) as internal standard; coupling constants (J) are expressed in Hz. Electrospray ionization mass spectra (ESI-MS) were recorded on a Waters QuatroMicro triple quadrupole tandem mass spectrometer at 4.0 and 3.5 kV for positive and negative ions, respectively. Elemental analyses (C, H, N, S) were in full agreement with the proposed structures within ±0.4% of the theoretical values. Monitoring the reactions and checking the purity of the final products were carried out by thin layer chromatography (TLC) using silica gel precoated aluminum sheets (60 F254, Merck) and visualization with ultraviolet light (UV) at 365 and 254 nm. The bacterial strains and Candida albicans fungus were obtained from the Institute of Fermentation of Osaka (IFO), Osaka, Japan. The reference drugs ampicillin trihydrate (CAS 7177-48-2), clotrimazole (CAS 23593-75-1) and indomethacin (CAS 53-86-1) were obtained from Sigma-Aldrich Chemie GmbH, Taufkirchen, Germany. The Sprauge-Dawley rats were purchased from local animal house (Abu-Rawash, Giza, Egypt). The animal experiments for the determination of the anti-inflammatory activity were carried out in agreement with the pertinent legal and ethical standards of the international guidelines.

3.2. 5-(1-Adamantyl)-4-arylideneamino-3-mercapto-1,2,4-triazoles

Method A: A mixture of the appropriate aromatic aldehyde (2.0 mmol) and 5-(1-adamantyl)-4-amino-3-mercapto-1,2,4-triazole (5, 0.5 g, 2.0 mmol) in absolute ethanol (10 mL) was heated under reflux for 5 h. On cooling, the separated solid was filtered, washed with cold ethanol (5 mL), dried and crystallized (Table 1). Method B(compounds 6l, 6m, 6r, 6s, 6u and 6v): A mixture of the appropriate aromatic aldehyde (2.0 mmol) and 5-(1-adamantyl)-4-amino-3-mercapto-1,2,4-triazole (5, 0.5 g, 2 mmol) in acetic acid (8 mL) was heated under reflux for 4 h. On cooling, the separated solid was filtered, washed with cold ethanol (5 mL), dried and crystallized (Table 1).

5-(1-Adamantyl)-4-benzylideneamino-3-mercapto-1,2,4-triazole 6a: 1H-NMR (DMSO-d6): δ 1.69–1.73 (m, 6H, adamantane-H), 2.02 (s, 3H, adamantane-H), 2.07 (s, 6H, adamantane-H), 7.58–7.65 (m, 3H, Ar-H), 7.92 (d, 2H, Ar-H, J = 7.0 Hz), 9.71 (s, 1H, CH=N), 13.82 (s, 1H, SH). 13C-NMR: 27.72, 35.28, 36.47, 38.61 (adamantane-C), 128.94, 129.78, 132.67, 133.17 (Ar-C), 156.04, 162.50 (triazole C-5 & CH=N), 165.02 (triazole C-3). MS, m/z (Rel. Int.): 338 (M+, 51), 261 (12), 236 (26), 235 (100), 221 (14), 202 (17), 135 (15), 104 (12), 90 (11), 77 (6).

5-(1-Adamantyl)-4-(2-fluorobenzylideneamino)-3-mercapto-1,2,4-triazole 6b: 1H-NMR (DMSO-d6): δ 1.71 (s, 6H, adamantane-H), 2.02 (s, 3H, adamantane-H), 2.08 (s, 6H, adamantane-H), 7.40–7.45 (m, 2H, Ar-H), 7.67–7.71 (m, 1H, Ar-H), 8.04 (t, 1H, Ar-H, J = 7.0 Hz), 10.18 (s, 1H, CH=N), 13.85 (s, 1H, SH). 13C-NMR: 27.77, 35.36, 36.49, 38.37 (adamantane-C), 117.0, 120.45, 125.92, 127.86, 135.25, 156.88 (Ar-C), 156.20, 162.44 (triazole C-5 & CH=N), 163.18 (triazole C-3). MS, m/z (Rel. Int.): 356 (M+, 44), 339 (25), 297 (17), 266(24), 260 (20), 235 (100), 234 (60), 220 (31), 135 (25), 122 (26), 108 (29), 96 (10).

5-(1-Adamantyl)-4-(4-fluorobenzylideneamino)-3-mercapto-1,2,4-triazole 6c: 1H-NMR (DMSO-d6): δ 1.71 (s, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.07 (s, 6H, adamantane-H), 7.34 (d, 2H, Ar-H, J = 6.5 Hz), 7.94 (d, 2H, Ar-H, J = 6.5 Hz), 9.71 (s, 1H, CH=N), 13.81 (s, 1H, SH). 13C-NMR: 27.73, 35.28, 36.47, 38.63 (adamantane-C), 116.40, 129.28, 131.09, 163.95 (Ar-C), 156.02, 162.54 (triazole C-5 & CH=N), 165.37 (triazole C-3). MS, m/z (Rel. Int.): 356 (M+, 17), 235 (100), 234 (58), 220 (14), 135 (34), 122 (22), 121 (62), 107 (18), 95 (44).

5-(1-Adamantyl)-4-(2-chlorobenzylideneamino)-3-mercapto-1,2,4-triazole 6d: 1H-NMR (DMSO-d6): δ 1.73 (s, 6H, adamantane-H), 2.03 (s, 3H, adamantane-H), 2.09 (s, 6H, adamantane-H), 7.58–7.70 (m, 3H, Ar-H), 8.15 (d, 1H, Ar-H, J = 7.5 Hz), 10.48 (s, 1H, CH=N), 13.89 (s, 1H, SH). 13C-NMR: 27.76, 35.41, 36.51, 38.70 (adamantane-C), 127.77, 128.64, 130.40, 130.96, 134.46, 135.69 (Ar-C), 156.27, 158.73 (triazole C-5 & CH=N), 162.44 (triazole C-3). MS, m/z (Rel. Int.): 374 (M+ +2, 25), 372 (M+, 100), 337 (34), 261 (25), 249 (26), 235 (58), 234 (48), 221 (20), 140 (32), 135 (21), 125 (26), 110 (12).

5-(1-Adamantyl)-4-(4-chlorobenzylideneamino)-3-mercapto-1,2,4-triazole 6e: 1H-NMR (DMSO-d6): δ 1.70 (s, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.06 (s, 6H, adamantane-H), 7.66 (d, 2H, Ar-H, J = 6.5 Hz), 7.93 (d, 2H, Ar-H, J = 6.5 Hz), 9.76 (s, 1H, CH=N), 13.81 (s, 1H, SH). 13C-NMR: 27.73, 35.29, 36.46, 38.63 (adamantane-C), 129.98, 130.56, 131.56, 137.89 (Ar-C), 156.04, 162.53 (triazole C-5 & CH=N), 163.66 (triazole C-3). MS, m/z (Rel. Int.): 374 (M+ +2, 10), 373 (M+ +1, 40), 372 (M+, 23), 371 (100).

5-(1-Adamantyl)-4-(2-bromobenzylideneamino)-3-mercapto-1,2,4-triazole 6f: 1H-NMR (DMSO-d6): δ 1.71 (s, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.09 (s, 6H, adamantane-H), 7.99 (d, 2H, Ar-H, J = 8.5), 7.86 (d, 2H, Ar-H, J = 8.5 Hz), 9.75 (s, 1H, CH=N), 13.82 (s, 1H, SH). 13C-NMR: 27.80, 35.30, 36.53, 38.64 (adamantane-C), 126.89, 130.71, 131.89, 132.93 (Ar-C), 156.04, 162.51 (triazole C-5 & CH=N), 162.73 (triazole C-3). MS, m/z (Rel. Int.): 418 (M+ +2, 20), 417 (M+ +1, 100), 416 (M+, 20), 415 (100).

