Phosphatase CDC25B Inhibitors Produced by Basic Alumina-Supported One-Pot Gram-Scale Synthesis of Fluorinated 2-Alkylthio-4-aminoquinazolines Using Microwave Irradiation.

An efficient, environmentally benign, and inexpensive procedure has been developed for the synthesis of fluorinated 2-alkylthio-4-aminoquinazolines by microwave irradiation using basic alumina as a solid-support agent as well as a solid base. Notably, this protocol features improved energy efficiency, broad isothiourea substrate scope, easily available starting materials, and high atom efficiency and applicability toward gram-scale synthesis. Additionally, the target compounds were evaluated for the cytotoxic effect against human colon adenocarcinoma (HCT116 and HT29), human gastric cancer (SGC-7901), human lung adenocarcinoma (A549), and human hepatocyte carcinoma (HepG2) cells, and it was found that these compounds have excellent antitumor activities. Among them, compound 3e was found to be one of the most potent derivatives with IC50 values lower than 9.44 μM against five human tumor cell lines, making it more active than cisplatin (DDP). Furthermore, for the first time, the fluorinated 2-alkylthio-substituted 4-aminoquinazolines were identified as phosphatase CDC25B inhibitors.

Introduction

One of the vital and sensible alternatives of organic synthesis is necessary to develop new methods to achieve greener chemical processes.[1−8] Recently, green synthesis has been encouraged by the search for eco-friendly reaction media or solvent-free to replace commonly used volatile and hazardous organic solvents as well as to avoid the use of toxic and complex catalytic systems.[9−15] Moreover, more efficient microwave sources are being used to improve the energy efficiency in the chemical process.[16−21]

Quinazolines are an important class of N-containing heterocyclic compounds that have increasingly attracted considerable attention because of their diverse pharmacological activities, and they can be used as spinal muscular atrophy therapeutics,[22] antiatrial fibrillation agents,[23] anticancer drugs,[24−28] antimalarial agents,[29] etc.[30−32] In particular, as one of the diverse quinazoline derivatives, 4-aminoquinazoline nucleus is commonly present in a variety of drug molecules and biologically active agents.[30−33] For example, gefitinib (Iressa)[34,35] and lapatinib (Tykerb)[36] have been extensively used as inhibitors of tyrosine kinases for the treatment of nonsmall cell lung cancer and breast cancer, respectively (Figure ). CCT241533 blocked checkpoint kinase 2 activity in human tumor cell lines in response to DNA damage (Figure ).[37] Prazosin (Minipress) had effective α-adrenergic blocking activity, which is thus useful as antihypertensive medication (Figure ).[38,39] Many attempts have been made over the last few decades to introduce a combinatorial library of 4-aminoquinazolines.[30−32] Because of the value and importance of the sulfur-containing compounds in pharmaceuticals,[40] introducing different thioether groups into the 4-aminoquinazoline moiety would be of great synthetic value. However, the preparation of 2-alkylthio-4-aminoquinazoline derivatives has only been reported in a limited number of cases. The main synthetic methods can be summarized as follows: (1) the nucleophilic addition/cyclization reaction of anthranilonitriles with isothiocyanate derivatives[41,42] or N-[bis(methylthio)methylene]-amino ester[43] and (2) alternatively, 2-alkylthio-4-aminoquinazolines can be prepared by the decoration of the existing quinazoline nucleus.[44] Despite the values of these methods, most of them were developed without concern for environmental consequences and involve the use of hazardous and volatile solvents, strong basic or toxic catalysts, and multistep reaction processes (Scheme , eq 1). In addition, the sulfur-containing substrate scope of these methods is limited. Therefore, a search for more efficient and environmentally benign procedures for the synthesis of pharmacologically potent 2-alkylthio-4-aminoquinazolines remains a valid objective in organic, medicinal, and combinatorial chemistry.

Figure 1

Biologically active 4-aminoquinazolines and targeted compounds.

Scheme 1

Mechanism Hypotheses for the Synthesis of Target Compounds 3

Polyfluoro benzenedicarbonitriles are a class of interesting and versatile synthetic building blocks for the construction of various fluorinated compounds[45−52] or synthetic materials in organic synthesis.[53] Some of these fluorinated compounds possess anticancer,[45−49] anti-HIV, or antibacterial[50−52] biological activity. Fluorine incorporation into biologically active compounds can alter drug metabolism or enzyme substrate recognition.[54−56] The hydrophobic nature of fluorinated compounds has also been cited for their ability to improve the transport across the blood–brain barrier. Because of the unique effects of F-substituents in pharmaceutical formulations, the use of fluorinated compounds as bioactive or functional molecules has recently increased. Additionally, polyfluoro benzenedicarbonitriles are used as the raw material to introduce fluorine and cyanide in target compounds so that fluoro and cyano groups can be derived to subsequently generate a molecular diversity of 4-aminoquinazoline derivatives.

Considering the above studies and in continuation of our interest in the synthesis of fluorinated fused-ring compounds with pharmacological activity,[45−52] herein, we report an environmentally benign method and a new alternative route for the synthesis of 2-alkylthio-4-aminoquinazolines, with a broader sulfur-containing substrate scope, through a microwave-assisted solid-phase heterogeneous reaction (Scheme ). To the best of our knowledge, the synthesis of 2-alkylthio-4-aminoquinazolines derivatives has not been reported by the cyclization reaction of o-fluorobenzonitriles with S-substituted isothiouronium salts.

Results and Discussion

S-Alkyl isothiouronium salts 2 are environmentally benign and inexpensive, as they are readily produced by the reaction of thiourea with the appropriate alkyl halides[57,58] (Supporting Information). Accordingly, S-butyl isothiourea hydrobromide 2a was chosen as a model substrate to react with 2,4,5,6-tetrafluoro-isophthalonitrile 1a (Table ).

Table 1

Optimization of the Reaction Condition

entry	solvent or solid support	base	t (°C)	time (min)	yielde (%)
1	DMSO	K2CO3	120a	240	48
2	CH3CN	K2CO3	refluxa	300	33
3	1,4-dioxane	K2CO3	refluxa	240	50
4	1,4-dioxane	t-BuOK	refluxa	180	23
5	1,4-dioxane	Cs2CO3	refluxa	240	52
6	1,4-dioxane		refluxa	300	N.R.
7	Al2O3(basic,2 g)		80 (MW)b	20	82
8	Al2O3 (basic, 3 g)		80 (MW)b	20	77
9	Al2O3 (basic, 2 g)		80 (MW)c	20	80
10	Al2O3 (basic, 2 g)		80d	360	61
11	silica gel		120 (MW)b	20	N.R.
12	neutral alumina		120 (MW)b	20	N.R.

Conventional reaction conditions: the reaction was carried out using 2,4,5,6-tetrafluoroisophthalonitrile 1a (1.0 mmol), S-butyl isothiourea hydrobromide 2a (1.3 mmol), base (1.0 mmol), and solvent (10 mL).

