Catalyst- and Additive-Free Method for the Synthesis of 2-Substituted Benzothiazoles from Aromatic Amines, Aliphatic Amines, and Elemental Sulfur.

Under catalyst- and additive-free conditions, a novel, convenient, environmentally friendly method was developed for the synthesis of 2-substituted benzothiazoles via the three-component one pot reaction from aromatic amines, aliphatic amines, and elemental sulfur. The reaction achieves double C-S and one C-N bond formations via cleavage of two C-N bonds and multiple C-H bonds. Furthermore, the mechanism research shows that DMSO acts as an oxidant in the cyclization reaction.

Introduction

Benzothiazoles are highly important structural scaffolds for a variety of compounds that prevalently exist in functional molecules applied in biology, pharmacy, and material science.[1] As one of the most important components, 2-substituted benzothiazoles exhibit good pharmaceutical activity, which appear as a core skeleton in antimicrobial, antitumor, anticonvulsant, antituberculosis, calcium-channel antagonist, and neuroprotective agents.[2] Therefore, considerable interest has been inclined toward the development of efficient methods for the synthesis of 2-substituted benzothiazoles.[3]

Traditional methods for synthesizing 2-subsituted benzothiazoles involve two kinds of approaches. The first one is transition-metal-catalyzed intramolecular cyclization of thiobenzanilides.[4] The second kind of methods involve the condensation of 2-aminobenzenethiol with alcohols, carboxylic acids, aldehydes, aryl ketones, arylacetylenes, or styrenes.[5] In addition, the C–H functionalization of the 2-position of benzothiazoles with aryl halides, arylsilanes, aromatic carboxylic acids, arylboronic acids, and triflates has become a useful strategy for the construction of 2-arylbenzothiazoles.[6] However, these approaches still have some shortcomings, such as employing prefunctionalized substrates, stoichiometric toxic oxidants, expensive transition-metal catalysts, etc. Recently, the methods of synthesizing 2-substituted benzothiazoles by three-component reaction are very popular.[7] The advantages of the three-component reaction involve a simple operation and using cheap and easily available elemental sulfur as the sulfur source. Among them, the classic methods for the synthesis of 2-substituted benzothiazoles mainly include the transition metal-catalyzed intramolecular cyclization of 2-haloanilides[8] and condensation of o-halonitrobenzenes[9] with other reagents under metal-free conditions. These methods are very effective for the construction of 2-substituted benzothiazoles. However, these reactions are still limited by the use of transition-metal catalysts and halogenated substrates. Therefore, it is highly desirable to exploit the novel strategies to synthesize 2-substituted benzothiazoles from readily available raw materials under mild and simple reaction conditions. Amines are one of the most useful synthons in organic synthesis that widely exist in nature with stable chemical properties and are commercially available. It would be a very good strategy to overcome these deficiencies by using amine compounds instead of halogenated compounds as reaction substrates. Recently, Deng and co-workers reported some novel methods of synthesizing 2-substituted benzothiazoles from amines, elemental sulfur, and benzaldehydes[10] (Scheme a) or styrenes[11] (Scheme b). In addition, Chen and co-workers developed an iodine-catalyzed one-pot reaction of aromatic amines, acetophenones, and sulfur powder for the synthesis of 2-aryl benzothiazoles[12] (Scheme c). In order to have the prospect of industrialization, it is still urgent to find simpler and more economical ways to synthesize 2-substituted benzothiazoles.

Scheme 1

Synthesis of 2-Substituted Benzothiazoles from Amine and Elemental Sulfur under Metal-Free Conditions

Within our continuous program on the development of a new approach for the construction of 2-substituted benzothiazoles by using sulfide or sulfur powder as a sulfur source,[13] we herein report a three-component reaction for the construction of 2-substituted benzothiazoles from aromatic amines, aliphatic amines, and elemental sulfur under catalyst-free and additive-free conditions.

Results and Discussion

We began our study by examining the reaction of 2-naphthylamine (1a), benzylamine (2a), and sulfur powder in DMSO at 140 °C under a nitrogen atmosphere (Table ). To our delight, the desired product 3a was obtained in an 83% yield (entry 1). Then, the solvents including DMF, NMP, MeCN, and DMAC were screened (entries 2–5). The results indicated that the best solvent for this reaction was DMSO. Subsequently, the amount of S8 and 2a was evaluated (entries 6–10). The results showed that 2 equiv of 2a and 3 equiv of S8 are the most suitable doses, giving the corresponding product in a 90% yield (entry 8). Finally, the temperature screening indicated that lower temperature is not suitable for this reaction and 140 °C is the most suitable temperature (entries 8 and 11). Thus, the optimal condition of this three-component reaction is as follows: 1a (0.2 mmol), 2a (0.4 mmol), and S8 (0.075 mmol) in DMSO (2 mL) under N2 at 140 °C for 22 h.

Table 1

Optimization of the Reaction Conditionsa

entry	S (equiv)	solvent	yield (%)b
1	3	DMSO	83
2	3	DMF	14
3	3	NMP	38
4	3	CH3CN	27
5	3	DMAC	28
6	4	DMSO	63
7	2	DMSO	64
8c	3	DMSO	90
9d	3	DMSO	65
10e	3	DMSO	87
11f	3	DMSO	64

Reaction conditions: 1a (0.2 mmol), 2a (0.3 mmol), and solvent (2 mL) under a N2 atmosphere in a sealed Schlenk tube at 140 °C for 22 h.

Isolated yields.

2a (2 equiv).

2a (1.2 equiv)

2a (3 equiv).

120 °C.

With the optimized reaction conditions in hand, we evaluated the scope and generality of this three-component reaction. Initially, the various monosubstituted benzylamines were screened (Table ). The results demonstrated that both the electron-rich and electron-deficient group-substituted benzylamines could smoothly be transformed into the desired products. Meanwhile, substituents at different positions of the benzyl (para, meta, and ortho positions) could all achieve moderate to good yields, and the steric hindrance effect is not obvious (3a–3u). To our delight, the substrate bearing active amino at para, meta, and ortho positions of the benzyl formed 3g, 3m, and 3r in 70, 73, and 42 yields, respectively. As expected, multisubstituted benzylamines could also efficiently be converted into the corresponding products in medium to good yields (3v–3z). The results showed that the electron-donating-group substrates displayed higher reactivity than that of the electron-withdrawing-group substrates. Notably, the reaction was compatible with some heterocyclic amines such as pyridinylmethanamines and thiophen-2-ylmethanamine, affording the corresponding products 3aa–3ad in 80, 61, 32, 62, and 16% yields, respectively. Moreover, naphthalen-1-amine could be successfully converted into polycyclic product 3ae in an 80% yield. Finally, the substrate 6-bromonaphthalen-2-amine provided 7-bromo-2-phenylnaphtho[2,1-d]thiazole 3ba in a 76% yield.