5-(1-Adamantyl)-4-(2-hydroxybenzylideneamino)-3-mercapto-1,2,4-triazole 6g: 1H-NMR (DMSO-d6): δ 1.69–1.73 (m, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.07 (s, 6H, adamantane-H), 6.97–7.02 (m, 2H, Ar-H), 7.42–7.46 (m, 1H, Ar-H), 7.90–7.92 (m, 1H, Ar-H), 9.91 (s, 1H, CH=N), 10.55 (s, 1H, OH), 13.46 (s, 1H, SH). 13C-NMR: 27.74, 35.29, 36.47, 38.61 (adamantane-C), 117.26, 118.95, 120.26, 127.24, 134.72, 158.97 (Ar-C), 156.01, 161.63 (triazole C-5 & CH=N), 162.49 (triazole C-3). MS, m/z (Rel. Int.): 355 (M+ +1, 7), 354 (M+, 28), 353 (100).

5-(1-Adamantyl)-4-(4-hydroxybenzylideneamino)-3-mercapto-1,2,4-triazole 6h: 1H-NMR (DMSO-d6): δ 1.67–1.71 (m, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.06 (s, 6H, adamantane-H), 6.94 (d, 2H, Ar-H, J = 8.5 Hz), 7.76 (d, 2H, Ar-H, J = 8.5 Hz), 9.36 (s, 1H, CH=N), 10.38 (s, 1H, OH), 13.70 (s, 1H, SH). 13C-NMR: 27.73, 35.21, 36.48, 38.57 (adamantane-C), 116.65, 123.51, 131.18, 162.51 (Ar-C), 155.91, 162.32 (triazole C-5 & CH=N), 165.79 (triazole C-3). MS, m/z (Rel. Int.): 355 (M+ +1, 6), 354 (M+, 26), 353 (100).

5-(1-Adamantyl)-4-(4-methylbenzylideneamino)-3-mercapto-1,2,4-triazole 6i: 1H-NMR (DMSO-d6): δ 1.69–1.73 (m, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.06 (s, 6H, adamantane-H), 2.40 (s, 3H, CH3), 7.39 (d, 2H, Ar-H, J = 7.5 Hz), 7.81 (d, 2H, Ar-H, J = 7.5 Hz), 9.61 (s, 1H, CH=N), 13.77 (s, 1H, SH). 13C-NMR: 21.72 (CH3), 27.73, 35.26, 36.47, 38.60 (adamantane-C), 128.96, 129.99, 130.37, 143.57 (Ar-C), 156.0, 162.51 (triazole C-5 & CH=N), 165.19 (triazole C-3). MS, m/z (Rel. Int.): 351 (M+ -1, 14), 234 (100), 233 (32).

5-(1-Adamantyl)-4-(2-methoxybenzylideneamino)-3-mercapto-1,2,4-triazole 6j: 1H-NMR (DMSO-d6): δ 1.67–1.74 (m, 6H, adamantane-H), 2.02 (s, 3H, adamantane-H), 2.07 (s, 6H, adamantane-H), 3.89 (s, 3H, OCH3), 7.13–7.23 (m, 2H, Ar-H), 7.60–7.63 (m, 1H, Ar-H), 8.01 (d, 1H, Ar-H, J = 8.0 Hz), 10.02 (s, 1H, CH=N), 13.76 (s, 1H, SH). 13C-NMR: 27.74, 35.30, 36.49, 38.60 (adamantane-C), 56.54 (OCH3), 112.99, 120.74, 121.59, 126.69, 134.97, 159.84 (Ar-C), 156.13 (triazole C-5), 159.81 (CH=N), 162.39 (triazole C-3). MS, m/z (Rel. Int.): 369 (M+ +1, 7), 368 (M+, 23), 367 (100).

5-(1-Adamantyl)-4-(4-methoxybenzylideneamino)-3-mercapto-1,2,4-triazole 6k: 1H-NMR (DMSO-d6): δ 1.67–1.73 (m, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.06 (s, 6H, adamantane-H), 3.86 (s, 3H, OCH3), 7.13 (d, 2H, Ar-H, J = 8.5 Hz), 7.87 (d, 2H, Ar-H, J = 8.5 Hz), 9.50 (s, 1H, CH=N), 13.79 (s, 1H, SH). 13C-NMR: 27.73, 35.24, 36.48, 38.59 (adamantane-C), 56.04 (OCH3), 115.32, 125.11, 130.91, 163.43 (Ar-C), 155.95, 162.50 (triazole C-5 & CH=N), 165.12 (triazole C-3). MS, m/z (Rel. Int.): 369 (M+ +1, 29), 368 (M+, 76), 353 (33), 259 (33), 249 (37), 236 (51), 235 (49), 234 (29), 135 (54), 133 (100), 108 (112).

5-(1-Adamantyl)-4-(2-nitrobenzylideneamino)-3-mercapto-1,2,4-triazole 6l: 1H-NMR (DMSO-d6): δ 1.72 (s, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.07 (s, 6H, adamantane-H), 7.85 (t, 1H, Ar-H, J = 7.5 Hz), 7.94 (t, 1H, Ar-H, J = 7.5 Hz), 8.17 (d, 2H, Ar-H, J = 8.0 Hz), 10.43 (s, 1H, CH=N), 13.90 (s, 1H, SH). 13C NMR: 27.76, 35.39, 36.42, 38.63 (adamantane-C), 125.40, 126.87, 129.43, 133.54, 134.53, 149.29 (Ar-C), 156.26, 159.20 (triazole C-5 & CH=N), 162.65 (triazole C-3). MS, m/z (Rel. Int.): 384 (M+ +1, 7), 383 (M+, 24), 382 (100).

5-(1-Adamantyl)-4-(4-nitrobenzylideneamino)-3-mercapto-1,2,4-triazole 6m: 1H-NMR (DMSO-d6): δ 1.71 (s, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.06 (s, 6H, adamantane-H), 7.89 (d, 2H, Ar-H, J = 8.4 Hz), 8.32(d, 2H, Ar-H, J = 8.4 Hz), 10.21 (s, 1H, CH=N), 13.88 (s, 1H, SH). 13C NMR: 27.73, 35.21, 36.40, 38.61 (adamantane-C), 124.12, 128.83, 136.55, 150.22 (Ar-C), 155.66, 161.26 (triazole C-5 & CH=N), 162.85 (triazole C-3).

5-(1-Adamantyl)-4-(4-dimethylaminobenzylideneamino)-3-mercapto-1,2,4-triazole 6n: 1H-NMR (DMSO-d6): δ 1.66–1.71 (m, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.06 (s, 6H, adamantane-H), 3.04 (s, 6H, CH3), 6.83 (d, 2H, Ar-H, J = 8.5 Hz), 7.71 (d, 2H, Ar-H, J = 9.0 Hz), 9.21 (s, 1H, CH=N), 13.74 (s, 1H, SH). 13C NMR: 27.74, 35.18, 36.50, 38.55 (adamantane-C), 39.89 (CH3), 112.20, 119.31, 130.66, 153.72 (Ar-C), 155.88, 162.51 (triazole C-5 & CH=N), 165.99 (triazole C-3). MS, m/z (Rel. Int.): 382 (M+ +1, 8), 381 (M+, 36), 379 (100).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-3-mercapto-1,2,4-triazole 6o: 1H-NMR (DMSO-d6): δ 1.71 (s, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.09 (s, 6H, adamantane-H), 7.30–7.34 (m, 2H, Ar-H), 7.67-7.72 (m, 1H, Ar-H), 10.37 (s, 1H, CH=N), 13.87 (s, 1H, SH). 13C NMR: 27.30, 34.89, 35.87, 37.67 (adamantane-C), 109.74, 112.67, 134.86, 160.06 (Ar-C), 155.87, 160.06 (triazole C-5 & CH=N), 162.11 (triazole C-3). MS, m/z (Rel. Int.): 375 (M+ +1, 10), 374 (M+, 33), 343 (14), 236 (37), 235 (100), 234 (43), 220 (17), 139 (40), 135 (18), 126 (18), 113 (13).