Microwave-assisted reaction conditions: a mixture of 1a (1 mmol) and 2a (1.3 mmol) was adsorbed on a solid support (2 or 3 g) with the help of ethanol. The reaction mixture was irradiated in a microwave reactor (600 W).

Microwave-assisted reaction conditions: a mixture of 1a (1 mmol) and 2a (1.5 mmol) was adsorbed on a solid support (2 or 3 g) with the help of ethanol. The reaction mixture was irradiated in a microwave reactor (600 W).

The reaction was performed in an oil bath.

Isolated yield based on 1a.

Initially, when the reaction was conducted in the presence of 1 equiv K2CO3 at 120 °C in dimethyl sulfoxide (DMSO), the desired product, 2-(butylthio)-4-aminoquinazoline derivative 3a, was obtained with a yield of 48% (entry 1). This result motivated us to test different solvents and bases. However, acetonitrile and 1,4-dioxane did not clearly improve the yield of 3a (Table , entry 2 vs entries 2–3). Compared with K2CO3, t-BuOK and Cs2CO3 provided lower and slightly improved yields, respectively (Table , entry 3 vs entries 4–5). Additionally, the reaction did not proceed smoothly in the absence of a base (Table , entry 6). These findings led us to find a newer protocol that combines the use of basic alumina and microwave irradiation. Basic alumina is a widely used heterogeneous catalyst and has gained prominence in several areas of organic synthesis.[19,59,60] A mixture of 1a and 2a was adsorbed onto basic alumina (2 or 3 g) using ethanol as the solvent. The reaction mixture was irradiated in a microwave reactor for 20 min. The result showed that the microwave condition used can considerably improve the product yield (82%, Table , entries 7–9 vs entry 10). In contrast, no product was observed when the reaction was adsorbed onto the surface of a silica gel and neutral alumina (Table , entries 11 and 12). The results additionally revealed that basic alumina is the most adaptable support, which also acts as a solid base promoter for the synthesis of 3a, as indicated by the comparatively higher yield achieved in a shorter time (Table , entry 7). The use of a low-cost solid support eliminates the need for any external basic catalyst as required under thermal conditions.

Under the optimized reaction conditions, we investigated the scope of the reaction involving polyfluoro benzenedicarbonitriles (1a, 1b) with various substituted isothiouronium salts 2. In the cases where the reaction was completed, there were no great discrepancies in the reactivity and product yield for 1a and 1b (Table ). The data in Table reveal that the S-alkyl/alkyl ethers isothiouronium salts were all good substrates for the cyclization reaction under the microwave-assisted condition and produced the appropriate 2-alkylthio-4-aminoquinazolines 3a–3l within 20 min. In general, short carbon chain isothiouronium salts often produced higher yields than those with long carbon chain (Table ). When the S-benzyl/naphthalen-2-ylmethyl/allyl/cyanomethyl isothiouronium salts were used as substrates for the cyclization reaction under the same condition, the yield of the target product was good with shorter reaction time (Table , 3m–3x). In an effort to expand the scope of substrates 1, tetrafluoroterephthalonitrile 1c was reacted with different substituted isothiouronium salts 2. Compared with 1a–1b, the reaction can also provide the target compounds 3y–3c′ with moderate yields, but both the reaction temperature and time had to be increased (Table vs 3).

Table 2

Preparation of 2-Alkylthio-4-aminoquinazolinesa,b3a–3x

Reaction conditions: a mixture of polyfluoro benzenedicarbonitriles 1 (1.0 mmol) and isothiouronium salts 2 (1.3 mmol) was adsorbed on a solid support (2 g) with the help of ethanol. The reaction mixture was irradiated in a microwave reactor.

Isolated yield based on 1.

Table 3

Preparation of 2-Alkylthio-4-aminoquinazolinesa,b3y–3c′

Reaction conditions: a mixture of tetrafluoroterephthalonitrile 1c (1.0 mmol) and isothiouronium salts 2 (1.3 mmol) was adsorbed on a solid support (2 g) with the help of ethanol. The reaction mixture was irradiated in a microwave reactor.

Isolated yield based on 1c.

The feasibility of the present method was also examined for a somewhat scaled-up (on the gram scale) experiment: a mixture of 2,4,5,6-tetrafluoroisophthalonitrile 1a (2.00 g 10 mmol) and S-methyl isothiourea hydroiodide 2e (2.83 g 13 mmol) was adsorbed onto basic alumina (20 g) using ethanol as the solvent. The reaction mixture was then irradiated in a microwave reactor for 20 min. The reaction was found to proceed smoothly, producing the desired product 2-(methylthio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3e), with a yield of 78% (2.10 g), which was similar in all respects with the 1 mmol scale entry (Table , 3e). This result demonstrated the efficiency of the solid support for gram-scale production as well.

The 1H NMR, 13C NMR spectra, IR spectra, and high-resolution mass spectra analysis data confirmed the structure of the target compounds 3. To specifically determine the structure, 3e was characterized by X-ray crystallography as a representative compound, as shown in Figure (CCDC 1568305).

Figure 2

X-ray crystal structure of 3e (ellipsoids are drawn at the 30% probability level).

According to the above results, the promising performance of basic alumina could be attributed to the presence of Al–OH groups on the alumina surface.[61,62] Thus, we reasoned that basic alumina would be effective as a promoter in the reaction process because it may involve the formation of the hydrogen-bond interaction of the nitrile group of intermediate 6 with the surface hydroxyl group on the basic alumina. Accordingly, we propose a plausible mechanism for the formation of 4-aminoquinazolines 3 (Scheme ). The first step involves the release of free isothiourea compounds 4 from the adsorption reaction of its hydrogen halide with basic alumina. The second step is the nucleophilic aromatic substitution at o-fluoro of the polyfluoro benzenedicarbonitriles 1, which is promoted by basic alumina, to generate intermediate 5. Then, benzonitrile is activated by the surface O–H group on the basic alumina followed by the N-nucleophilic amine attacks on the nitrile group to form intermediate 7. Last, intermediate 7 was used to obtain target compound 3 by tautomerization.