Table 2

Substrate Scope with Respect to Benzylaminesa,b

1 (0.2 mmol), 2 (0.4 mmol), S8 (0.075 mmol), and DMS0 (2 mL) under a N2 atmosphere in a sealed Schlenk tube at 140 °C for 22 h.

Isolated yields.

To further examine the scope and limitations of the reaction, various anilines were tested instead of naphthalenamines (Table ). However, only electron-donating groups such as methyl, methoxyl, phenoxy, N,N-dimethylamino, and acetyl amino-substituted anilines could smoothly be transformed into the target products in moderate to good yields (4a–4i). These results indicated that the reaction might undergo a process of an electrophilic attack.

Table 3

Substrate Scope of Anilinesab

1(0.2 mmol), 2a (0.4 mmol), S8 (0.075 mmol), and DMS0 (2 mL) under a N2 atmosphere in a sealed Schlenk tube at 140 °C for 22 h,

Isolated yields.

To further expand the substrate scope, we next examined the effects of the different substitutes of some other aliphatic amines (Table ). Various secondary amides (2af–2ai) and tertiary amines (2aj–2ak) were successfully converted into the corresponding product 3a in 60–99% yields under the standard reaction conditions. These results indicated that the substituents from N-substituted benzylamine did not remarkably affect the reaction. To our delight, the aliphatic amine such as triethylamine and isobutylamine afforded the desired products (3ak and 3al) in 28 and 19% yields, respectively. However, we also tried some other alkyl-substituted substrates such as diethylamine (2am) or phenylethylamine (2an); the reaction did not get the target product under the standard conditions.

Table 4

Substrate Scope of Benzylamines and Aliphatic Aminesab

1a (0.2 mmol), 2 (2.0 equiv), S8 (0.075 mmol), and DMSO (2 mL) under a N2 atmosphere in a sealed Schlenk tube at 140 °C for 22 h.

Isolated yields.

A series of control experiments were performed to investigate the possible reaction mechanism (Scheme ). First, in order to capture the reaction intermediate, under the standard reaction conditions, when the reaction of 2-naphthylamine (1a), benzylamine (2a), and sulfur powder was performed in 2 h, the imine (A and D), benzaldehyde (B), N-benzylthiobenzamide (C), and benzonitrile (E) could be detected from the reaction mixture by GC–MS analysis (Scheme a). Subsequently, under standard reaction conditions, C or E could not transfer into 2-phenylnaphtho[2,1-d]thiazole (Scheme b,c). However, the reaction of A or B with 2-naphthylamine and sulfur powder generated the desired product 3a in 97 or 69% yields, respectively, which indicated that this reaction probably involves two different pathways (Scheme d,e). In addition, the reaction of D and sulfur powder could smoothly transform into the target product 3a (Scheme f). The result indicated that A, B, and D may be the intermediates of the reaction. In addition, in the absence of 2-naphthylamine under same reaction conditions, the intermediates A and B were detected from the reaction mixture by GC–MS analysis (Scheme g). Furthermore, when DMSO was replaced by methyl phenyl sulfoxide, benzothiazolethione 2a could be isolated in a 65% yield, and the methyl(phenyl)sulfide was detected via GC–MS analysis (Scheme h). These results reveal that DMSO could be performed as an oxidant in this reaction. When elemental sulfur was removed from the reaction, the reaction could not proceed (Scheme i). In addition, the corresponding product 3a could be obtained under the conditions of DMF, NMP, CH3CN, or DMAC instead of DMSO (Table , entry 2–5). These results indicated that the sulfur source of the product came from S8. Finally, in order to study the practicability of the reaction, we performed a 5 mmol-scale magnification experiment and obtained the desired product in an 80% yield (Scheme j).

Scheme 2

Controlled Experiments

Base on the experimental results and previous reports,[13c,14] a possible reaction mechanism has been outlined (Scheme ). First, under the oxidation of DMSO, benzylamine 2a is converted into imine intermediate A, which may undergo two reaction pathways to form the intermediate D. In route a, D is formed by a nucleophilic addition/elimination reaction of 2-naphthylamine 1a with A. In route b, A is converted to intermediate B by hydrolysis, and then B reacts with 2-naphthylamine to generate D. Subsequently, an electrophilic attack of elemental sulfur (S) to D gives F, which releases elemental sulfur (S) and a hydrogen proton to obtain sulfurated imine G. Finally, intermolecular nucleophilic cyclization of intermediate G generates thiazoline H and then proceeds through oxidative aromatization to give the desired product 2-phenylnaphtho[2,1-d]thiazole 3a.

Scheme 3

Possible Mechanism

Conclusions

In summary, we have disclosed a novel, convenient, environmentally friendly method for synthesis of 2-substituted benzothiazoles and 2-substituted naphthothiazoles from aromatic amines, aliphatic amines, and sulfur powder under catalyst- and additive-free conditions. In this reaction, DMSO served as an oxidant and solvent. This transformation is easy to conduct under mild oxidative conditions to generate double C–S and one C–N bond formations in a cascade sequence and features a broad substrate scope, good functional group tolerance, and an environmentally benign character. Further studies of this method will focus on the detailed mechanism and applications in organic synthesis.

Experimental Section

General Information

1H, 13C, and 19F NMR spectra were recorded on a Bruker Avance-500 instrument (500 MHz for 1H, 125 MHz for 13C, and 125 MHz for 19F) at room temperature, unless otherwise noted. High-resolution mass spectra (HRMS) were recorded on a Thermo Scientific LTQ Orbitrap XL mass spectrometer using ESI (electrospray ionization). Low-resolution mass spectra (LRMS) data were measured on GCMS-QP2010 Ultra. Reactions were monitored by thin-layer chromatography. Column chromatography was performed on silica gel (200–300 mesh) using petroleum ether (PE)/ethyl acetate (EA). Analytical-grade solvents and commercially available reagents were purchased from commercial sources and used directly without further purification unless otherwise stated.

Typical Experimental Procedure for the Synthesis of 3 or 4

The sealed Schlenk tube was charged with 2-naphthylamines or anilines (1, 0.2 mmol), aliphatic amines (2, 0.4 mmol), S8 (0.075 mmol), and DMSO (2 mL). Then, under the protection of a nitrogen atmosphere, the mixture was stirred at 140 °C for 22 h. After the completion of the reaction (monitored by TLC), the reaction mixture was cooled to room temperature, quenched by water, and extracted with ethyl acetate. The combined organic layer was dried over Na2SO4 and concentrated in vacuum, and the resulting residue was purified by silica gel column chromatography (petroleum ether/ethyl acetate) to afford the pure product 3 or 4.