5-(1-Adamantyl)-4-(2-chloro-6-fluorobenzylideneamino)-3-mercapto-1,2,4-triazole 6p: 1H-NMR (DMSO-d6): δ 1.71 (s, 6H, adamantane-H), 2.01 (s, 3H, adamantane-H), 2.09 (s, 6H, adamantane-H), 7.44–7.48 (m, 1H, Ar-H), 7.52 (d, 1H, Ar-H, J = 8.0 Hz), 7.63–7.67 (m, 1H, Ar-H), 10.54 (s, 1H, CH=N), 13.89 (s, 1H, SH). 13C NMR: 27.79, 35.41, 36.36, 38.23 (adamantane-C), 116.52, 119.14, 127.17, 134.57, 135.99, 162.59 (Ar-C), 156.41, 160.51 (triazole C-5 & CH=N), 162.21 (triazole C-3). MS, m/z (Rel. Int.): 392 (M+ +2, 8), 390 (M+, 20), 371 (12), 355 (22), 336 (9), 236 (56), 235 (100), 234 (18), 220 (26), 156 (33), 135 (14), 129 (7), 127 (22).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-3-mercapto-1,2,4-triazole 6q: 1H-NMR (DMSO-d6): δ 1.68 (s, 6H, adamantane-H), 1.99 (s, 3H, adamantane-H), 2.09 (s, 6H, adamantane-H), 7.53–7.68 (m, 3H, Ar-H), 10.63 (s, 1H, CH=N), 13.93 (s, 1H, SH). 13C NMR: 27.77, 35.48, 36.38, 38.38 (adamantane-C), 128.33, 130.42, 133.60, 135.32 (Ar-C), 156.43, 158.38 (triazole C-5 & CH=N), 162.46 (triazole C-3). MS, m/z (Rel. Int.): 410 (M+ +4, 4), 409 (M+ +3, 16), 408 (M+ +2, 18), 407 (M+ +1, 74), 406 (M+, 22), 405 (100).

5-(1-Adamantyl)-4-(2,4-dichlorobenzylideneamino)-3-mercapto-1,2,4-triazole 6r: 1H-NMR (DMSO-d6): δ 1.72 (s, 6H, adamantane-H), 2.03 (s, 3H, adamantane-H), 2.08 (s, 6H, adamantane-H), 7.67–7.69 (m, 1H, Ar-H), 7.84 (s, 1H, Ar-H), 8.12 (d, 1H, Ar-H, J = 8.0 Hz), 10.50 (s, 1H, CH=N), 13.89 (s, 1H, SH). 13C NMR: 27.76, 35.41, 36.49, 38.71 (adamantane-C), 128.91, 129.12, 129.49, 130.48, 136.44, 138.29 (Ar-C), 156.26, 157.41 (triazole C-5 & CH=N), 162.44 (triazole C-3). MS, m/z (Rel. Int.): 410 (M+ +4, 3), 409 (M+ +3, 15), 408 (M+ +2, 17), 407 (M+ +1, 69), 406 (M+, 22), 405 (100).

5-(1-Adamantyl)-4-(3,4-dichlorobenzylideneamino)-3-mercapto-1,2,4-triazole 6s: 1H-NMR (DMSO-d6): δ 1.70–1.72 (m, 6H, adamantane-H), 2.02 (s, 3H, adamantane-H), 2.06 (s, 6H, adamantane-H), 7.85–7.93 (m, 2H, Ar-H), 8.13 (s, 1H, Ar-H), 9.88 (s, 1H, CH=N), 13.86 (s, 1H, SH). 13C NMR: 27.74, 35.33, 36.47, 38.67 (adamantane-C), 128.34, 130.61, 132.19, 132.74, 133.40, 135.64 (Ar-C), 156.09, 161.65 (triazole C-5 & CH=N), 162.56 (triazole C-3). MS, m/z (Rel. Int.): 410 (M+ +4, 3), 409 (M+ +3, 15), 408 (M+ +2, 17), 407 (M+ +1, 73), 406 (M+, 23), 405 (100).

5-(1-Adamantyl)-4-(3,4-dimethoxybenzylideneamino)-3-mercapto-1,2,4-triazole 6t: 1H-NMR (DMSO-d6): δ 1.67–1.74 (m, 6H, adamantane-H), 2.02 (s, 3H, adamantane-H), 2.08 (s, 6H, adamantane-H), 3.84 (s, 3H, OCH3), 3.86 (s, 3H, OCH3), 7.15 (d, 1H, Ar-H, J = 8.5 Hz), 7.47 (d, 1H, Ar-H, J = 8.5 Hz), 7.50 (s, 1H, Ar-H), 9.56 (s, 1H, CH=N), 13.74 (s, 1H, SH). 13C NMR: 27.76, 35.28, 36.52, 38.64 (adamantane-C), 56.0 (OCH3), 56.28 (OCH3), 110.09, 112.34, 124.20, 125.25, 149.74, 153.35 (Ar-C), 156.01, 162.46 (triazole C-5 & CH=N), 164.54 (triazole C-3). MS, m/z (Rel. Int.): 399 (M+ +1, 7), 398 (M+, 24), 397 (100).

5-(1-Adamantyl)-4-(2,4-dinitrobenzylideneamino)-3-mercapto-1,2,4-triazole 6u: 1H-NMR (DMSO-d6): δ 1.72 (s, 6H, adamantane-H), 2.02 (s, 3H, adamantane-H), 2.08 (s, 6H, adamantane-H), 8.41 (d, 1H, Ar-H, J = 8.5 Hz), 8.65 (d, 1H, Ar-H, J = 8.5 Hz), 9.03 (s, 1H, Ar-H), 11.51 (s, 1H, CH=N), 13.46 (s, 1H, SH). 13C NMR: 27.80, 34.80, 36.52, 38.36 (adamantane-C), 120.79, 128.01, 129.52, 131.72, 135.05, 147.74 (Ar-C), 157.09, 157.86 (triazole C-5 & CH=N), 167.73 (triazole C-3). MS, m/z (Rel. Int.): 451 (M+ +Na, 4), 450 (11), 451 (48), 436 (100), 428 (M+, 3), 427 (10).

5-(1-Adamantyl)-4-(4,5-dimethoxy-2-nitrobenzylideneamino)-3-mercapto-1,2,4-triazole 6v: 1H-NMR (DMSO-d6): δ 1.70–1.74 (m, 6H, adamantane-H), 2.02 (s, 3H, adamantane-H), 2.10 (s, 6H, adamantane-H), 3.96 (s, 3H, OCH3), 3.97 (s, 3H, OCH3), 7.64 (s, 1H, Ar-H), 7.75 (s, 1H, Ar-H), 10.56 (s, 1H, CH=N), 13.86 (s, 1H, SH). 13C NMR: 27.77, 35.44, 36.49, 38.76 (adamantane-C), 56.67 (OCH3), 57.05 (OCH3), 108.73, 109.16, 120.95, 143.12, 151.89, 153.10 (Ar-C), 156.28, 157.92 (triazole C-5 & CH=N), 162.56 (triazole C-3). MS, m/z (Rel. Int.): 444 (M+ +1, 7), 443 (M+, 24), 442 (100).