Scheme 2

Mechanism Hypotheses for the Synthesis of Target Compounds 3

We selected 17 of the 2-alkylthio-4-aminoquinazoline derivatives to evaluate the in vitro antitumor activity against a series of human cells according to a previously reported method.[63] The tumor cell lines chosen were colon adenocarcinoma (HCT116 and HT29), gastric cancer (SGC-7901), lung adenocarcinoma (A549), and hepatocyte carcinoma (HepG2) cells. Cisplatin (DDP) was used as the reference drug. The results of the cytotoxicity analysis data are summarized in Table (IC50). As shown in Table , most of the compounds exhibited excellent antitumor activity against the cancer cells. Indeed, 3a, 3e–3h, 3j–3l, 3n, 3q, 3r, 3w, and 3x are more active than cisplatin against HCT116 cells (Table , entries 1 and 5–16); 3a, 3e–3h, 3j–3l, 3q, 3w, and 3x are more active than cisplatin against HT29 cells (Table , entries 1, 5–11, 13, 15, and 16); 3e–3h, 3j, 3k, 3l, 3n, 3q, 3w, and 3x are more active than cisplatin against SGC-7901 cells (Table , entries 5–9, 11–13, 15, and 16). These data indicate that most of the 2-alkythio-4-aminoquinazoline derivatives are usually most active against the colon adenocarcinoma (HCT116 and HT29) and gastric cancer (SGC-7901) cells, whereas the 2-(octylthio)-4-aminoquinazoline derivatives are usually less active against HCT116, HT29, and SGC-7901 cells (Table , entries 3 and 4). Only three compounds, namely, 3e, 3w, and 3x, are more active than cisplatin against HepG2 cells (Table , entries 5, 15, and 16). Seven compounds, 3e–3h, 3j, 3l, and 3x, are more active than cisplatin against A549 cells (Table , entries 5–9, 11, and 16). Among them, compounds 3e and 3x were more potent against all the tumor cell lines (HCT116, HT29, SGC-7901, A549, and HepG2) than cisplatin (DDP) (Table , entries 5 and 16). These results reveal that 2-alkylthio-4-aminoquinazoline derivatives also have good inhibitory activity against HCT116, HT29, A549, HepG2, and SGC-7901 cells. Additionally, the substituted group also has an influence on the cytotoxic activities. In general, the contribution order of the groups of 2-alkylthio-4-aminoquinazolines to cytotoxic activities was methyl ≈ naphthalen-2-ylmethyl ≈ 2-(2-methoxy-ethoxy)ethyl ≈ (tetrahydrofuran-2-yl)methyl > 2-methoxyethyl ≈ allyl ≈ benzyl ≈ n-butyl > n-octyl (Scheme ).

Table 4

Cytotoxic Activities of Target Compounds 3 in Vitroa (IC50, μMb)

no.	compd.	HCT116	HT29	SGC7901	A549	HepG2
1	3a	6.32	8.00	11.63	41.07	34.08
2	3b	16.03	59.36	30.36	>100	69.50
3	3c	55.05	>100	73.46	>100	>100
4	3d	>100	>100	>100	>100	>100
5	3e	4.56	4.75	6.09	9.44	5.09
6	3f	5.08	6.77	6.65	12.27	23.94
7	3g	5.55	4.93	5.68	6.50	14.89
8	3h	5.68	6.35	5.84	6.03	14.91
9	3j	6.94	7.97	7.34	7.48	34.03
10	3k	5.68	9.62	12.16	26.40	24.11
11	3l	4.39	6.87	5.45	6.00	26.12
12	3n	5.02	14.23	6.34	18.82	31.64
13	3q	4.89	6.06	6.26	24.80	12.25
14	3r	6.71	35.52	25.01	65.02	48.93
15	3w	3.84	5.80	5.89	26.42	6.41
16	3x	5.63	6.54	6.55	9.28	7.27
17	3y	9.32	35.68	20.97	70.53	51.79
18	cisplatin (DDP)	8.74	12.78	11.00	15.31	9.94

Cytotoxicity as IC50 for each cell line is the concentration of compound which reduced by 50% the optical density of treated cells with respect to untreated cells using the 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide assay.

Data represent the mean values of three independent determinations.

Scheme 3

Structure–Activity Relationship of 2-Alkythio-4-aminoquinazolines 3

Overexpression of CDC25B is frequently found in many cancers, such as colorectal cancer, gastric cancer, lung cancer, hepatocellular carcinoma, and so forth. Thus, the inhibition of CDC25B may represent a novel approach for the development of anticancer therapeutics.[64−66] For one thing, it is encouraged by the above findings. For another thing, the planar conformation and structural feature of 2-alkylthio-4-aminoquinazoline will contribute to this molecule acting on the cell division cycle 25B dual specificity phosphatase (CDC25B).[67−69] What is more, to the best of our knowledge, no inhibition against CDC25B activity has been reported with 4-aminoquinazoline scaffold. Accordingly, the new compounds 3 were screened for their inhibitory activities against CDC25B using an in vitro fluorimetric assay described in the literature.[70,71] As shown in Table , except for compounds 3g, 3h, and 3v (Table , entries 7, 8, and 22), most of the 2-alkylthio-4-aminoquinazoline derivatives showed a considerable inhibitory activity against CDC25B at a concentration of 20 μg/mL (Table , entries 1–6, 9–21, and 23–29). In order to evaluate the inhibitory activity more accurately, we selected 17 compounds from the preliminary screened results to evaluate the in vitro IC50 value against CDC25B (Table , entries 2–4, 9–11, 13, 14, 17–20, 23–25, 28, and 29). In all cases, good CDC25B inhibitory activity was observed. In particular, compounds 3b, 3n, 3t, and 3w (Table , entries 2, 14, 20, and 23) showed potent inhibitory activity against CDC25B (IC50 < 0.50 μg/mL) and close to the reference compound Na3VO4. These results reveal that 2-alkylthio-4-aminoquinazoline derivatives represent a new class of inhibitors against CDC25B.

Table 5

Inhibition of Target Compounds against CDC25B

entry	compound	CDC25B inhibition rate/%a	CDC25B IC50b/(μg/mL)
1	3a	94.32 ± 1.25	N.D.c
2	3b	99.55 ± 0.13	0.45 ± 0.04
3	3c	99.74 ± 0.12	2.67 ± 0.29
4	3d	97.31 ± 0.29	1.04 ± 0.02
5	3e	55.11 ± 1.72	N.D.c
6	3f	89.73 ± 1.14	N.D.c
7	3g	3.30 ± 1.55	N.D.c
8	3h	20.44 ± 8.93	N.D.c
9	3i	96.59 ± 0.68	1.24 ± 0.18
10	3j	98.64 ± 0.10	0.76 ± 0.15
11	3k	99.88 ± 0.11	1.50 ± 0.15
12	3l	78.25 ± 3.26	N.D.c
13	3m	99.64 ± 0.10	1.39 ± 0.25
14	3n	98.75 ± 0.05	0.39 ± 0.05
15	3o	80.39 ± 4.39	N.D.c
16	3p	73.75 ± 5.23	N.D.c
17	3q	96.33 ± 0.16	1.35 ± 0.19
18	3r	99.65 ± 0.01	0.93 ± 0.17
19	3s	99.59 ± 0.24	0.97 ± 0.10
20	3t	97.28 ± 0.16	0.42 ± 0.05
21	3u	83.27 ± 1.22	N.D.c
22	3v	2.11 ± 2.74	N.D.c
23	3w	99.40 ± 0.09	0.47 ± 0.02
24	3x	93.95 ± 1.03	0.58 ± 0.03
25	3y	96.64 ± 0.40	2.12 ± 0.10
26	3z	78.03 ± 1.97	N.D.c
27	3a′	63.42 ± 3.14	N.D.c
28	3b′	98.21 ± 0.04	2.42 ± 0.16
29	3c′	99.04 ± 0.06	0.85 ± 0.05
30	Na3VO4	N.D.c	0.13 ± 0.02

Inhibition % at 20 μg/mL concentration.