Typical Experimental Procedure for the Scale Magnification Experiments

The sealed Schlenk tube was charged with 2-naphthylamine 1a (5 mmol, 0.7180 g), benzylamine 2a (10 mmol, 1.0720), S8 (1.875 mmol, 0.4865 g), and DMSO (10 mL). Then, under the protection of a nitrogen atmosphere, the mixture was stirred at 140 °C for 22 h. After the completion of the reaction (monitored by TLC), the reaction mixture was cooled to room temperature, quenched by water, and extracted with ethyl acetate. The combined organic layer was dried over Na2SO4 and concentrated in vacuum, and the resulting residue was purified by silica gel column chromatography (petroleum ether/ethyl acetate) to afford the pure product (3a) in 80% yields.

2-Phenylnaphtho[2,1-d]thiazole (3a)[13]

Prepared according to the typical procedure as a light yellow solid (48 mg, 90%). mp: 109–110 °C. 1H NMR (CDCl3, 500 MHz) δ 8.15–8.13 (m, 2H), 8.11 (d, J = 8.5 Hz, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 9.0 Hz, 1H), 7.58 (t, J = 7.0 Hz, 1H), 7.55–7.49 (m, 4H). 13C NMR (CDCl3, 125 MHz) δ 167.08, 152.11, 133.57, 132.11, 130.94, 130.65, 128.98, 128.89, 127.97, 127.35, 127.23, 126.92, 125.91, 125.08, 121.61.

2-(p-Tolyl)naphtho[2,1-d]thiazole (3b)[13]

Prepared according to the typical procedure as a yellow solid (44 mg, 79%). mp: 137–139 °C. 1H NMR (CDCl3, 500 MHz) δ 8.09 (d, J = 9.0 Hz, 1H), 8.04–8.00 (m, 3H), 7.95 (d, J = 8.0 Hz, 1H), 7.86 (d, J = 9.0 Hz, 1H), 7.59 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.53 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.30 (d, J = 8.0 Hz, 2H), 2.43 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 167.35, 152.19, 141.09, 131.93, 131.00, 130.95, 129.70, 128.92, 128.07, 127.28, 127.20, 126.91, 125.81, 125.10, 121.60, 21.47.

2-(4-(tert-Butyl)phenyl)naphtho[2,1-d]thiazole (3c)[10]

Prepared according to the typical procedure as a yellow solid (65 mg, 95%). mp: 120–122 °C. 1H NMR (CDCl3, 500 MHz) δ 8.11 (d, J = 9.0 Hz, 1H), 8.08 (d, J = 8.5 Hz, 2H), 8.03 (d, J = 8.0 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 8.5 Hz, 1H), 7.60 (t, J = 7.0 Hz, 1H), 7.55–7.52 (m, 3H), 1.39 (s, 9H). 13C NMR (CDCl3, 125 MHz) δ 167.26, 154.25, 152.24, 131.97, 130.97, 128.94, 128.09, 127.28, 127.10, 126.92, 126.00, 125.84, 125.13, 121.65, 34.94, 31.17.

2-(4-(Trifluoromethoxy)phenyl)naphtho[2,1-d]thiazole (3d)[13]

Prepared according to the typical procedure as a yellow solid (67 mg, 95%). mp: 141–143 °C. 1H NMR (CDCl3, 500 MHz) δ 8.16–8.14 (m, 2H), 8.08 (d, J = 7.5 Hz, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 8.5 Hz, 1H), 7.61–7.58 (m, 1H), 7.56–7.54 (m, 1H), 7.34 (d, J = 8.5 Hz, 2H). 13C NMR (CDCl3, 125 MHz) δ 165.26, 152.20, 150.83, 132.38, 132.26, 131.13, 129.01, 128.79, 128.00, 127.64, 127.12, 126.18, 125.14, 121.67, 121.25, 120.40 (q, J = 256.50). 19F NMR (CDCl3, 470 MHz) δ −57.63.

2-(4-Methoxyphenyl)naphtho[2,1-d]thiazole (3e)[13]

Prepared according to the typical procedure as a yellow solid (39 mg, 65%). mp: 106–108 °C. 1H NMR (CDCl3, 500 MHz) δ 8.08–8.06 (m, 3H), 7.99 (d, J = 8.0 Hz, 1H), 7.94 (d, J = 8.0 Hz, 1H), 7.85 (d, J = 9.0 Hz, 1H), 7.58 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.52 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.00 (d, J = 8.5 Hz, 2H), 2.87 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 167.05, 161.72, 152.16, 131.68, 130.87, 128.92, 128.83, 128.07, 127.24, 126.89, 126.47, 125.71, 125.04, 121.47, 114.37, 55.40.

2-(4-Isopropylphenyl)naphtho[2,1-d]thiazole (3f)

Prepared according to the typical procedure as an orange-yellow solid (36 mg, 61%). mp: 95–97 °C. 1H NMR (CDCl3, 500 MHz) δ 8.11 (d, J = 9.0 Hz, 1H), 8.08 (d, J = 8.0 Hz, 2H), 8.02 (d, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 9.0 Hz, 1H), 7.59 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.53 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.37 (d, J = 8.0 Hz, 2H), 3.02–2.97 (m, 1H), 1.32 (d, J = 6.5 Hz, 6H). 13C NMR (CDCl3, 125 MHz) δ 167.31, 152.20, 151.95, 131.93, 131.33, 130.92, 128.91, 128.05, 127.33, 127.25, 127.11, 126.89, 125.80, 125.09, 121.61, 34.08, 23.75. HRMS (ESI) m/z calcd for C20H18NS+ (M + H)+: 304.1155, found: 304.1154.

4-(Naphtho[2,1-d]thiazol-2-yl)aniline (3g)

Prepared according to the typical procedure as a brown solid (38 mg, 70%). mp: 198–200 °C. 1H NMR (CDCl3, 500 MHz) δ 8.05 (d, J = 8.5 Hz, 1H), 8.00 (d, J = 8.0 Hz, 1H), 7.96–7.94 (m, 3H), 7.85 (d, J = 9.0 Hz, 1H), 7.58 (t, J = 7.5 Hz, 1H), 7.51 (t, J = 7.5 Hz, 1H), 6.75 (d, J = 8.5 Hz, 2H), 4.00 (s, 2H). 13C NMR (CDCl3, 125 MHz) δ 167.81, 152.25, 149.02, 131.27, 130.78, 128.92, 128.88, 128.13, 127.08, 126.82, 125.51, 125.04, 124.09, 121.40, 114.84. HRMS (ESI) m/z calcd for C17H13N2S+ (M + H)+: 277.0794, found: 277.0792.