5-(1-Adamantyl)-4-arylideneamino-2-(4-substituted-1-piperazinylmethyl)-1,2,4-triazoline-3-thiones

A mixture of the 5-(1-adamantyl)-4-(2,6-dihalobenzylideneamino)-3-mercapto-1,2,4-triazoles 6o or 6q (1.0 mmol), the appropriate N-substituted piperazine (1.0 mmol) and 37% formaldehyde solution (1 mL), in ethanol (8 mL), was heated under reflux for 15 min when a clear solution was obtained. Stirring was continued for 12 h at room temperature and the mixture was allowed to stand overnight. Cold water (5 mL) was added and the reaction mixture was stirred for 20 min. The precipitated crude products were filtered, washed with water, dried, and crystallized (Table 2).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-(4-methyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7a: 1H-NMR (CDCl3): 1.78 (s, 6H, adamantane-H), 2.08 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.30 (s, 3H, CH3), 2.47 (s, 4H, piperazine-H), 2.92 (s, 4H, piperazine-H), 5.18 (s, 2H, CH2), 7.02–7.07 (m, 2H, Ar-H), 7.46–7.48 (m. 1H, Ar-H), 10.64 (s, 1H, CH=N). 13C NMR: 27.95, 35.51, 36.45, 38.32 (adamantane-C), 46.05 (CH3), 55.05, 58.36 (piperazine-C), 68.68 (CH2), 110.87, 112.16, 133.21, 152.24 (Ar-C), 155.52, 160.99 (triazole C-5 & CH=N), 163.05 (C=S). MS, m/z (Rel. Int.): 488 (M+ +2, 30), 487 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-(4-ethyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7b: 1H-NMR (CDCl3): δ 1.07 (t, 3H, CH3, J = 7.0 Hz), 1.78 (s, 6H, adamantane-H), 2.08 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.40 (q, 2H, C2CH3, J = 7.0 Hz), 2.48–2.49 (m, 4H, piperazine-H), 2.92 (s, 4H, piperazine-H), 5.18 (s, 2H, CH2), 7.02 (t, 2H, Ar-H, J = 8.5 Hz), 7.44–7.48 (m. 1H, Ar-H), 10.62 (s, 1H, CH=N). 13C NMR: 11.91 (CH3), 28.0, 35.50, 36.46, 38.33 (adamantane-C), 52.32 (H2CH3), 50.42, 52.80 (piperazine-C), 68.79 (CH2), 110.89, 112.16, 133.20, 152.22 (Ar-C), 155.45, 161.0 (triazole C-5 & CH=N), 163.14 (C=S). MS, m/z (Rel. Int.): 502 (M+ +2, 32), 501 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7c: 1H-NMR (CDCl3): δ 1.24 (t, 3H, CH3, J = 7.0 Hz), 1.79 (s, 6H, adamantane-H), 2.09 (s, 3H, adamantane-H), 2.17 (s, 6H, adamantane-H), 2.81 (s, 4H, piperazine-H), 3.50 (s, 4H, piperazine-H), 4.10 (q, 2H, C2CH3, J = 7.0 Hz), 5.16 (s, 2H, CH2), 7.02 (t, 2H, Ar-H, J = 7.0 Hz), 7.46–7.50 (m. 1H, Ar-H), 10.64 (s, 1H, CH=N). 13C NMR: 14.62 (CH3), 27.98, 35.55, 36.43, 38.35 (adamantane-C), 50.37, 52.39 (piperazine-C), 61.32 (H2CH3), 68.97 (CH2), 110.81, 112.22, 133.29, 152.23 (Ar-C), 155.46, 155.70, 161.04 (C=O, triazole C-5 & CH=N), 163.20 (C=S). MS, m/z (Rel. Int.): 546 (M+ +2, 6), 445 (M+ +1, 20).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-(4-phenyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7d: 1H-NMR (CDCl3): δ 1.80 (s, 6H, adamantane-H), 2.10 (s, 3H, adamantane-H), 2.19 (s, 6H, adamantane-H), 3.04 (s, 4H, piperazine-H), 3.23 (s, 4H, piperazine-H), 5.24 (s, 2H, CH2), 6.89 (t, 1H, Ar-H, J = 7.0 Hz), 6.94 (d, 2H, Ar-H, J = 8.0 Hz), 7.03 (t. 2H, Ar-H, J = 8.5 Hz), 7.26–7.28 (m, 2H, Ar-H), 7.47–7.50 (m. 1H, Ar-H), 10.67 (s, 1H, CH=N). 13C NMR: 28.0, 35.56, 36.46, 38.37 (adamantane-C), 49.41, 50.55 (piperazine-C), 68.82 (CH2), 110.76, 112.19, 116.31, 119.88, 129.10, 133.27, 151.38, 152.24 (Ar-C), 155.64, 161.06 (triazole C-5 & CH=N), 163.22 (C=S). MS, m/z (Rel. Int.): 550 (M+ +2, 36), 549 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-[4-(4-fluorophenyl)-1-piperazinylmethyl]-1,2,4-triazoline-3-thione 7e: 1H-NMR (CDCl3): δ 1.80 (s, 6H, adamantane-H), 2.10 (s, 3H, adamantane-H), 2.19 (s, 6H, adamantane-H), 3.04 (s, 4H, piperazine-H), 3.14 (s, 4H, piperazine-H), 5.23 (s, 2H, CH2), 6.89–6.99 (m, 4H, Ar-H), 7.03 (t. 2H, Ar-H, J = 8.5 Hz), 7.48–7.49 (m, 1H, Ar-H), 10.66 (s, 1H, CH=N). 13C NMR: 28.0, 35.57, 36.46, 38.38 (adamantane-C), 50.40, 50.54 (piperazine-C), 68.78 (CH2), 110.85, 112.39, 115.41, 118.10, 133.28, 148.04, 152.24, 158.24 (Ar-C), 155.65 (CH=N), 161.06 (triazole C-5), 163.23 (C=S). MS, m/z (Rel. Int.): 568 (M+ +2, 33), 567 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-[4-(3-trifluoromethylphenyl)-1-piperazinylmethyl]-1,2,4-triazoline-3-thione 7f: 1H-NMR (CDCl3): δ 1.80 (s, 6H, adamantane-H), 2.10 (s, 3H, adamantane-H), 2.19 (s, 6H, adamantane-H), 3.03-3.04 (m, 4H, piperazine-H), 3.21-3.27 (m, 4H, piperazine-H), 5.24 (s, 2H, CH2), 7.04–7.13 (m, 5H, Ar-H), 7.34 (t. 1H, Ar-H, J = 8.0 Hz), 7.46–7.50 (m, 1H, Ar-H), 10.67 (s, 1H, CH=N). 13C NMR: 27.99, 35.57, 36.44, 38.38 (adamantane-C), 48.87, 50.36 (piperazine-C), 68.73 (CH2), 118.86 (CF3), 110.83, 112.36, 115.09, 123.22, 125.39, 129.53, 131.58, 133.31, 151.44, 152.27 (Ar-C), 155.71, 161.01 (triazole C-5 & CH=N), 163.25 (C=S). MS, m/z (Rel. Int.): 618 (M+ +2, 35), 617 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-[4-(2-methoxylphenyl)-1-piperazinylmethyl]-1,2,4-triazoline-3-thione 7g: 1H-NMR (CDCl3): δ 1.80 (s, 6H, adamantane-H), 2.10 (s, 3H, adamantane-H), 2.20 (s, 6H, adamantane-H), 3.10 (s, 8H, piperazine-H), 3.87 (s, 3H, OCH3), 5.25 (s, 2H, CH2), 6.86 (d, 1H, Ar-H, J = 7.5 Hz), 6.92–6.98 (m, 2H, Ar-H), 7.0–7.07 (m, 3H, Ar-H), 7.47–7.49 (m, 1H, Ar-H), 10.63 (s, 1H, CH=N). 13C NMR: 28.02, 35.55, 36.48, 38.34 (adamantane-C), 50.72, 50.83 (piperazine-C), 55.27 (OCH3), 69.04 (CH2), 110.03, 112.18, 112.38, 118.28, 120.94, 123.02, 133.23, 141.34, 152.26, 152.33 (Ar-C), 155.55, 161.02 (triazole C-5 & CH=N), 163.21 (C=S). MS, m/z (Rel. Int.): 580 (M+ +2, 33), 579 (M+ +1, 92).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-(4-benzyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7h: 1H-NMR (CDCl3): δ 1.80 (s, 6H, adamantane-H), 2.09 (s, 3H, adamantane-H), 2.18 (s, 6H, adamantane-H), 2.41–2.52 (m, 4H, piperazine-H), 2.95 (s, 4H, piperazine-H), 3.52 (s, 2H, PhC2), 5.17 (s, 2H, CH2), 7.03 (t, 2H, Ar-H, J = 8.5 Hz), 7.25–7.32 (m, 5H, Ar-H), 7.45–7.49 (m, 1H, Ar-H), 10.65 (s, 1H, CH=N). 