IC50 value: substance concentration necessary for 50% inhibition of CDC25B viability.

N.D. not determined.

On the basis of the target compounds 3, excellent antitumor activity was exhibited against HTC116 cells (Table ). We chose three compounds (3j, 3n, and 3w) with distinct 2-alkylthio differences to investigate the distribution of the cell-cycle progression of HTC116. Cells were treated with different doses of 3j, 3n, and 3w (1.02 or 2.56 μM) and DMSO for 24 h. Untreated cells were used as controls, and they exhibited a normal cell-cycle distribution (Figure a). Compared with the control cells, the percentage of cells in the G1 phase was significantly increased in the cells incubated with 1.02 μM compounds 3j and 3n (Figure b,c). The fraction of cells in the S phase decreased accordingly, while the proportion of G2/M phase cells showed no obvious change (Table ). Our data suggest that compounds 3j and 3n may induce cancer cell apoptosis via arresting the cells at the G1 phase in the cell cycle. In contrast, 2.56 μM 3w blocked cell passage through the G2-M phase in HCT116 cells (Figure d). The fraction of cells in the G1 phase decreased accordingly, while the proportion of S phase cells showed no obvious change (Table ). This G2-M arrest occurred only with compound 3w and was not observed with two other structural analogues (3j, 3n). These results suggested that the inhibition potency for CDC25B phosphatases is well-correlated with G1[69,72] or G2/M-arresting activity in HCT116 cells.

Figure 3

(a) Untreated cells were used as controls; (b,c) compounds 3j and 3n induce G1 phase arrest; and (d) 3w induces G2-M phase arrest in HTC116 cells. Cells were treated with 1.02 μM of compounds 3j and 3n and 2.56 μM of compound 3w for 24 h. The cell cycle was determined by DAPI staining and analyzed with a GE IN cell 2200 cell imaging system.

Table 6

Percentages of Cells in Different Phases Were Quantified

	cells (%)
treatment	G1	S	G2/M
DMSO	38.64	12.82	33.13
compd. 3j (1.02 μM)	49.55	7.55	29.95
compd. 3n (1.02 μM)	47.73	8.33	31.06
compd. 3w (2.56 μM)	25.23	11.10	51.84

To confirm CDC25B inhibition at the cellular level, the phosphorylation status of CDK1, which is a substrate of CDC25s, was analyzed by western blotting (Figure ). Inhibition of CDC25B should induce hyperphosphorylation of the CDK1 protein, resulting in the deactivation of CDK1 kinase and cell-cycle arrest.[73,74] In the vehicle control, CDK1 proteins were dephosphorylated, and no change occurred in the total amount of CDK1 proteins. In accordance with the results of the cell-cycle analysis and inhibitory activity for CDC25s in vitro, compound 3w inhibited the dephosphorylation of CDK1 (Figure ), whereas 3j and 3n did not inhibit the dephosphorylation of CDK1. These results indicated that 3w acted as a CDC25B inhibitor at the cellular level. However, compounds (3i and 3n) with small differences in the chemical structure have no markedly influence on the effect of inhibition of the dephosphorylation of the CDK1 protein.

Figure 4

Effect of compounds 3j, 3n, and 3w on CDK1 phosphorylation status.

Conclusions

In summary, we have developed an environmentally benign protocol for the synthesis of fluorinated 2-alkylthio-4-amino-quinazolines 3, under microwave irradiation conditions, using basic alumina as the solid support as well as a base catalyst. The protocol has a relatively broad isothiourea substrate scope and offers some significant advantages, such as improved energy efficiency, low cost, easy availability of the solid support, elimination of the use of any base or hazardous solvent, and applicability toward gram-scale synthesis. The biological activity of the 2-alkylthio-4-aminoquinazolines as CDC25B inhibitors was explored for the first time. Most target compounds exhibited excellent inhibitory activity against CDC25B as well as good antitumor activity. Thus, the fluorinated 2-alkylthio-4-aminoquinazoline series provides an attractive new combinatorial library of 4-aminoquinazolines for additional analysis and optimization.

Experimental Section

General Methods

All compounds were fully characterized by spectroscopic data. The NMR spectra were recorded on Bruker Ascend III 600 (1H: 600 MHz, 13C: 150 MHz) or Bruker DRX500 (1H: 500 MHz, 13C: 125 MHz). Chemical shifts (δ) are expressed in parts per million, and J values are given in hertz. Deuterated DMSO-d6 was used as the solvent. IR spectra were recorded on FT-IR Thermo Nicolet Avatar 360 using a KBr pellet. The reactions were monitored by thin layer chromatography (TLC) using silica gel GF254. The melting points were determined on a XT-4A melting point apparatus and are uncorrected. High-resolution mass spectrometry (HRMS) spectra were recorded on an Agilent LC/MSD TOF instrument. Column chromatography was performed on a silica gel (200–300 mesh). X-ray diffraction was obtained by APEX DUO. All microwave-assisted reactions were performed in a commercially available multimode microwave reactor (XH-100A, 100–1000 W, Beijing Xianhu Science and Technology Development Co. Ltd, Beijing, P. R. China). The temperature of the reaction mixture was measured by an immersed platinum resistance thermometer. Aluminum oxide (basic, FCP, 200–300 mesh) was purchased from Sinopharm Chemical Reagent Co., Ltd. (China).

Compounds 1 were purchased from TCI (Shanghai) Development Co., Ltd. Compounds 2 were prepared according to the literature.[57,58] All the other chemicals used in the experiment were purchased in analytical purity and were used without further purification.

General Procedure for the Synthesis of Compounds 3

A mixture of polyfluoro benzenedicarbonitriles 1 (1 mmol) and isothiouronium salts 2 (1.3 mmol) was dissolved in a minimum amount of 95% ethanol, which was then added to a round-bottomed flask, and basic alumina (2 g, FCP, 200–300 mesh) was added to it. The ethanol was evaporated to dryness under reduced pressure. The reaction mixture was subjected to irradiation in a microwave reactor (XH-100A Beijing XianHu Science, Beijing, China) at 80 or 120 °C (600 W) for the times reported in Tables and 3. The reaction was monitored by TLC. The crude products were directly purified by column chromatography using petroleum ether/ethyl acetate (4:1) to produce 3 with a yield of 62–93%. The products were further identified by Fourier transform infrared, NMR, and HRMS analyses.

