Novel synthesis of benzothiazole by self-redox tandem reaction of disulfide with aldehyde

A novel methodology for the preparation of benzothiazole derivatives via the reaction of ortho-anilino disulfides with aryl and heteroaryl aldehydes catalyzed by Na2S·9H2O has been developed. The reaction mechanism was investigated by LC-MS and 1H NMR. The disulfide was cleaved firstly by the interchange reaction of the disulfide and metal sulfide, and the resulting thiol reacted in situ with the aldehyde to form the corresponding benzothiazoline. Subsequently, the intermediate benzothiazoline reduced the disulfide to thiol and it was oxidized to benzothiazole. The excess benzothiazoline was oxidized by air and both halves of the disulfide were ultimately converted to the desired benzothiazole.