13C NMR: 28.0, 35.52, 36.47, 38.36 (adamantane-C), 50.51, 53.12 (piperazine-C), 63.18 (PhH2), 68.96 (CH2), 110.89, 112.17, 127.04, 128.18, 129.29, 133.11, 137.96, 152.11 (Ar-C), 155.47, 161.05 (triazole C-5 & CH=N), 163.19 (C=S). MS, m/z (Rel. Int.): 564 (M+ +2, 34), 563 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-(4-methyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7i: 1H-NMR (CDCl3): δ 1.76 (s, 6H, adamantane-H), 2.07 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.33 (s, 3H, CH3), 2.50–2.54 (m, 4H, piperazine-H), 2.92–2.96 (m, 4H, piperazine-H), 5.17 (s, 2H, CH2), 7.22-7.48 (m, 3H, Ar-H), 10.80 (s, 1H, CH=N). 13C-NMR: 27.91, 35.54, 36.43, 38.44 (adamantane-C), 43.85 (CH3), 54.36, 56.42 (piperazine-C), 68.71 (CH2), 128.62, 129.43, 131.75, 136.18 (Ar-C), 155.42, 158.18 (triazole C-5 & CH=N), 163.44 (C=S). MS, m/z (Rel. Int.): 522 (M+ +4, 6), 520 (M+ +2, 55), 518 (M+, 100).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-(4-ethyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7j: 1H-NMR (CDCl3): δ 1.08 (t, 3H, CH3, J = 7.0 Hz), 1.75 (s, 6H, adamantane-H), 2.06 (s, 3H, adamantane-H), 2.16–2.17 (m, 6H, adamantane-H), 2.42 (q, 2H, C2CH3, J = 7.0 Hz), 2.52–2.53 (m, 4H, piperazine-H), 2.95 (s, 4H, piperazine-H), 5.19 (s, 2H, CH2), 7.32-7.37 (m, 1H, Ar-H), 7.42–7.47 (m. 2H, Ar-H), 10.74 (s, 1H, CH=N). 13C-NMR: 11.87 (CH3), 27.96, 35.55, 36.47, 38.51 (adamantane-C), 50.41 (H2CH3), 52.31, 52.76 (piperazine-C), 68.93 (CH2), 129.32, 129.40, 131.53, 136.10 (Ar-C), 155.41, 157.82 (triazole C-5 & CH=N), 163.42 (C=S). MS, m/z (Rel. Int.): 536 (M+ +4, 5), 534 (M+ +2, 43), 532 (M+, 100).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7k: 1H-NMR (CDCl3): δ 1.25 (t, 3H, CH3, J = 7.0 Hz), 1.76 (s, 6H, adamantane-H), 2.07 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.83 (s, 4H, piperazine-H), 3.51 (s, 4H, piperazine-H), 4.11 (q, 2H, C2CH3, J = 7.0 Hz), 5.17 (s, 2H, CH2), 7.30–7.36 (m, 1H, Ar-H), 7.41–7.46 (m. 2H, Ar-H), 10.79 (s, 1H, CH=N). 13C-NMR: 14.64 (CH3), 27.94, 35.61, 36.44, 38.52 (adamantane-C), 50.30, 52.50 (piperazine-C), 61.33 (H2CH3), 69.15 (CH2), 128.94, 129.37, 131.61, 136.09 (Ar-C), 155.30, 155.46, 157.76 (C=O, triazole C-5 & CH=N), 163.46 (C=S). MS, m/z (Rel. Int.): 599 (M+ +Na, 100), 577 (M+ +1, 7).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-(4-phenyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7l: 1H-NMR (CDCl3): δ 1.77 (s, 6H, adamantane-H), 2.08 (s, 3H, adamantane-H), 2.18 (s, 6H, adamantane-H), 3.06 (s, 4H, piperazine-H), 3.23 (s, 4H, piperazine-H), 5.25 (s, 2H, CH2), 6.87 (t, 1H, Ar-H, J = 7.5 Hz), 6.95 (d, 2H, Ar-H, J = 8.0 Hz), 7.27–7.37 (m, 4H, Ar-H), 7.46–7.47 (m, 1H, Ar-H), 10.80 (s, 1H, CH=N). 13C-NMR: 27.96, 35.61, 36.46, 38.54 (adamantane-C), 49.45, 50.60 (piperazine-C), 69.0 (CH2), 116.35, 119.92, 129.06, 129.11, 129.37, 131.60, 136.12, 151.39 (Ar-C), 155.61, 156.09, 157.83 (triazole C-5 & CH=N), 163.48 (C=S). MS, m/z (Rel. Int.): 585 (M+ +4, 16), 583 (M+ +2, 77), 581 (M+, 100).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-[4-(4-fluorophenyl)-1-piperazinylmethyl]-1,2,4-triazoline-3-thione 7m: 1H-NMR (CDCl3): δ 1.76 (s, 6H, adamantane-H), 2.08 (s, 3H, adamantane-H), 2.18 (s, 6H, adamantane-H), 3.05–3.06 (m, 4H, piperazine-H), 3.15 (s, 4H, piperazine-H), 5.24 (s, 2H, CH2), 6.88–6.91 (m, 2H, Ar-H), 6.96–6.99 (m, 2H, Ar-H), 7.33–7.36 (m, 1H, Ar-H), 7.45 (d, 2H, Ar-H, J = 7.0 Hz), 10.79 (s, 1H, CH=N). 13C-NMR: 27.96, 35.61, 36.46, 38.55 (adamantane-C), 50.44, 50.59 (piperazine-C), 68.95 (CH2), 115.43, 115.60, 118.08, 118.14, 129.37, 131.60, 136.11, 148.06 (Ar-C), 155.62, 157.83 (triazole C-5 & CH=N), 163.49 (C=S). MS, m/z (Rel. Int.): 602 (M+ +4, 23), 601 (M+ +3, 78), 600 (M+ +2, 32), 599 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-[4-(3-trifluoromethylphenyl)-1-piperazinylmethyl]-1,2,4-triazoline-3-thione 7n: 1H-NMR (CDCl3): δ 1.77 (s, 6H, adamantane-H), 2.08 (s, 3H, adamantane-H), 2.18 (s, 6H, adamantane-H), 3.05–3.06 (m, 4H, piperazine-H), 3.27–3.28 (m, 4H, piperazine-H), 5.24 (s, 2H, CH2), 7.07 (t, 2H, Ar-H, J = 8.5 Hz), 7.14 (s, 1H, Ar-H), 7.34–7.37 (m, 2H, Ar-H), 7.46 (d, 2H, Ar-H, J = 8.0 Hz), 10.80 (s, 1H, CH=N). 13C-NMR: 27.94, 35.62, 36.44, 38.55 (adamantane-C), 48.89, 50.40 (piperazine-C), 68.91 (CH2), 118.89 (CF3), 112.43, 115.98, 123.22, 125.39, 129.02, 129.39, 129.55, 131.78, 136.12, 151.44 (Ar-C), 155.68, 157.86 (triazole C-5 & CH=N), 163.50 (C=S). MS, m/z (Rel. Int.): 652 (M+ +4, 16), 651 (M+ +3, 76), 650 (M+ +2, 32), 649 (M+ +1, 100).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-[4-(2-methoxyphenyl)-1-piperazinylmethyl]-1,2,4-triazoline-3-thione 7o: 1H-NMR (CDCl3): δ 1.77 (s, 6H, adamantane-H), 2.08 (s, 3H, adamantane-H), 2.19 (s, 6H, adamantane-H), 3.11 (s, 8H, piperazine-H), 3.87 (s, 3H, OCH3), 5.26 (s, 2H, CH2), 6.86 (d, 1H, Ar-H, J = 7.5 Hz), 6.93–7.04 (m, 3H, Ar-H), 7.33–7.36 (m, 1H, Ar-H) 7.45 (d, 2H, Ar-H, J = 8.0 Hz), 10.76 (s, 1H, CH=N). 13C-NMR: 27.98, 35.59, 36.49, 38.51 (adamantane-C), 50.76, 50.84 (piperazine-C), 55.28 (OCH3), 69.22 (CH2), 110.98, 118.29, 120.93, 123.04, 129.12, 129.34, 131.55, 136.12, 141.32, 152.27 (Ar-C), 155.50 (triazole C-5), 157.89 (CH=N), 163.49 (C=S). MS, m/z (Rel. Int.): 614 (M+ +4, 9), 613 (M+ +3, 35), 612 (M+ +2, 14), 611 (M+ +1, 46).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-(4-benzyl-1-piperazinylmethyl)-1,2,4-triazoline-3-thione 7p: 1H-NMR (CDCl3): δ 1.76 (s, 6H, adamantane-H), 2.07 (s, 3H, adamantane-H), 2.17 (s, 6H, adamantane-H), 2.51 (s, 4H, piperazine-H), 2.92 (s, 4H, piperazine-H), 3.52 (s, 2H, PhC2), 5.17 (s, 2H, CH2), 7.26–7.36 (m, 6H, Ar-H), 7.45 (d, 2H, Ar-H , J = 8.0 Hz), 10.78 (s, 1H, CH=N). 13C-NMR: 27.96, 35.56, 36.47, 38.53 (adamantane-C), 50.53, 53.14 (piperazine-C), 63.24 (PhH2), 69.11 (CH2), 127.07, 128.20, 129.12, 129.33, 129.42, 131.54, 136.10, 137.90 (Ar-C), 155.45, 157.68 (triazole C-5 & CH=N), 163.45 (C=S). MS, m/z (Rel. Int.): 598 (M+ +4, 13), 597 (M+ +3, 76), 596 (M+ +2, 35), 595 (M+ +1, 100).