2-(Butylthio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3a)

Light yellow solid: mp 206.5–208 °C; IR (KBr): 3432, 3184, 2961, 2929, 2860, 2244, 1648, 1585, 1541, 1516, 1468, 1441, 1398, 1295, 1272, 1007, 800, 658 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.71 (br, 1H, NH), 7.89 (br, 1H, NH), 3.15–3.12 (m, 2H, SCH2), 1.67–1.64 (m, 2H, CH2), 1.43–1.39 (m, 2H, CH2), 0.92–0.90 (m, 3H, CH3); 13C NMR (125 MHz, DMSO-d6): δ 174.4, 158.8 (d, J = 266.3 Hz), 158.0, 150.3 (d, J = 268.8 Hz), 146.2, 140.0 (d, J = 247.5 Hz), 110.1, 100.7, 86.5, 31.9, 30.6, 22.2, 14.3; 19F NMR (470 MHz, DMSO-d6): δ −103.8, −129.2, −155.4; HRMS (ESI): m/z calcd for C13H12F3N4S [M + H]+, 313.0729; found, 313.0720.

2-(Butylthio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3b)

Light yellow solid: mp 212.5–214 °C; IR (KBr): 3432, 3320, 3172, 2962, 2242, 1661, 1622, 1532, 1449, 1421, 1280, 981, 829, 658, 562 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.69 (br, 1H, NH), 7.91 (br, 1H, NH), 3.17–3.14 (m, 2H, SCH2), 1.70–1.64 (m, 2H, CH2), 1.43–1.39 (m, 2H, CH2), 0.91–0.88 (m, 3H, CH3); 13C NMR (125 MHz, DMSO-d6): δ 174.4, 161.5 (d, J = 267.5 Hz), 158.6 (d, J = 255.0 Hz), 158.3, 151.8, 111.6, 109.8, 100.5, 86.9, 31.7, 30.3, 22.0, 14.0; 19F NMR (470 MHz, DMSO-d6): δ −100.0, −103.3; HRMS (ESI): m/z calcd for C13H12N4ClF2S [M + H]+, 329.0434; found, 329.0433.

2-(Octylthio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3c)

White solid: mp 205–207 °C; IR (KBr): 3432, 3181, 2921, 2853, 2245, 1647, 1542, 1469, 1351, 1295, 1272, 1140, 1009, 877 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.71 (br, 1H, NH), 7.90 (br, 1H, NH), 3.14 (m, 2H, SCH2), 1.68 (m, 2H, CH2), 1.40 (m, 2H, CH2), 1.25 (m, 8H, 4CH2), 0.85 (m, 3H, CH3); 13C NMR (125 MHz, DMSO-d6): δ 173.9, 158.3 (d, J = 272.5 Hz), 157.6, 149.8 (d, J = 270.0 Hz), 145.8, 139.5 (d, J = 252.5 Hz), 109.6, 100.2, 86.0, 31.6, 30.4, 29.3, 28.9, 28.8, 28.6, 22.4, 14.3; HRMS (ESI): m/z calcd for C17H20F3N4S [M + H]+, 369.1355; found, 369.1362.

2-(Octylthio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3d)

White solid: mp 217–219 °C; IR (KBr): 3434, 3319, 3171, 2920, 2853, 2241, 1663, 1625, 1570, 1531, 1422, 1341, 1277, 981, 829 cm–1; 1H NMR (500 MHz, DMSO-d6 + CDCl3): δ 8.67 (br, 1H, NH), 7.81 (br, 1H, NH), 3.15 (m, 2H, SCH2), 1.71 (m, 2H, CH2), 1.41 (m, 2H, CH2), 1.24 (m, 8H, 4CH2), 0.85 (m, 3H, CH3); 13C NMR (125 MHz, DMSO-d6 + CDCl3): δ 175.1, 161.7 (d, J = 267.5 Hz), 158.9 (d, J = 263.8 Hz), 158.7, 152.3, 112.4, 109.8, 100.8, 87.1, 32.1, 31.2, 30.0, 29.5, 29.4, 29.3, 22.9, 14.7; HRMS (ESI): m/z calcd for C17H20N4ClF2S [M + H]+, 385.1060; found, 385.1052.

2-(Methylthio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3e)

Light yellow solid: mp 230–231 °C; IR (KBr): 3440, 3309, 3144, 2944, 2247, 1636, 1548, 1464, 1440, 1396, 1348, 1268, 1140, 1006, 940, 876 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.71 (br, 1H, NH), 7.91 (br, 1H, NH), 2.52 (s, 3H, CH3); 13C NMR (125 MHz, DMSO-d6): δ 174.7, 158.7 (d, J = 263.8 Hz), 158.0, 150.3 (d, J = 262.5 Hz), 146.2, 139.5 (d, J = 256.3 Hz), 110.1, 100.6, 86.6, 14.2; HRMS (ESI): m/z calcd for C10H6F3N4S [M + H]+, 271.0260; found, 271.0258.

2-(Methylthio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3f)

White solid: mp 231–233 °C; IR (KBr): 3437, 3316, 3174, 2244, 1652, 1626, 1564, 1539, 1426, 1341, 1275, 1127, 1091, 938, 828, 801 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.77 (br, 1H, NH), 7.97 (br, 1H, NH), 2.53 (s, 3H, CH3); 13C NMR (125 MHz, DMSO-d6): δ 174.6, 161.4 (d, J = 267.5 Hz), 158.5 (d, J = 255.0 Hz), 158.1, 151.6, 111.6, 109.6, 100.2, 86.7, 13.8; HRMS (ESI): m/z calcd for C10H6N4ClF2S [M + H]+, 286.9964; found, 286.9968.

2-((2-(2-Methoxyethoxy)ethyl)thio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3g)

White solid: mp 150–151 °C; IR (KBr): 3430, 3328, 3187, 2874, 2244, 1650, 1545, 1468, 1352, 1297, 1271, 1114, 1007, 943, 875 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.81 (br, 1H, NH), 7.80 (br, 1H, NH), 3.69–3.66 (m, 2H, OCH2), 3.58–3.44 (m, 4H, OCH2CH2O), 3.34–3.32 (m, 2H, SCH2), 3.25 (s, 3H, OCH3); 13C NMR (125 MHz, DMSO-d6): δ 173.4, 158.3 (d, J = 265.0 Hz), 157.7, 149.8 (d, J = 263.8 Hz), 145.7, 139.5 (d, J = 251.3 Hz), 109.6, 100.2, 86.2, 71.6, 69.6, 69.3, 58.4, 30.0; HRMS (ESI): m/z calcd for C14H14O2F3N4S [M + H]+, 359.0784; found, 359.0786.

2-((2-(2-Methoxyethoxy)ethyl)thio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3h)

White solid: mp 167–168 °C; IR (KBr): 3430, 3324, 3183, 2876, 2243, 1666, 1625, 1572, 1533, 1423, 1342, 1282, 1113, 981, 881 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.80 (br, 1H, NH), 7.98 (br, 1H, NH), 3.72–3.69 (m, 2H, OCH2), 3.58–3.57 (m, 2H, OCH2), 3.45–3.44 (m, 2H, CH2O), 3.36–3.34 (m, 2H, SCH2), 3.24 (s, 3H, OCH3); 13C NMR (125 MHz, DMSO-d6): δ 173.9, 161.3 (d, J = 266.3 Hz), 158.4 (d, J = 255.0 Hz), 158.2, 151.6, 111.5, 109.6, 100.4, 86.9, 71.6, 69.8, 69.3, 58.4, 30.2; HRMS (ESI): m/z calcd for C14H14O2N4ClF2S [M + H]+, 375.0489; found, 375.0493.

