Synthesis of glycoconjugate benzothiazoles via cleavage of benzotriazole ring.

A concise and efficacious benzotriazole-mediated novel two-step protocol has been developed for easy access to glycoconjugate benzothiazoles from protected carbohydrates. The benzotriazolemethanethione 3, prepared by the reaction of free alcohol with bis(1H-benzo[1,2,3]triazol-1-yl)methanethione, on treatment with silanes or stannane under heating or microwave irradiation undergoes free radical β-scission of N-N bond and affords diverse range of 2-O-substituted benzothiazoles 4 via cyclative elimination of molecular nitrogen. The structures of all of the compounds have been elucidated using IR, NMR, MS, and elemental analysis, and five of them have been characterized by single-crystal X-ray analysis.