5-(1-Adamantyl)-4-arylideneamino-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thiones

A mixture of the 5-(1-adamantyl)-4-arylideneamino-3-mercapto-1,2,4-triazole 6 (1.0 mmol), ethyl 4-piperidinecarboxylate (0.16 g, 1.0 mmol) and 37% formaldehyde solution (1 mL), in ethanol (8 mL), was heated under reflux for 20 min when a clear solution was obtained. Stirring was continued for 12 h at room temperature and the mixture was allowed to stand overnight. Cold water (5 mL) was added and the reaction mixture was stirred for 20 min. The precipitated crude products were filtered, washed with water, dried, and crystallized (Table 3).

5-(1-Adamantyl)-4-benzylideneamino-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8a: 1H-NMR (CDCl3): δ 1.24 (t, 3H, CH3, J = 7.0 Hz), 1.72–1.83 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.94 (m, 2H, piperidine-H), 2.10 (s, 3H, adamantane-H), 2.17 (s, 6H, adamantane-H), 2.20–2.25 (m, 1H, piperidine-4 H), 2.46–2.50 (m, 2H, piperidine-H), 3.20–3.22 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.51–7.58 (m, 3H, Ar-H), 7.91 (d, 2H, Ar-H, J = 7.0 Hz), 10.08 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.93, 35.44, 36.58, 38.77 (adamantane-C), 28.35 (piperidine C-3), 40.42 (piperidine C-4), 50.42 (piperidine C-2), 60.25 (H2CH3), 69.63 (CH2), 128.72, 129.02, 132.28, 132.84 (Ar-C), 155.28, 162.26 (triazole C-5 & CH=N), 163.21 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): 509 (M+ +2, 21), 508 (M+ +1, 72).

5-(1-Adamantyl)-4-(2-fluorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8b: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.72–1.82 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.94 (m, 2H, piperidine-H), 2.10 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.20–2.25 (m, 1H, piperidine-4 H), 2.50–2.54 (m, 2H, piperidine-H), 3.19–3.22 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.18 (t, 1H, Ar-H, J = 8.0 Hz), 7.30 (d, 1H, Ar-H, J = 7.5 Hz), 7.53–7.56 (m, 1H, Ar-H), 8.08-8.11 (m, 1H, Ar-H), 10.42 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.93, 35.46, 36.56, 38.76 (adamantane-C), 28.35 (piperidine C-3), 40.77 (piperidine C-4), 50.42 (piperidine C-2), 60.25 (H2CH3), 69.64 (CH2), 116.31, 120.89, 124.66, 127.57, 133.90, 155.82 (Ar-C), 155.28, 161.54 (triazole C-5 & CH=N), 163.31 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): (M+ +2, 33), 526 (M+ +1, 100).

5-(1-Adamantyl)-4-(2-chlorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8c: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.72–1.79 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.94 (m, 2H, piperidine-H), 2.11 (s, 3H, adamantane-H), 2.17 (s, 6H, adamantane-H), 2.21–2.25 (m, 1H, piperidine-4 H), 2.51-2.55 (m, 2H, piperidine-H), 3.20–3.22 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.40 (t, 1H, Ar-H, J = 7.5 Hz), 7.46–7.51 (m, 2H, Ar-H), 8.19 (d, 1H, Ar-H, J = 7.5 Hz), 10.69 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.93, 35.49, 36.58, 38.83 (adamantane-C), 28.35 (piperidine C-3), 40.78 (piperidine C-4), 50.43 (piperidine C-2), 60.25 (H2CH3), 69.65 (CH2), 127.20, 127.60, 130.34, 130.85, 132.97, 136.68 (Ar-C), 155.28, 158.27 (triazole C-5 & CH=N), 163.37 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): 564 (M+ +Na, 100), 544 (23), 542 (54).

5-(1-Adamantyl)-4-(4-methylbenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8d: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.72–1.78 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.91–1.94 (m, 2H, piperidine-H), 2.09 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.20–2.25 (m, 1H, piperidine-4 H), 2.45 (s, 3H, PhC3), 2.50–2.54 (m, 2H, piperidine-H), 3.19–3.22 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.31 (d, 2H, Ar-H, J = 8.0 Hz), 7.80 (d, 2H, Ar-H, J = 8.0 Hz), 9.94 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 21.71 (PhH3), 27.93, 35.40, 36.58, 38.75 (adamantane-C), 28.35 (piperidine C-3), 40.78 (piperidine C-4), 50.41 (piperidine C-2), 60.24 (H2CH3), 69.62 (CH2), 128.75, 129.76, 130.10, 143.05 (Ar-C), 155.24, 162.69 (triazole C-5 & CH=N), 163.21 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): 544 (M+ +Na, 100), 523 (M+ +2, 43), 522 (M+ +1, 76).

