One-Pot Preparation of 2-(Alkyl)arylbenzothiazoles from the Corresponding o-Halobenzanilides

Abstract

Thionation of o-halobenzanilides was carried out in the presence of Lawesson’s reagent. Subsequently, the formed thio­amides reacted with cesium carbonate to give the corresponding benzothiazole derivatives in the same pot.

Key words

one-pot reaction - benzothiazole - cesium carbonate - Lawesson’s reagent - cyclization

References and Notes

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• 3b Chakraborti AK. Selvam C. Kaur G. Bhagat S. Synlett  2004,  851 ; and references cited in these articles
• Sodium hydride:
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• 8 Compound 6 was prepared according to literature procedure: Shimada T. Nakamura I. Yamamoto Y. J. Am. Chem. Soc.  2004,  126:  10546 
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• 13 During this study we used commercial and synthesized LR, prepared according to the literature procedure: Pedersen BS. Scheibye S. Nilsson NH. Lawesson S.-O. Bull. Soc. Chim. Belg.  1978,  87:  223 

1

Current address (postdoctoral fellow): Service de Marquage Moléculaire et de Chimie Bioorganique, DSV/DBJC, CEA/Saclay, 91191 Gif-sur-Yvette, France; email: [e-mail], [e-mail].

12

Typical Procedure: In a 10-mL flask were placed the appropriate amide (1.17 mmol), Lawesson’s reagent¹³ (0.6 equiv, 0.29 g), xylene (3 mL) and a magnetic stirring bar. The mixture was stirred under argon at 105-115 °C for 2.5 h. Then Cs₂CO₃ (2 equiv, 0.81 g)was added and the reaction mixture was stirred under reflux for the indicated time. The solvent was evaporated to dryness and the crude product was chromatographed on silica gel (cyclohexane-EtOAc, 97:3) to afford the desired benzothiazole derivative.