2-(4-Fluorophenyl)naphtho[2,1-d]thiazole (3h)

Prepared according to the typical procedure as a yellow solid (35 mg, 62%). mp: 139–142 °C. 1H NMR (CDCl3, 500 MHz) δ 8.13–8.10 (m, 2H), 8.08 (d, J = 9.0 Hz, 1H), 8.00 (d, J = 8.0 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 8.5 Hz, 1H), 7.61–7.58 (m, 1H), 7.54 (t, J = 7.5 Hz, 1H), 7.19 (t, J = 8.5 Hz, 2H). 13C NMR (CDCl3, 125 MHz) δ 165.83, 164.28 (d, J = 250.1 Hz), 152.15, 132.15, 131.04, 130.01 (d, J = 3.3 Hz), 129.23 (d, J = 8.8 Hz), 128.98, 128.02, 127.50, 127.05, 126.02, 125.09, 121.59, 116.16 (d, J = 21.9 Hz). 19F NMR (CDCl3, 470 MHz) δ −109.22. HRMS (ESI) m/z calcd for C17H11FNS+ (M + H)+: 280.0591, found: 280.0593.

2-(4-Chlorophenyl)naphtho[2,1-d]thiazole (3i)[10]

Prepared according to the typical procedure as a yellow solid (37 mg, 63%). mp: 181–183 °C. 1H NMR (CDCl3, 500 MHz) δ 8.08–8.04 (m, 3H), 8.00 (d, J = 8.0 Hz, 1H), 7.96 (d, J = 7.5 Hz, 1H), 7.87 (d, J = 9.0 Hz, 1H), 7.62–7.59 (m, 1H), 7.57–7.54 (m, 1H), 7.47 (d, J = 9.0 Hz, 2H). 13C NMR (CDCl3, 125 MHz) δ 165.67, 152.12, 136.70, 132.23, 132.11, 131.06, 129.26, 128.98, 128.41, 127.96, 127.59, 127.09, 126.12, 125.11, 121.59.

2-(4-Bromophenyl)naphtho[2,1-d]thiazole (3j)[10]

Prepared according to the typical procedure as a yellow solid (32 mg, 47%). mp: 197–199 °C. 1H NMR (CDCl3, 500 MHz) δ 8.08 (d, J = 8.5 Hz, 1H), 8.03–7.99 (m, 3H), 7.97 (d, J = 8.0 Hz, 1H), 7.88 (d, J = 9.0 Hz, 1H), 7.65–7.63 (m, 2H), 7.61–7.59 (m, 1H), 7.56 (td, J = 8.0 Hz, J = 1.5 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 165.77, 152.22, 132.63, 132.26, 131.14, 129.03, 128.66, 128.03, 127.64, 127.13, 126.17, 125.16, 125.12, 121.66.

2-(4-(Trifluoromethyl)phenyl)naphtho[2,1-d]thiazole (3k)[13]

Prepared according to the typical procedure as a yellow solid (45 mg, 67%). mp: 173–175 °C. 1H NMR (CDCl3, 500 MHz) δ 8.16 (d, J = 8.0 Hz, 2H), 8.06 (d, J = 9.0 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.92 (d, J = 8.0 Hz, 1H), 7.84 (d, J = 9.0 Hz, 1H), 7.71 (d, J = 8.5 Hz, 2H), 7.59–7.52 (m, 2H). 13C NMR (CDCl3, 125 MHz) δ 164.91, 152.16, 136.71, 132.58, 132.08 (q, J = 32.63 Hz), 131.17, 128.98, 127.89, 127.74, 127.37, 127.14, 126.31, 125.94 (q, J = 3.88 Hz), 125.11, 122.22 (q, J = 270.75 Hz), 121.70. 19F NMR (CDCl3, 470 MHz) δ −62.78.

2-(m-Tolyl)naphtho[2,1-d]thiazole (3l)[13]

Prepared according to the typical procedure as a yellow solid (45 mg, 79%). mp: 102–104 °C. 1H NMR (CDCl3, 500 MHz) δ 8.11 (d, J = 8.5 Hz, 1H), 8.03–7.99 (m, 2H), 7.96 (d, J = 8.0 Hz, 1H), 7.92 (d, J = 7.5 Hz, 1H), 7.87 (d, J = 9.0 Hz, 1H), 7.59 (td, J = 7.0 Hz, J = 1.5 Hz, 1H), 7.54 (td, J = 8.0 Hz, J = 1.5 Hz, 1H), 7.40 (t, J = 8.0 Hz, 1H), 7.30 (d, J = 7.5 Hz, 1H), 2.47 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 167.42, 152.16, 138.86, 133.56, 132.10, 131.54, 131.00, 128.94, 128.93, 128.07, 127.75, 127.35, 126.96, 125.91, 125.12, 124.59, 121.65, 21.35.

3-(Naphtho[2,1-d]thiazol-2-yl)aniline (3m)

Prepared according to the typical procedure as a yellow solid (41 mg, 73%). mp: 182–185 °C. 1H NMR (CDCl3, 500 MHz) δ 8.09 (d, J = 9.0 Hz, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.86 (d, J = 9.0 Hz, 1H), 7.59 (t, J = 7.5 Hz, 1H), 7.55–7.48 (m, 3H), 7.28 (t, J = 8.0 Hz, 1H), 6.80 (dd, J = 7.5 Hz, J = 1.5 Hz, 1H), 3.68 (s, 2H). 13C NMR (CDCl3, 125 MHz) δ 167.50, 152.04, 147.00, 134.52, 132.08, 130.96, 129.96, 128.92, 128.03, 127.31, 126.94, 125.89, 125.10, 121.61, 117.82, 117.40, 113.14. HRMS (ESI) m/z calcd for C17H13N2S+ (M + H)+: 277.0794, found: 277.0792.

2-(3-Fluorophenyl)naphtho[2,1-d]thiazole (3n)[10]

Prepared according to the typical procedure as a yellow solid (45 mg, 81%). mp: 113–115 °C. 1H NMR (CDCl3, 500 MHz) δ 8.08 (d, J = 9.0 Hz, 1H), 8.00 (d, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.88–7.85 (m, 3H), 7.60 (t, J = 7.5 Hz, 1H), 7.55 (t, J = 7.0 Hz, 1H), 7.48–7.44 (m, 1H), 7.18 (td, J = 8.0 Hz, J = 2.0 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 165.44 (d, J = 3.00 Hz), 163.06 (d, J = 245.8 Hz), 152.10, 135.73 (d, J = 8.00 Hz), 132.37, 131.14, 130.60 (d, J = 8.1 Hz), 128.98, 127.98, 127.61, 127.09, 126.18, 125.13, 123.02 (d, J = 3.1 Hz), 121.70, 117.51 (d, J = 21.50 Hz), 114.03 (d, J = 23.5 Hz). 19F NMR (CDCl3, 470 MHz) δ −111.96.