5-(1-Adamantyl)-4-(2-hydroxybenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8e: 1H-NMR (CDCl3): δ 1.25 (t, 3H, C3CH2, J = 7.0 Hz), 1.73–1.79 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.95 (m, 2H, piperidine-H), 2.10 (s, 9H, adamantane-H), 2.22–2.24 (m, 1H, piperidine-4 H), 2.51–2.55 (m, 2H, piperidine-H), 3.19–3.21 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.03–7.06 (m, 1H, Ar-H), 7.08 (d, 1H, Ar-H, J = 8.5 Hz), 7.44–7.51 (m, 2H, Ar-H), 9.69 (s, 1H, CH=N), 10.45 (s, 1H, OH). 13C-NMR: 14.20 (CH3), 27.80, 35.35, 36.29, 38.97 (adamantane-C), 28.32 (piperidine C-3), 40.73 (piperidine C-4), 50.42 (piperidine C-2), 60.28 (H2CH3), 70.22 (CH2), 116.09, 117.56, 120.09, 133.60, 134.69, 169.08 (Ar-C), 154.28, 160.08 (triazole C-5 & CH=N), 164.01 (C=S), 174.94 (C=O). MS, m/z (Rel. Int.): 546 (M+ +Na, 100), 525 (M+ +2, 26), 524 (M+ +1, 84).

5-(1-Adamantyl)-4-(4-hydroxybenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8f: 1H-NMR (CDCl3): δ 1.25 (t, 3H, C3CH2, J = 7.0 Hz), 1.75–1.78 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.94–1.96 (m, 2H, piperidine-H), 2.07 (s, 3H, adamantane-H), 2.12 (s, 6H, adamantane-H), 2.24–2.28 (m, 1H, piperidine-4 H), 2.52–2.56 (m, 2H, piperidine-H), 3.21–3.23 (m, 2H, piperidine-H), 4.13 (q, 2H, C2CH3, J = 7.0 Hz), 5.14 (s, 2H, CH2), 6.92 (d, 2H, Ar-H, J = 8.5 Hz), 7.72 (d, 2H, Ar-H, J = 8.5 Hz), 9.55 (s, 1H, CH=N). 13C-NMR: 14.17 (CH3), 27.88, 35.37, 36.52, 38.66 (adamantane-C), 28.15 (piperidine C-3), 40.72 (piperidine C-4), 50.43 (piperidine C-2), 58.53 (H2CH3), 69.64 (CH2), 116.24, 124.64, 130.91, 163.01 (Ar-C), 155.38, 160.42 (triazole C-5 & CH=N), 164.17 (C=S), 175.32 (C=O). MS, m/z (Rel. Int.): 525 (M+ +2, 33), 524 (M+ +1, 100).

5-(1-Adamantyl)-4-(4-methoxybenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8g: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.72–1.79 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.91–1.93 (m, 2H, piperidine-H), 2.09 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.20–2.24 (m, 1H, piperidine-4 H), 2.50-2.53 (m, 2H, piperidine-H), 3.19–3.21 (m, 2H, piperidine-H), 3.90 (s, 3H, OCH3), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.02 (d, 2H, Ar-H, J = 8.5 Hz), 7.86 (d, 2H, Ar-H , J = 8.5 Hz), 9.81 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.93, 35.37, 36.58, 38.74 (adamantane-C), 28.35 (piperidine C-3), 40.79 (piperidine C-4), 55.48 (piperidine C-2), 60.23 (H2CH3), 69.64 (CH2), 114.54, 125.35, 130.59, 162.76 (Ar-C), 155.18, 162.69 (triazole C-5 & CH=N), 163.21 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): 560 (M+ +Na, 100), 539 (M+ +2, 38), 538 (M+ +1, 86).

5-(1-Adamantyl)-4-(2,6-difluorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8h: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.71–1.80 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.94 (m, 2H, piperidine-H), 2.09 (s, 3H, adamantane-H), 2.18 (s, 6H, adamantane-H), 2.21–2.25 (m, 1H, piperidine-4 H), 2.50–2.54 (m, 2H, piperidine-H), 3.19–3.21 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.14 (s, 2H, CH2), 7.03 (t, 2H, Ar-H, J = 8.5 Hz), 7.45–7.49 (m, 1H, Ar-H), 10.70 (s, 1H, CH=N). 13C-NMR: 14.19 (CH3), 28.0, 35.53, 36.46, 38.41 (adamantane-C), 28.35 (piperidine C-3), 40.77 (piperidine C-4), 50.42 (piperidine C-2), 60.25 (H2CH3), 69.43 (CH2), 110.89, 112.37, 133.21, 161.04 (Ar-C), 155.53, 160.99 (triazole C-5 & CH=N), 163.21 (C=S), 174.98 (C=O). MS, m/z (Rel. Int.): 566 (M+ +Na, 100), 545 (M+ +2, 18), 544 (M+ +1, 61).

5-(1-Adamantyl)-4-(2-chloro-6-fluorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8i: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.71–1.79 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.94 (m, 2H, piperidine-H), 2.09 (s, 3H, adamantane-H), 2.18 (s, 6H, adamantane-H), 2.21–2.25 (m, 1H, piperidine-4 H), 2.51–2.55 (m, 2H, piperidine-H), 3.20–3.22 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.14–7.17 (m, 2H, Ar-H), 7.33 (d, 1H, Ar-H, J = 7.5 Hz), 10.87 (s, 1H, CH=N). 13C-NMR: 14.19 (CH3), 28.0, 35.55, 36.46, 38.40 (adamantane-C), 28.36 (piperidine C-3), 40.77 (piperidine C-4), 50.43 (piperidine C-2), 60.24 (H2CH3), 69.46 (CH2), 115.35, 119.81, 126.25, 132.52, 137.10, 162.85 (Ar-C), 155.11 (CH=N), 160.76 (triazole C-5), 163.05 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): 582 (M+ +Na, 100), 562 (29), 561 (M+ +2, 21), 560 (M+ +1, 63).

5-(1-Adamantyl)-4-(2,6-dichlorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8j: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.72–1.81 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.95 (m, 2H, piperidine-H), 2.07 (s, 3H, adamantane-H), 2.17 (s, 6H, adamantane-H), 2.21–2.26 (m, 1H, piperidine-4 H), 2.53–2.57 (m, 2H, piperidine-H), 3.20–3.22 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 7.33–7.36 (m, 1H, Ar-H), 7.45 (d, 2H, Ar-H, J = 8.0 Hz), 10.84 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.96, 35.59, 36.46, 38.58 (adamantane-C), 28.36 (piperidine C-3), 40.77 (piperidine C-4), 50.44 (piperidine C-2), 60.24 (H2CH3), 69.62 (CH2), 128.77, 129.36, 131.54, 136.08 (Ar-C), 155.52, 157.56 (triazole C-5 & CH=N), 163.22 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): 598 (M+ +Na, 100), 578 (52), 577 (M+ +2, 23), 576 (M+ +1, 73).

5-(1-Adamantyl)-4-(2,4-dichlorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8k: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.72–1.83 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.91–1.94 (m, 2H, piperidine-H), 2.11 (s, 3H, adamantane-H), 2.16 (s, 6H, adamantane-H), 2.20–2.25 (m, 1H, piperidine-4 H), 2.50–2.54 (m, 2H, piperidine-H), 3.19–3.21 (m, 2H, piperidine-H), 4.12 (q, 2H, C2CH3, J = 7.0 Hz), 5.14 (s, 2H, CH2), 7.40 (d, 1H, Ar-H, J = 8.5 Hz), 7.53 (s, 1H, Ar-H), 8.11 (d, 1H, Ar-H, J = 8.5 Hz), 10.73 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.91, 35.50, 36.57, 38.86 (adamantane-C), 28.34 (piperidine C-3), 40.76 (piperidine C-4), 50.42 (piperidine C-2), 60.26 (H2CH3), 69.62 (CH2), 127.88, 128.28, 129.55, 130.16, 137.15, 138.58 (Ar-C), 155.23, 156.68 (triazole C-5 & CH=N), 163.33 (C=S), 174.96 (C=O). MS, m/z (Rel. Int.): 598 (M+ +Na, 100), 578 (56), 577 (M+ +2, 24), 576 (M+ +1, 78).