2-((2-Methoxyethyl)thio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3i)

Light yellow solid: mp 194.5–196 °C; IR (KBr): 3432, 3327, 3189, 2931, 2245, 1650, 1585, 1542, 1469, 1297, 1272, 1117, 800, 769, 658 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.61 (br, 1H, NH), 7.83 (br, 1H, NH), 3.59–3.56 (m, 2H, OCH2), 3.30–3.27 (m, 2H, SCH2), 3.26 (s, 3H, OCH3); 13C NMR (125 MHz, DMSO-d6): δ 173.4, 158.2 (d, J = 265.0 Hz), 157.6, 147.2 (d, J = 264.0 Hz), 145.5, 139.4 (d, J = 241.3 Hz), 109.5, 100.0, 86.2, 70.6, 58.2, 29.9; HRMS (ESI): m/z calcd for C12H10OF3N4S [M + H]+, 315.0522; found, 315.0516.

2-((2-Methoxyethyl)thio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3j)

Yellow solid: mp 207–208 °C; IR (KBr): 3432, 3322, 3186, 2926, 2242, 1664, 1624, 1570, 1533, 1421, 1341, 1279, 1116, 1050, 980 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.83 (br, 1H, NH), 8.00 (br, 1H, NH), 3.65–3.63 (m, 2H, OCH2), 3.38–3.36 (m, 2H, SCH2), 3.29 (s, 3H, OCH3); 13C NMR (125 MHz, DMSO-d6): δ 173.9, 161.4 (d, J = 267.5 Hz), 158.6 (d, J = 261.3 Hz), 158.3, 151.6, 111.6, 109.6, 100.4, 86.9, 70.8, 58.2, 30.0; HRMS (ESI): m/z calcd for C12H10ON4ClF2S [M + H]+, 331.0226; found, 331.0227.

2-(((Tetrahydrofuran-2-yl)methyl)thio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3k)

Light brown solid: mp 211–213 °C; IR (KBr): 3432, 3324, 3190, 2925, 2239, 1652, 1544, 1434, 1272, 1050, 1006, 893, 768, 558 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.82 (br, 1H, NH), 8.00 (br, 1H, NH), 4.10–4.07 (m, H, OCH), 3.81–3.64 (m, 2H, OCH2), 3.35 (m, 2H, SCH2), 2.01–1.61 (m, 4H, CH2CH2); 13C NMR (125 MHz, DMSO-d6): δ 173.6, 158.4 (d, J = 258.8 Hz), 157.7, 150.1 (d, J = 273.8 Hz), 145.8, 139.6 (d, J = 252.5 Hz), 109.1, 100.3, 86.2, 77.5, 67.9, 35.2, 30.7, 25.8; HRMS (ESI): m/z calcd for C14H12OF3N4S [M + H]+, 341.0678; found, 341.0683.

2-(((Tetrahydrofuran-2-yl)methyl)thio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3l)

Light yellow solid: mp 198–200 °C; IR (KBr): 3525, 3423, 3293, 3103, 2239, 1627, 1568, 1539, 1424, 1342, 1284, 1124, 1048, 973, 825 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.83 (br, 1H, NH), 8.00 (br, 1H, NH), 4.14–4.10 (m, H, OCH), 3.82–3.62 (m, 2H, OCH2), 3.40–3.32 (m, 2H, SCH2), 2.04–1.60 (m, 4H, CH2CH2); 13C NMR (125 MHz, DMSO-d6): δ 174.0, 161.4 (d, J = 261.3 Hz), 158.6 (d, J = 255.0 Hz), 158.2, 151.6, 111.6, 109.6, 100.4, 86.8, 77.5, 67.7, 35.2, 30.6, 25.7; HRMS (ESI): m/z calcd for C14H12ON4ClF2S [M + H]+, 357.0383; found, 357.0374.

2-(Allylthio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3m)

Light yellow solid: mp 215–217 °C; IR (KBr): 3431, 3184, 2244, 1665, 1648, 1542, 1467, 1295, 1008, 936, 563 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.82 (br, 1H, NH), 8.01 (br, 1H, NH), 5.97–5.96 (m, H, CH=C), 5.38–5.12 (m, 2H, C=CH2), 3.85–3.83 (m, 2H, SCH2); 13C NMR (125 MHz, DMSO-d6): δ 173.2, 158.4 (d, J = 265.0 Hz), 157.8, 149.9 (d, J = 270.0 Hz), 145.8, 139.6 (d, J = 236.3 Hz), 134.1, 118.6, 109.7, 100.3, 86.3, 33.4; HRMS (ESI): m/z calcd for C12H6N4F3S [M – H]−, 295.0271; found, 295.0272.

2-(Allylthio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3n)

Light yellow solid: mp 223–225.5 °C; IR (KBr): 3435, 3317, 3180, 2240, 1655, 1624b 1534, 1449, 1281, 980, 801, 558 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.81 (br, 1H, NH), 7.99 (br, 1H, NH), 6.04–5.96 (m, H, CH=C), 5.43–5.11 (m, 2H, C=CH2), 3.88–3.83 (m, 2H, SCH2); 13C NMR (125 MHz, DMSO-d6): δ 173.5, 161.4 (d, J = 267.5 Hz), 158.6 (d, J = 255.0 Hz) 158.3, 151.7, 134.2, 118.4, 111.6, 109.6, 100.4, 87.1, 33.3; HRMS (ESI): m/z calcd for C12H8ClF2N4S [M + H]+, 313.0121; found, 313.0123.

2-((Cyanomethyl)thio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3o)

Light yellow solid: mp 209.5–210.5 °C; IR (KBr): 3427, 3316, 3176, 2994, 2939, 2247, 1644, 1556, 1464, 1302, 1010, 800, 574 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.99 (br, 1H, NH), 8.17 (br, 1H, NH), 4.25 (m, 2H, SCH2CN); 13C NMR (125 MHz, DMSO-d6): δ 170.5, 158.4 (d, J = 262.5 Hz), 157.4, 150.3 (d, J = 263.8 Hz), 145.6, 139.7 (d, J = 252.5 Hz), 118.3, 109.6, 100.7, 87.2, 16.8; HRMS (ESI): m/z calcd for C11H4N5F3NaS [M + Na]+, 318.0032; found, 318.0031.