2-(2-Bromophenyl)naphtho[2,1-d]thiazole (3o)[10]

Prepared according to the typical procedure as a yellow solid (52 mg, 75%). mp: 148–150 °C. 1H NMR (CDCl3, 500 MHz) δ 8.27 (t, J = 2.0 Hz, 1H), 8.05 (d, J = 8.5 Hz, 1H), 7.98–7.92 (m, 3H), 7.84 (d, J = 8.5 Hz, 1H), 7.58–7.51 (m, 3H), 7.32 (t, J = 8.0 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 165.03, 152.01, 135.42, 133.39, 132.32, 131.07, 130.41, 129.90, 128.92, 127.88, 127.59, 127.04, 126.14, 125.77, 125.07, 123.14, 121.60.

2-(3-(Trifluoromethyl)phenyl)naphtho[2,1-d]thiazole (3p)

Prepared according to the typical procedure as a white solid (51 mg, 76%). mp: 133–135 °C. 1H NMR (CDCl3, 500 MHz) δ 8.41 (s, 1H), 8.26 (d, J = 7.5 Hz, 1H), 8.09 (d, J = 8.5 Hz, 1H), 8.01 (d, J = 8.5 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.88 (d, J = 9.0 Hz, 1H), 7.73 (d, J = 8.0 Hz, 1H), 7.63–7.59 (m, 2H), 7.56 (td, J = 8.0 Hz, J = 1.0 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 165.07, 152.09, 134.38, 132.42, 131.60 (q, J = 32.6 Hz), 131.19, 130.35, 129.58, 129.01, 127.94, 127.77, 127.18, 127.05 (q, J = 3.8 Hz), 126.31, 125.13, 123.96 (q, J = 4.00 Hz), 123.77 (q, J = 270.88 Hz), 121.67. 19F NMR (CDCl3, 470 MHz) δ −62.70. HRMS (ESI) m/z calcd for C18H11F3NS+ (M + H)+: 330.0559, found: 330.0557.

2-(o-Tolyl)naphtho[2,1-d]thiazole (3q)[13]

Prepared according to the typical procedure as a white solid (49 mg, 87%). mp: 69–71 °C. 1H NMR (CDCl3, 500 MHz) δ 8.15 (d, J = 9.0 Hz, 1H), 8.06 (d, J = 8.0 Hz, 1H), 7.99 (d, J = 8.0 Hz, 1H), 7.90 (d, J = 9.0 Hz, 1H), 7.87 (d, J = 8.0 Hz, 1H), 7.61 (td, J = 7.0 Hz, J = 1.5 Hz, 1H), 7.56 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.42–7.33 (m, 3H), 2.73 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 166.96, 151.77, 137.12, 133.08, 132.72, 131.55, 130.96, 130.51, 129.87, 128.94, 127.98, 127.19, 126.94, 126.13, 125.95, 125.26, 121.84, 21.48.

2-(Naphtho[2,1-d]thiazol-2-yl)aniline (3r)

Prepared according to the typical procedure as a yellow solid (24 mg, 42%). mp: 134–136 °C. 1H NMR (CDCl3, 500 MHz) δ 8.02–8.00 (m, 2H), 7.95 (d, J = 8.0 Hz, 1H), 7.84 (d, J = 9.0 Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H), 7.59 (t, J = 7.0 Hz, 1H), 7.53 (t, J = 7.5 Hz, 1H), 7.24 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 6.82–6.77 (m, 2H), 6.40 (s, 2H). 13C NMR (CDCl3, 125 MHz) δ 168.43, 151.59, 146.46, 131.30, 130.86, 130.08, 130.03, 128.89, 127.79, 127.05, 126.91, 125.72, 125.25, 121.18, 116.96, 116.82, 115.40. HRMS (ESI) m/z calcd for C17H13N2S+ (M + H)+: 277.0794, found: 277.0795.

2-(2-Fluorophenyl)naphtho[2,1-d]thiazole (3s)[13]

Prepared according to the typical procedure as a yellow solid (47 mg, 84%). mp: 155–157 °C. 1H NMR (CDCl3, 500 MHz) δ 8.46 (td, J = 7.5 Hz, J = 1.5 Hz, 1H), 8.11 (d, J = 9.0 Hz, 1H), 8.07 (d, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 9.0 Hz, 1H), 7.59 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.54 (td, J = 8.5 Hz, J = 1.5 Hz, 1H), 7.47–7.42 (m, 1H), 7.31 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.24–7.22 (m, 1H). 13C NMR (CDCl3, 125 MHz) δ 160.58 (d, J = 196.38 Hz), 159.60 (d, J = 61.25 Hz), 150.71, 133.03 (d, J = 8.13 Hz), 131.84 (d, J = 8.53 Hz), 131.05, 129.43 (d, J = 2.13 Hz), 128.96, 128.01, 127.48, 127.02, 126.13, 125.09, 124.72 (d, J = 3.38 Hz), 121.63, 121.48 (d, J = 10.88 Hz), 116.35 (d, J = 21.75). 19F NMR (CDCl3, 470 MHz) δ −111.91.

2-(2-Chlorophenyl)naphtho[2,1-d]thiazole (3t)[10]

Prepared according to the typical procedure as a white solid (48 mg, 81%). mp: 143–146 °C. 1H NMR (CDCl3, 500 MHz) δ 8.34 (d, J = 7.5 Hz ,1H), 8.14 (d, J = 9.0 Hz, 1H), 8.10 (d, J = 8.0 Hz, 1H), 7.97 (d, J = 8.0 Hz, 1H), 7.89 (d, J = 9.0 Hz, 1H), 7.61 (t, J = 7.0 Hz, 1H), 7.56 (t, J = 7.0 Hz, 2H), 7.45–7.39 (m, 2H). 13C NMR (CDCl3, 125 MHz) δ 162.79, 150.58, 133.40, 132.44, 132.15, 131.53, 131.08, 130.90, 130.80, 128.94, 127.92, 127.42, 127.12, 127.00, 126.15, 125.10, 121.70.

2-(2-Bromophenyl)naphtho[2,1-d]thiazole (3u)[10]

Prepared according to the typical procedure as a white solid (46 mg, 67%). mp: 136–139 °C. 1H NMR (CDCl3, 500 MHz) δ 8.15–8.12 (m, 2H), 8.08 (d, J = 8.0 Hz, 1H), 7.98 (d, J = 8.0 Hz, 1H), 7.90 (d, J = 8.5 Hz, 1H), 7.76 (dd, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.61 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.56 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.46 (td, J = 7.5 Hz, J = 1.0 Hz, 1H), 7.33 (td, J = 8.0 Hz, J = 1.5 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 164.27, 150.78, 134.34, 134.09, 133.44, 132.10, 131.09, 131.05, 128.94, 127.90, 127.59, 127.40, 127.00, 126.17, 125.14, 121.97, 121.77.