5-(1-Adamantyl)-4-(3,4-dichlorobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8l: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.71–1.84 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.91–1.93 (m, 2H, piperidine-H), 2.12 (s, 3H, adamantane-H), 2.15 (s, 6H, adamantane-H), 2.20–2.24 (m, 1H, piperidine-4 H), 2.49–2.53 (m, 2H, piperidine-H), 3.18–3.20 (m, 2H, piperidine-H), 4.11 (q, 2H, C2CH3, J = 7.0 Hz), 5.13 (s, 2H, CH2), 7.59 (d, 1H, Ar-H, J = 8.0 Hz), 7.72 (d, 1H, Ar-H, J = 8.0 Hz), 7.98 (s, 1H, Ar-H), 10.29 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.90, 35.50, 36.57, 38.86 (adamantane-C), 28.33 (piperidine C-3), 40.74 (piperidine C-4), 50.41 (piperidine C-2), 60.27 (H2CH3), 69.63 (CH2), 127.44, 130.03, 131.16, 133.01, 133.67, 136.40 (Ar-C), 155.25, 158.17 (triazole C-5 & CH=N), 163.20 (C=S), 174.94 (C=O). MS, m/z (Rel. Int.): 598 (M+ +Na, 100), 577 (M+ +2, 20), 576 (M+ +1, 67).

5-(1-Adamantyl)-4-(3,4-dimethoxybenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8m: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.76-1.82 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.91-1.93 (m, 2H, piperidine-H), 2.09 (s, 3H, adamantane-H), 2.17 (s, 6H, adamantane-H), 2.20-2.24 (m, 1H, piperidine-4 H), 2.49-2.54 (m, 2H, piperidine-H), 3.19-3.21 (m, 2H, piperidine-H), 3.96 (s, 3H, OCH3), 3.98 (s, 3H, OCH3), 4.11 (q, 2H, C2CH3, J = 7.0 Hz), 5.15 (s, 2H, CH2), 6.79 (d, 1H, Ar-H, J = 8.0 Hz), 7.40 (d, 1H, Ar-H, J = 8.0 Hz), 7.54 (s, 1H, Ar-H), 9.85 (s, 1H, CH=N). 13C-NMR: 14.19 (CH3), 27.94, 35.39, 36.61, 38.80 (adamantane-C), 28.35 (piperidine C-3), 40.78 (piperidine C-4), 50.41 (piperidine C-2), 55.92 (OCH3), 56.08 (OCH3), 60.24 (H2CH3), 69.63 (CH2), 109.19, 110.96, 124.42, 125.61, 149.60, 152.98 (Ar-C), 155.13, 162.48 (triazole C-5 & CH=N), 163.18 (C=S), 174.98 (C=O). MS, m/z (Rel. Int.): 590 (M+ +Na, 100), 569 (M+ +2, 26), 568 (M+ +1, 84).

5-(1-Adamantyl)-4-(4,5-dimethoxy-2-nitrobenzylideneamino)-2-(4-ethoxycarbonyl-1-piperidylmethyl)-1,2,4-triazoline-3-thione 8n: 1H-NMR (CDCl3): δ 1.24 (t, 3H, C3CH2, J = 7.0 Hz), 1.73–1.80 (m, 8H, 6 adamantane-H & 2 piperidine-H), 1.92–1.94 (m, 2H, piperidine-H), 2.08 (s, 3H, adamantane-H), 2.15 (s, 6H, adamantane-H), 2.21–2.23 (m, 1H, piperidine-4 H), 2.51–2.55 (m, 2H, piperidine-H), 3.18–3.21 (m, 2H, piperidine-H), 4.04 (s, 3H, OCH3), 4.05 (s, 3H, OCH3), 4.11 (q, 2H, C2CH3, J = 7.0 Hz), 5.14 (s, 2H, CH2), 7.65 (s, 1H, Ar-H), 7.63 (s, 1H, Ar-H), 10.54 (s, 1H, CH=N). 13C-NMR: 14.20 (CH3), 27.89, 35.42, 36.51, 38.81 (adamantane-C), 28.34 (piperidine C-3), 40.75 (piperidine C-4), 50.41 (piperidine C-2), 56.60 (OCH3), 56.68 (OCH3), 60.25 (H2CH3), 69.85 (CH2), 107.82, 110.0, 122.50, 142.33, 151.45, 153.30 (Ar-C), 155.03, 160.57 (triazole C-5 & CH=N), 163.57 (C=S), 174.99 (C=O). MS, m/z (Rel. Int.): 635 (M+ +Na, 100), 614 (M+ +2, 23), 613 (M+ +1, 68).

Determination of the antimicrobial activity by the agar disc-diffusion method. Sterile filter paper discs (8 mm diameter) were moistened with the compound solution in dimethylsulphoxide of specific concentration (200 μg/disc), the antibacterial antibiotics Gentamicin and Ampicillin trihydrate (100 μg/disc) and the antifungal drug Clotrimazole (100 μg/disc) were carefully placed on the agar culture plates that had been previously inoculated separately with the microorganisms. The plates were incubated at 37 ºC, and the diameter of the growth inhibition zones were measured after 24 h in case of bacteria and 48 h in case of Candida albicans.

Determination of minimal inhibitory concentration (MIC). Compounds 6h, 6o, 7n, 8a, 8e, 8f and 8m, Gentamicin, Ampicillin trihydrate and Clotrimazole were dissolved in dimethylsulphoxide at concentration of 128 μg/mL. The twofold dilutions of the solution were prepared (128, 64, 32, …, 0.5 μg/mL). The microorganism suspensions at 106 CFU/mL (colony forming unit/ml) concentrations were inoculated to the corresponding wells. The plates were incubated at 36 ºC for 24 and 48 h for the bacteria and Candida albicans, respectively. The MIC values were determined as the lowest concentration that completely inhibited visible growth of the microorganism as detected by unaided eye.

Determination of the anti-inflammatory activity. Male Sprague-Dawley rats weighing 140–190 g were maintained at room temperature (20–23 ºC). The animals were randomly divided into 42 groups each of 5 animals. The animals were housed with food and water ad libitum and allowed to be accustomed to their environment for two days before testing. Each group was injected with the specific dose of the test compound (20 and 40 mg/kg), or Indomethacin (5 mg/kg) intraperitoneally as a uniform suspension in 1 ml of 0.5% (w/v) aqueous carboxymethyl cellulose solution, one hour before injection of 0.1 mL of carrageenan (1% solution in normal saline) into the plantar tissue of the right hind paw. The left hind paw was injected with 0.1 mL of normal saline solution. Four hours after carrageenan injection, the volume of paw oedema (mL) was determined using water plethysmometer. The percentage protection against inflammation was calculated as follows:

Where Vc is the mean percentage increase in paw volume in the absence of the test compound (control) and Vd is the mean percentage increase in paw volume after injection of the test compound. The values are expressed as the mean percentage reduction ± S.E.M. Statistical significance between the control and treated groups was performed using the Student “t” test.

4. Conclusions

In this study, new series of 5-(1-adamantyl)-4-arylideneamino-3-mercapto-1,2,4-triazoles 6a-v , the N-Mannich bases 5-(1-adamantyl)-4-arylideneamino-2-(4-substituted-1-piperazinylmethyl)-1,2,4-triazoline-3-thiones 7a–p and 5-(1-adamantyl)-4-arylideneamino-2-(4-ethoxycarbonyl-1-piperidyl-methyl)-1,2,4-triazoline-3-thiones 8a-n, were synthesized and their antimicrobial and anti-inflammatory activity was determined. Several of the newly synthesized derivatives displayed promising antimicrobial and anti-inflammatory activities compared to known antibacterial, antifungal and anti-inflammatory drugs. Though, the mechanism of the biological activity needs further investigations, which are in progress.