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Palladium-Catalyzed Synthesis of Benzothiazoles Using a Thiol Surrogate
T. Itoh*, T. Mase
Banyu Pharmaceutical Co. Ltd., Ibaraki, Japan
22 November 2007 (online)
Reported here is a one-pot procedure for the synthesis of benzothiazoles from the reaction of 2-bromobenzanilides with 2-ethylhexyl 3-mercaptopropionate in presence of catalytic Pd2(dba)2/XantPhos. The mercaptopropionate is used as a thiol surrogate which is released from the coupled product by β-elimination for the final cyclization to benzothiazole. Neutral or electron-deficient carbonyl amides were easily cyclized under basic conditions. Anilides with EWGs and substrates with electron-rich carbonyl amides undergo effective cyclization under acidic conditions. (4-Methoxyphenyl)methanethiol may be used as an alternative thiol surrogate.