KO^tBu-Promoted Halogen-Bond-Assisted Intramolecular C–S Cross-Coupling of o-Iodothioanilides for the Synthesis of 2-Substituted Benzothiazoles

Abstract

An efficacious and mild KO t Bu-promoted intramolecular C−S cross-coupling of ortho-iodothioanilides in conjunction with a catalytic quantity of phenanthroline as an additive has been described for the convenient synthesis of 2-substituted benzothiazoles. The methodology is suitable for attaining a wide variety of 2-alkyl-and 2-aryl-substituted benzothiazoles. Singlecrystal XRD, DFT calculations, NMR, and UV studies suggest that halogen bonds between the units of ortho-iodothioanilides may assist in the electron transfer process.

Metal- and base-free, aerobic photoredox catalysis with riboflavin to synthesize 2-substituted benzothiazoles

“…24,25 Benzothiazoles are also obtained by the cyclization of thiobenzanilides [26][27][28][29][30] or 2-halothioformanilides. [31][32][33][34] Additionally, elemental sulphur can be used as a chalcogenide source in trimolecular approaches to obtain benzothiazoles by a copper-catalyzed 35,36 or by a copperfree method (Scheme 1). 37 These methodologies are associated, to a greater or lesser extent, with many disadvantages such as harsh reaction conditions, metallic catalysts, stoichiometric or excess amounts of strong oxidizing agents, basic conditions, prolonged reaction times, and toxic solvents.…”

“…24,25 Benzothiazoles are also obtained by the cyclization of thiobenzanilides 26–30 or 2-halothioformanilides. 31–34 Additionally, elemental sulphur can be used as a chalcogenide source in trimolecular approaches to obtain benzothiazoles by a copper-catalyzed 35,36 or by a copper-free method (Scheme 1). 37…”

Goldberg Coupling of Thiazole Substituted Aryl Bromide Demands Stoichiometric Copper Compared to Oxazole

“…[19] However, there are limited examples for transition metal catalyzed transformation of thiazole derivatives. [19][20] The cross-coupling approach provides a divergent method for the synthesis of highly functionalized derivatives of the core structure. Recently, transition metal-catalyzed CÀ N cross-coupling reactions have been used widely in academia as well as in industries.…”

“…Due to the immense importance of thiazole derivatives, there is a vast literature on the synthesis and derivatization of thiazole heterocycle [19] . However, there are limited examples for transition metal catalyzed transformation of thiazole derivatives [19–20] …”

Transition Metal-Free Iodine-Catalyzed Denitrative C–S Cross-Coupling: An Atypical Route to Access Thiochromane Derivatives

“…Our group has been actively involved in developing methodologies to construct various organosulfur compounds through C–S bond formation over the past decade . Building upon this, we envisaged attaining organosulfur compounds from easily accessible and inexpensive 2′-nitrochalcones 1a with xanthate as an odorless sulfur surrogate (Scheme c).…”