2-(3,5-Difluorophenyl)naphtho[2,1-d]thiazole (3v)

Prepared according to the typical procedure as a yellow solid (30 mg, 50%). mp: 149–151 °C. 1H NMR (CDCl3, 500 MHz) δ 8.05 (d, J = 8.5 Hz, 1H), 7.98 (d, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.86 (d, J = 8.5 Hz, 1H), 7.63–7.54 (m, 4H), 6.91 (tt, J = 8.5 Hz, J = 2.5 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 163.99 (t, J = 3.5 Hz), 163.20 (dd, J = 248.0 Hz, J = 12.6 Hz), 151.95, 136.52 (t, J = 9.8 Hz), 132.53, 131.20, 128.99, 127.83, 127.19, 126.39, 125.10, 121.68, 110.09 (dd, J = 20.6 Hz, J = 7.0 Hz), 105.72 (t, J = 25.3 Hz). 19F NMR (CDCl3, 470 MHz) δ −108.35. HRMS (ESI) m/z calcd for C17H10F2NS+ (M + H)+: 298.0497, found: 298.0495.

2-(2,4-Difluorophenyl)naphtho[2,1-d]thiazole (3w)

Prepared according to the typical procedure as a yellow solid (20 mg, 33%). mp: 153–156 °C. 1H NMR (CDCl3, 500 MHz) δ 8.50–8.46 (m, 1H), 8.11 (d, J = 9.0 Hz, 1H), 8.07 (d, J = 8.0 Hz, 1H), 7.97 (d, J = 8.0 Hz, 1H), 7.89 (d, J = 8.5 Hz, 1H), 7.62 (t, J = 7.5 Hz, 1H), 7.56 (d, J = 7.5 Hz, 1H), 7.08–7.05 (m, 1H), 7.03–6.99 (m, 1H). 13C NMR (CDCl3, 125 MHz) δ 164.00 (dd, J = 252.5 Hz, J = 11.6 Hz), 160.56 (dd, J = 253.9 Hz, J = 11.9 Hz), 158.91 (d, J = 6.6 Hz), 150.59, 132.72 (d, J = 7.9 Hz), 131.04, 130.77 (dd, J = 9.9 Hz, J = 4.0 Hz), 128.98, 127.95, 127.56, 127.07, 126.17, 125.02, 121.52, 118.09 (dd, J = 11.5 Hz, J = 3.8 Hz), 112.43 (dd, J = 21.5 Hz, J = 3.1 Hz), 104.62 (t, J = 25.5 Hz). 19F NMR (CDCl3, 470 MHz) δ −105.85 (d, J = 9.4 Hz), −107.85 (d, J = 9.4 Hz). HRMS (ESI) m/z calcd for C17H10F2NS+ (M + H)+: 298.0497, found: 298.0495.

2-(3,5-Dimethoxyphenyl)naphtho[2,1-d]thiazole (3x)

Prepared according to the typical procedure as a yellow solid (48 mg, 74%). mp: 140–142 °C. 1H NMR (CDCl3, 500 MHz) δ 8.10 (d, J = 9.0 Hz, 1H), 8.02 (d, J = 8.5 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 9.0 Hz, 1H), 7.60 (td, J = 7.0 Hz, J = 1.0 Hz, 1H), 7.54 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.31 (d, J = 2.5 Hz, 2H), 6.59 (t, J = 2.0 Hz, 1H), 3.91 (s, 6H). 13C NMR (CDCl3, 125 MHz) δ 167.03, 161.14, 151.99, 135.40, 132.20, 131.06, 128.95, 128.02, 127.41, 127.00, 126.02, 125.13, 121.65, 105.19, 103.24, 55.60. HRMS (ESI) m/z calcd for C19H16NO2S+ (M + H)+: 322.0896, found: 322.0898.

2-(3,5-Bis(trifluoromethyl)phenyl)naphtho[1,2-d]thiazole (3y)

Prepared according to the typical procedure as a yellow solid (32 mg, 39%). mp: 184–186 °C. 1H NMR (CDCl3, 500 MHz) δ 8.55 (s, 2H), 8.11 (d, J = 9.0 Hz, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.98–7.97 (m, 2H), 7.92 (d, J = 9.0 Hz, 1H), 7.63 (t, J = 7.0 Hz, 1H), 7.58 (t, J = 7.0 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 163.01, 152.15, 135.67, 132.82, 132.61 (q, J = 33.5 Hz), 131.41, 129.10, 128.19, 127.88, 127.42, 127.04 (q, J = 3.4 Hz), 126.70, 125.19, 123.73 (q, J = 3.6 Hz), 123.02 (q, J = 271.3 Hz), 121.76. 19F NMR (CDCl3, 470 MHz) δ −62.94. HRMS (ESI) m/z calcd for C19H10F6NS+ (M + H)+: 398.0433, found: 398.0435.

2-Mesitylnaphtho[2,1-d]thiazole (3z)

Prepared according to the typical procedure as a colorless solid (37 mg, 63%). mp: 37–39 °C. 1H NMR (CDCl3, 500 MHz) δ 8.15 (d, J = 8.5 Hz, 1H), 8.05 (d, J = 8.0 Hz, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.91 (d, J = 9.0 Hz, 1H), 7.64–7.56 (m, 2H), 6.99 (s, 2H), 2.37 (s, 3H), 2.22 (s, 6H). 13C NMR (CDCl3, 125 MHz) δ 166.53, 151.44, 139.42, 137.36, 133.56, 133.33, 130.95, 130.64, 129.64, 128.96, 128.36, 128.06, 126.95, 125.98, 125.28, 121.86, 21.22, 20.18. HRMS (ESI) m/z calcd for C20H18NS+ (M + H)+: 304.1155, found: 304.1153.

2-(Pyridin-2-yl)naphtho[2,1-d]thiazole (3aa)[13]

Prepared according to the typical procedure as a yellow solid (17 mg, 32%). mp: 146–147 °C. 1H NMR (CDCl3, 500 MHz) δ 8.72 (d, J = 4.0 Hz, 1H), 8.41 (d, J = 8.0 Hz, 1H), 8.12 (t, J = 7.5 Hz, 2H), 7.98 (d, J = 8.0 Hz, 1H), 7.91–7.87 (m, 2H), 7.63 (t, J = 7.0 Hz, 1H), 7.58 (t, J = 7.0 Hz, 1H), 7.42–7.40 (m, 1H). 13C NMR (CDCl3, 125 MHz) δ 168.27, 152.38, 151.39, 149.68, 137.15, 133.72, 131.23, 128.96, 128.27, 127.55, 127.13, 126.34, 125.37, 125.10, 121.83, 120.48.