2-((Cyanomethyl)thio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3p)

Light yellow solid: mp 247–248.5 °C; IR (KBr): 3425, 3169, 2246, 1654, 1625, 1567, 1545, 1448, 1286, 829, 576 cm–1; 1H NMR (600 MHz, DMSO-d6): δ 9.03 (br, 1H, NH), 8.22 (br, 1H, NH), 4.27 (s, 2H, SCH2CN); 13C NMR (125 MHz, DMSO-d6): δ 170.9, 161.5 (d, J = 276.0 Hz), 158.9 (d, J = 262.5 Hz), 158.8, 151.7, 118.3, 112.1, 109.6, 100.9, 87.9, 16.9; HRMS (ESI): m/z calcd for C11H3N5ClF2S [M – H]−, 309.9771; found, 309.9771.

2-(Benzylthio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3q)

Light brown solid: mp 208–209 °C; IR (KBr): 3451, 3311, 3144, 2240, 1654, 1549, 1469, 1442, 1408, 1300, 1277, 1011, 799 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.86 (br, 1H, NH), 8.02 (br, 1H, NH), 7.49–7.47 (m, 2H, PhH), 7.32–7.29 (m, 2H, PhH), 7.25–7.23 (m, H, PhH), 4.42 (s, 2H, CH2); 13C NMR (125 MHz, DMSO-d6): δ 173.7, 158.8 (d, J = 266.3 Hz), 158.2, 150.4 (d, J = 267.5 Hz), 146.2, 140.1 (d, J = 250.0 Hz), 138.9, 129.9, 129.2, 127.9, 110.0, 100.8, 86.7, 35.1; HRMS (ESI): m/z calcd for C16H10N4F3S [M + H]+, 347.0573; found, 347.0576.

2-(Benzylthio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3r)

Light yellow solid: mp 247–248 °C; IR (KBr): 3448, 3314, 3137, 2240, 1655, 1329, 1566, 1537, 1425, 1340, 1280, 1126, 982 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.85 (br, 1H, NH), 8.02 (br, 1H, NH), 7.51–7.50 (m, 2H, PhH), 7.31–7.28 (m, 2H, PhH), 7.24–7.22 (m, H, PhH), 4.47 (s, 2H, CH2); 13C NMR (125 MHz, DMSO-d6): δ 173.6, 161.4 (d, J = 268.8 Hz), 158.6 (d, J = 263.8 Hz), 158.3, 151.7, 138.6, 129.5, 128.8, 127.4, 111.7, 109.4, 100.5, 86.99, 34.44; HRMS (ESI): m/z calcd for C16H10N4ClF2S [M + H]+, 363.0277; found, 363.0270.

2-((3,4-Dichlorobenzyl)thio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3s)

Light yellow solid: mp 268–269.5 °C; IR (KBr): 3455, 3178, 2238, 1645, 1548, 1468, 1301, 1277, 1012, 660, 610 cm–1; 1H NMR (600 MHz, DMSO-d6): δ 8.89 (br, 1H, NH), 8.07 (br, 1H, NH), 7.81 (s, H, PhH), 7.56–7.49 (m, 2H, PhH), 4.40 (s, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 172.8, 158.5 (d, J = 270.0 Hz), 157.9, 150.1 (d, J = 277.5 Hz), 145.7, 140.4, 139.7 (d, J = 250.5 Hz), 131.7, 131.1, 130.9, 130.1, 130.0, 109.65, 100.5, 86.4, 33.4; HRMS (ESI): m/z calcd for C16H6N4Cl2F3S [M – H]−, 412.9648; found, 412.9652.

2-((3,4-Dichlorobenzyl)thio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3t)

Light yellow solid: mp 267.5–268.5 °C; IR (KBr): 3452, 3317, 3144, 2241, 1648, 1548, 1299, 1276, 1011, 712 cm–1; 1H NMR (600 MHz, DMSO-d6): δ 8.91 (br, 1H, NH), 8.08 (br, 1H, NH), 7.85 (s, H, PhH), 7.56–7.53 (m, 2H, PhH), 4.44 (s, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 173.2, 161.5 (d, J = 259.5 Hz), 158.8 (d, J = 255.0 Hz), 158.5, 151.8, 140.6, 131.6, 131.2, 130.9, 130.1, 129.9, 111.7, 109.7, 100.7, 87.3, 33.3; HRMS (ESI): m/z calcd for C16H6N4Cl3F2S [M – H]−, 428.9352; found, 428.9354.

2-((3-Methoxybenzyl)thio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3u)

Light yellow solid: mp 181.5–182.5 °C; IR (KBr): 3450, 3178, 2240, 1655, 1628, 1538, 1283, 984, 800, 614 cm–1; 1H NMR (600 MHz, DMSO-d6): δ 8.87 (br, 1H, NH), 8.03 (br, 1H, NH), 7.23–7.21 (m, H, PhH), 7.08–7.04 (m, 2H, PhH), 6.81–6.80 (m, H, PhH), 4.41 (s, 2H, CH2), 3.73 (s, 3H, CH3); 13C NMR (150 MHz, DMSO-d6): δ 173.3, 160.0, 158.5 (d, J = 273.0 Hz), 157.8, 150.4 (d, J = 283.5 Hz), 145.8, 141.0, 139.9 (d, J = 277.5 Hz), 130.0, 121.7, 115.2, 113.1, 109.7, 100.5, 86.4, 55.4, 34.6; HRMS (ESI): m/z calcd for C17H11N4F3NaOS [M + Na]+, 399.0498; found, 399.0496.

2-((3-Methoxybenzyl)thio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3v)

Light yellow solid: mp 214–215.5 °C; IR (KBr): 3451, 3174, 2240, 1645, 1586, 1537, 1340, 1283, 983, 614 cm–1; 1H NMR (600 MHz, DMSO-d6): δ 8.89 (br, 1H, NH), 8.05 (br, 1H, NH), 7.23–7.20 (m, H, PhH), 7.11–7.06 (m, 2H, PhH), 6.81–6.79 (m, H, PhH), 4.46 (s, 2H, CH2), 3.72 (s, 3H, CH3); 13C NMR (150 MHz, DMSO-d6): δ 173.7, 161.5 (d, J = 262.5 Hz), 159.7, 158.8 (d, J = 271.5 Hz), 158.5, 151.8, 140.4, 129.9, 121.8, 115.0, 113.2, 111.7, 109.8, 100.7, 87.1, 55.5, 34.5; HRMS (ESI): m/z calcd for C17H11N4ClF2NaOS [M + Na]+, 415.0202; found, 415.0202.

2-((Naphthalen-2-ylmethyl)thio)-4-amino-6-carbonitrile-5,7,8-trifluoroquinazoline (3w)

Brown solid: mp 209–211 °C; IR (KBr): 3448, 3308, 3142, 2237, 1652, 1547, 1467, 1298, 1140, 1009, 743, 548 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.87 (br, 1H, NH), 8.03 (m, 2H, ArH), 7.86–7.84 (m, 2H, ArH), 7.83 (br, 1H, NH), 7.62–7.60 (m, H, ArH), 7.51–7.45 (m, 2H, ArH), 4.60 (s, 2H, CH2); 13C NMR (125 MHz, DMSO-d6): δ 173.1, 158.4 (d, J = 267.5 Hz), 157.8, 149.8 (d, J = 286.3 Hz), 145.8, 139.5 (d, J = 211.3 Hz), 136.0, 133.2, 132.5, 128.4, 128.2, 128.0, 127.9, 127.8, 126.7, 126.3, 109.7, 100.5, 86.3, 34.9; HRMS (ESI): m/z calcd for C20H12F3N4S [M + H]+, 397.0729; found, 397.0742.

