Elemental Sulfur-Mediated Decarboxylative Redox Cyclization ­Reaction: Copper-Catalyzed Synthesis of 2-Substituted Benzo­thiazoles

Abstract

A S8-mediated directed decarboxylative redox-cyclization strategy for the synthesis of 2-substituted benzothiazoles from o-iodoanilines, arylacetic acids, and elemental sulfur catalyzed by cheap copper metal has been developed. This reaction is operationally simple, ligand-free, compatible with a wide range of functional groups, and provides the desired products in good to excellent yields. In addition, a gram-scale experiment was carried out to furnish PMX 610, an antitumor drug.

Recent Advances in the Synthesis of Heterocycles via Reactions Involving Elemental Sulfur

“…Sulfur could be used as a sulfide source in the reaction with an o-iodoaniline 212 to provide the coresponding 2-aminothiophenol, which could further involve in an oxidative condensation reaction with a suitable C-2 precursor 213 and result in 2-substituted benzothiazoles 214 (Scheme 70). [75][76][77][78][79][80][81][82] Benzaldehydes (entries 1-2), benzylamines (entries 3-4), dibenzyl disulfides (entry 5), phenylacetic acids (entry 6), benzyl chlorides (entry 7) could be used as C-2 precursor. Phase transfer agents such as tetrasubstituted ammonium salts could also be used for this purpose.…”

Transition Metal‐Free Oxidative Coupling of Primary Amines in Polyethylene Glycol at Room Temperature: Synthesis of Imines, Azobenzenes, Benzothiazoles, and Disulfides

“…Table , Entry 6e: White crystal; 1 H NMR (400 MHz, CDCl 3 ): δ = 8.13 (d, J = 7Hz, 1H), 8.00 (s, 1H), 7.90 (t, J = 7Hz, 2H), 7.53 (m, 1H), 7.40 (t, J = 7Hz, 2H), 7.32 (d, J = 7Hz, 1H), 2.48 (s, 3H); 13 C NMR (101 MHz, CDCl 3 ): δ = 168.3, 154.2, 138.8, 135.1, 133.5, 131.8, 128.9, 128.0, 126.3, 125.1, 124.9, 123.2, 121.6, 21.4; HRMS (ESI) m/z : calcd. for C 14 H 11 NS [M + H] + 226.0690, found 226.0685.…”