2-(Pyridin-3-yl)naphtho[2,1-d]thiazole (3ab)

Prepared according to the typical procedure as a yellow solid (32 mg, 62%). mp: 131–134 °C. 1H NMR (CDCl3, 500 MHz) δ 9.30 (d, J = 1.5 Hz, 1H), 8.69 (d, J = 4.0 Hz, 1H), 8.36 (d, J = 8.0 Hz, 1H), 8.06 (d, J = 9.0 Hz, 1H), 7.97 (d, J = 8.0 Hz, 1H), 7.93 (d, J = 8.0 Hz, 1H), 7.85 (d, J = 8.5 Hz, 1H), 7.58 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.53 (td, J = 8.0 Hz, J = 1.0 Hz, 1H), 7.40 (dd, J = 8.0 Hz, J = 4.5 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 163.48, 152.15, 151.30, 148.35, 134.28, 132.39, 131.22, 129.79, 129.03, 127.95, 127.80, 127.22, 126.35, 125.21, 123.83, 121.67. HRMS (ESI) m/z calcd for C16H11N2S+ (M + H)+: 263.0638, found: 263.0637.

2-(Pyridin-4-yl)naphtho[2,1-d]thiazole (3ac)

Prepared according to the typical procedure as a brown solid (8 mg, 16%). mp: 140–143 °C. 1H NMR (CDCl3, 500 MHz) δ 8.78 (d, J = 5.5 Hz, 2H), 8.12 (d, J = 8.5 Hz, 1H), 8.06 (d, J = 7.5 Hz, 1H), 8.00–7.98 (m, 3H), 7.92 (d, J = 9.0 Hz, 1H), 7.64 (t, J = 7.0 Hz, 1H), 7.59 (td, J = 8.0 Hz, J = 1.0 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 163.88, 152.21, 150.63, 140.59, 132.93, 131.38, 129.08, 128.05, 127.90, 127.33, 126.67, 125.27, 121.83, 120.96. HRMS (ESI) m/z calcd for C16H11N2S+ (M + H)+: 263.0638, found: 263.0637.

2-(Thiophen-2-yl)naphtho[2,1-d]thiazole (3ad)[10]

Prepared according to the typical procedure as a yellow solid (33 mg, 61%). mp: 122–125 °C. 1H NMR (CDCl3, 500 MHz) δ 8.06 (d, J = 9.0 Hz, 1H), 7.94 (t, J = 7.0 Hz, 2H), 7.85 (d, J = 9.0 Hz, 1H), 7.68 (d, J = 3.5 Hz, 1H), 7.58 (t, J = 7.0 Hz, 1H), 7.52 (t, J = 8.0 Hz, 1H), 7.49 (d, J = 5.0 Hz, 1H), 7.14 (t, J = 4.0 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 160.56, 151.72, 137.37, 131.63, 131.03, 128.95, 128.87, 128.09, 128.04, 127.89, 127.47, 127.00, 125.93, 124.96, 121.43.

2-(Naphthalen-1-yl)naphtho[2,1-d]thiazole (3ae)[13]

Prepared according to the typical procedure as a yellow solid (49 mg, 80%). mp: 95–97 °C. 1H NMR (CDCl3, 500 MHz) δ 9.05 (d, J = 8.5 Hz, 1H), 8.24 (d, J = 8.5 Hz, 1H), 8.08 (d, J = 8.0 Hz, 1H), 8.01–7.99 (m, 3H), 7.96–7.93 (m, 2H), 7.68–7.65 (m, 1H), 7.64–7.57 (m, 4H). 13C NMR (CDCl3, 125 MHz) δ 166.61, 152.17, 133.99, 132.66, 131.01, 130.90, 130.81, 130.61, 129.35, 128.95, 128.38, 127.93, 127.59, 127.33, 126.98, 126.46, 126.03, 125.88, 125.34, 125.00, 121.91.

7-Bromo-2-phenylnaphtho[2,1-d]thiazole (3ba)

Prepared according to the typical procedure as a yellow solid (52 mg, 76%). mp: 170–172 °C. 1H NMR (CDCl3, 500 MHz) δ 8.11–8.08 (m, 4H), 7.85 (d, J = 8.5 Hz, 1H), 7.75 (d, J = 9.0 Hz, 1H), 7.65–7.63 (m, 1H), 7.51–7.50 (m, 3H). 13C NMR (CDCl3, 125 MHz) δ 167.52, 152.36, 133.40, 132.14, 131.01, 130.92, 130.17, 129.09, 127.31, 126.66, 126.51, 126.39, 122.75, 119.73. HRMS (ESI) m/z calcd for C17H11BrNS+ (M + H)+: 339.9790, found: 339.9791.

2-Methylnaphtho[2,1-d]thiazole (3ak)

Prepared according to the typical procedure as a bronzing liquid (11 mg, 28%). 1H NMR (CDCl3, 500 MHz) δ 8.00 (d, J = 8.5 Hz, 1H), 7.96 (d, J = 8.5 Hz, 2H), 7.85(d, J = 9.0 Hz, 1H), 7.58 (t, J = 7.5 Hz, 1H), 7.53 (t, J = 7.5 Hz, 1H), 2.92 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 165.91, 151.25, 132.45, 130.82, 128.92, 128.02, 126.97, 126.88, 125.70, 125.03, 121.15, 20.13. HRMS (ESI) m/z calcd for C12H10NS+ (M + H)+: 200.0529, found: 200.0528.

2-Isopropylnaphtho[2,1-d]thiazole (3al)

Prepared according to the typical procedure as a yellow liquid (9 mg, 19%). 1H NMR (CDCl3, 500 MHz) δ 8.02 (d, J = 9.0 Hz, 1H), 7.98 (d, J = 8.5 Hz, 1H), 7.95 (d, J = 8.5 Hz, 1H), 7.85 (d, J = 9.0 Hz, 1H), 7.58 (td, J = 7.0 Hz, J = 1.0 Hz, 1H), 7.52 (td, J = 7.5 Hz, J = 1.0 Hz, 1H), 3.55–3.47 (m, 1H), 1.55 (s, 3H), 1.54 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 177.74, 151.08, 131.55, 130.78, 128.92, 128.20, 126.89, 126.83, 125.63, 124.99, 121.37, 34.11, 23.13. HRMS (ESI) m/z calcd for C14H13NS+ (M + H)+: 227.0769, found: 227.0763.