2-((Naphthalen-2-ylmethyl)thio)-4-amino-6-carbonitrile-8-chloro-5,7-difluoroquinazoline (3x)

Light yellow solid: mp 249–250 °C; IR (KBr): 3448, 3313, 3181, 2240, 1653, 1627, 1565, 1538, 1427, 1341, 1280, 1125, 982, 827, 747 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.89 (br, 1H, NH), 8.08–8.03 (m, 2H, ArH), 7.85–7.83 (m, 2H, ArH), 7.82 (br, 1H, NH), 7.63–7.62 (m, H, ArH), 7.50–7.44 (m, 2H, ArH), 4.64 (s, 2H, CH2); 13C NMR (125 MHz, DMSO-d6): δ 173.6, 161.5 (d, J = 275.0 Hz), 158.7 (d, J = 261.3 Hz), 158.4, 151.8, 136.3, 133.2, 132.5, 128.4, 128.1, 128.0, 127.9, 127.8, 126.7, 126.3, 111.7, 109.8, 100.7, 87.1, 34.9; HRMS (FTMS cESI): m/z calcd for C20H12N4ClF2S [M + H]+, 413.0434; found, 413.0429.

2-(Butylthio)-4-amino-7-carbonitrile-5,6,8-trifluoroquinazoline (3y)

Light yellow solid: mp 176–177.5 °C; IR (KBr): 3439, 3314, 3180, 2959, 2244, 1652, 1537, 1278, 1005, 866 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.61 (br, 1H, NH), 7.75 (br, 1H, NH), 3.12–3.09 (m, 2H, SCH2), 1.69–1.63 (m, 2H, CH2), 1.46–1.38 (m, 2H, CH2), 0.94–0.91 (m, 3H, CH3); 13C NMR (125 MHz, DMSO-d6): δ 170.5, 157.7, 153.8 (d, J = 262.5 Hz), 142.6 (d, J = 253.8 Hz), 138.0.109.1, 107.1, 95.9, 31.4, 29.9, 21.8, 13.8; 19F NMR (470 MHz, DMSO-d6): δ −120.9, −139.2, −141.2; HRMS (ESI): m/z calcd for C13H12F3N4S [M + H]+, 313.0729; found, 313.0727.

2-((2-Methoxyethyl)thio)-4-amino-7-carbonitrile-5,6,8-trifluoroquinazoline (3z)

Light yellow solid: mp 176.5–178.5 °C; IR (KBr): 3519, 3299, 3180, 2950, 2248, 1625, 1534, 1281, 1085, 1001, 907, 474 cm–1; 1H NMR (600 MHz, DMSO-d6): δ 8.68 (br, 1H, NH), 7.81 (br, 1H, NH), 3.62–3.60 (m, 2H, OCH2), 3.34–3.33 (m, 2H, SCH2), 3.30 (s, 3H, OCH3); 13C NMR (150 MHz, DMSO-d6): δ 170.1, 158.0, 153.9 (d, J = 264.0 Hz), 142.7 (d, J = 262.5 Hz), 138.0, 109.2, 107.3, 96.0, 70.9, 58.3, 29.8; HRMS (ESI): m/z calcd for C12H10F3N4OS [M + H]+, 315.0522; found, 315.0522.

2-((2-(2-Methoxyethoxy)ethyl)thio)-4-amino-7-carbonitrile-5,6,8-trifluoroquinazoline (3a′)

Light yellow solid: mp 146–148 °C; IR (KBr): 3468, 3314, 3199, 2878, 2250, 1645, 1531, 1275, 1094, 1003, 925, 769, 652 cm–1; 1H NMR (600 MHz, DMSO-d6): δ 8.67 (br, 1H, NH), 7.82 (br, 1H, NH), 3.69–3.66 (m, 2H, OCH2), 3.58–3.43 (m, 4H, OCH2CH2O), 3.34–3.32 (m, 2H, SCH2), 3.25 (s, 3H, OCH3); 13C NMR (150 MHz, DMSO-d6): δ 170.1, 158.0, 153.9 (d, J = 262.5 Hz), 141.7 (d, J = 259.5 Hz), 138.1, 109.2, 107.3, 96.0, 71.7, 69.8, 69.5, 58.5, 29.9; HRMS (ESI): m/z calcd for C14H14F3N4O2S [M + H]+, 359.0784; found, 359.0785.

2-(Benzylthio)-4-amino-7-carbonitrile-5,6,8-trifluoroquinazoline (3b′)

Light yellow solid: mp 200–201 °C; IR (KBr): 3455, 3309, 3140, 2247, 1651, 1538, 1452, 1279, 1010, 798, 703 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.69 (br, 1H, NH), 7.82 (br, 1H, NH), 7.48–7.47 (m, 2H, PhH), 7.32–7.29 (m, 2H, PhH), 7.24–7.19 (m, H, PhH), 4.40 (s, 2H, CH2); 13C NMR (125 MHz, DMSO-d6): δ 169.9, 158.0, 154.0 (d, J = 261.3 Hz), 142.8 (d, J = 246.3 Hz), 138.7, 138.0, 129.6, 128.8, 127.5, 109.2, 107.3, 96.1, 34.5; HRMS (ESI): m/z calcd for C16H10F3N4S [M + H]+, 347.0573; found, 347.0576.

2-((Naphthalen-2-ylmethyl)thio)-4-amino-7-carbonitrile-5,6,8-trifluoroquinazoline (3c′)

Light yellow solid: mp 212–213.5 °C; IR (KBr): 3405, 3143, 2245, 1651, 1541, 1508, 1280, 1007, 864, 754, 473 cm–1; 1H NMR (500 MHz, DMSO-d6): δ 8.73 (br, 1H, NH), 8.00 (br, 1H, NH), 7.88–7.81 (m, 4H, ArH), 7.61–7.59 (m, H, ArH), 7.49–7.44 (m, 2H, ArH), 4.56 (s, 2H, CH2); 13C NMR (125 MHz, DMSO-d6): δ 169.7, 157.9, 153.8 (d, J = 263.8 Hz), 142.6 (d, J = 246.3 Hz), 137.8, 136.1, 133.1, 132.4, 128.3, 128.0, 127.8, 127.6, 126.6, 126.5, 126.2, 109.2, 107.2, 95.8, 31.5; HRMS (ESI): m/z calcd for C20H12F3N4S [M + H]+, 397.0729; found, 397.0728.