5-Methoxy-2-phenylbenzo[d]thiazole (4a)[13]

Prepared according to the typical procedure as a yellow solid (23 mg, 42%). mp: 75–77 °C. 1H NMR (CDCl3, 500 MHz) δ 8.08–8.06 (m, 2H), 7.74 (d, J = 8.5 Hz, 1H), 7.58 (d, J = 2.5 Hz, 1H), 7.49–7.48 (m, 3H), 7.04 (dd, J = 9.0 Hz, J = 2.5 Hz, 1H), 3.91 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 169.26, 159.09, 155.31, 133.65, 130.86, 128.97, 127.34, 126.83, 121.80, 115.84, 105.42, 55.57.

N,N-Dimethyl-2-phenylbenzo[d]thiazol-5-amine (4b)[13]

Prepared according to the typical procedure as a yellow solid (35 mg, 72%). mp: 87–90 °C. 1H NMR (CDCl3, 500 MHz) δ 8.09–8.07 (m, 2H), 7.70 (d, J = 9.0 Hz, 1H), 7.48–7.47 (m, 3H), 7.40 (d, J = 2.0 Hz, 1H), 7.93 (dd, J = 9.0 Hz, J = 2.5 Hz, 1H), 3.03 (s, 6H). 13C NMR (CDCl3, 125 MHz) δ 168.53, 155.74, 150.16, 133.88, 130.59, 128.87, 127.26, 123.12, 121.41, 113.13, 105.63, 41.07.

N-(2-Phenylbenzo[d]thiazol-5-yl)acetamide (4c)

Prepared according to the typical procedure as a yellow solid (29 mg, 55%). mp: 184–186 °C. 1H NMR (CDCl3, 500 MHz) δ 8.17 (d, J = 1.5 Hz, 1H), 8.06–8.04 (m, 2H), 7.80 (d, J = 9.0 Hz, 1H), 7.76 (s, 1H), 7.64 (dd, J = 8.5 Hz, J = 2.0 Hz, 1H), 7.49–7.48 (m, 3H), 2.22 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 169.31, 168.58, 154.52, 136.70, 133.41, 131.05, 130.57, 129.01, 127.47, 121.70, 118.46, 113.89, 24.61. HRMS (ESI) m/z calcd for C15H13N2OS+ (M + H)+: 269.0743, found: 269.0744.

5-(Benzyloxy)-2-phenylbenzo[d]thiazole (4d)

Prepared according to the typical procedure as a white solid (36 mg, 60%). mp: 124–125 °C. 1H NMR (CDCl3, 500 MHz) δ 8.08–8.06 (m, 2H), 7.76 (d, J = 9.0 Hz, 1H), 7.65 (d, J = 2.5 Hz, 1H), 7.50–7.49 (m, 5H), 7.42 (t, J = 7.5 Hz, 2H), 7.35 (t, J = 7.5 Hz, 1H), 7.13 (dd, J = 8.5 Hz, J = 2.5 Hz, 1H), 5.18 (s, 2H). 13C NMR (CDCl3, 125 MHz) δ 169.29, 158.16, 155.21, 136.63, 133.60, 130.89, 128.99, 128.61, 128.05, 127.53, 127.35, 127.11, 121.88, 116.10, 106.63, 70.33. HRMS (ESI) m/z calcd for C20H17N2S+ (M + H)+: 317.1107, found: 317.1107.

5,7-Dimethoxy-2-phenylbenzo[d]thiazole (4e)[13]

Prepared according to the typical procedure as a yellow solid (47 mg, 84%). mp: 84–85 °C. 1H NMR (CDCl3, 500 MHz) δ 8.08–8.07 (m, 2H), 7.49–7.47(m, 3H), 7.20 (d, J = 2.0 Hz, 1H), 6.50 (d, J = 2.0 Hz, 1H), 3.96 (s, 3H), 3.90 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 169.24, 160.35, 155.74, 154.30, 133.66, 130.79, 128.97, 127.29, 116.21, 97.50, 96.90, 55.90, 55.74.

5-Methoxy-7-methyl-2-phenylbenzo[d]thiazole (4f)

Prepared according to the typical procedure as a white solid (47 mg, 93%). mp: 83–85 °C. 1H NMR (CDCl3, 500 MHz) δ 8.09–8.07 (m, 2H), 7.51–7.48 (m, 3H), 7.42 (d, J = 2.0 Hz, 1H), 6.85 (d, J = 1.0 Hz, 1H), 3.88 (s, 3H), 2.54 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 168.47, 159.21, 154.80, 133.74, 132.08, 130.74, 128.94, 127.63, 127.25, 115.54, 102.80, 55.52, 21.41. HRMS (ESI) m/z calcd for C15H14NOS+ (M + H)+: 256.0791, found: 256.0790.

5,6-Dimethoxy-2-phenylbenzo[d]thiazole (4g)[10]

Prepared according to the typical procedure as a yellow solid (48 mg, 88%). mp: 143–147 °C. 1H NMR (CDCl3, 500 MHz) δ 8.02–8.01 (m, 2H), 7.54 (s, 1H), 7.48–7.42 (m, 3H), 7.28 (s, 1H), 3.97 (s, 3H), 3.95 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 166.16, 149.31, 148.45, 148.34, 133.68, 130.35, 128.91, 126.92, 104.53, 102.26, 56.21, 56.03.

5,6,7-Trimethoxy-2-phenylbenzo[d]thiazole (4h)[10]

Prepared according to the typical procedure as a yellow solid (28 mg, 46%). mp: 56–60 °C. 1H NMR (CDCl3, 500 MHz) δ 8.05–8.03 (m, 2H), 7.50–7.46 (m, 3H), 7.36 (s, 1H), 4.10 (s, 3H), 3.95 (s, 3H), 3.94 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 167.92, 153.92, 150.41, 146.68, 139.68, 133.51, 130.69, 128.96, 127.14, 120.20, 100.62, 61.44, 60.52, 56.21.

5,6,7-Trimethyl-2-phenyl-6,7-dihydrobenzo[d]thiazole (4i)

Prepared according to the typical procedure as a yellow solid (35 mg, 67%). mp: 74–76 °C. 1H NMR (CDCl3, 500 MHz) δ 8.09–8.07 (m, 2H), 7.75 (s, 1H), 7.50–7.47 (m, 3H), 2.54 (s, 3H), 2.43 (s, 3H), 2.31 (s, 3H). 13C NMR (CDCl3, 125 MHz) δ 166.47, 151.56, 135.76, 134.17, 133.89, 132.22, 130.52, 128.89, 128.83, 127.28, 121.35, 21.32, 20.12, 15.62. HRMS (ESI) m/z calcd for C16H16NS+ (M + H)+: 254.0998, found: 254.0996.