TMSCl Promoted Direct sp3C-H Alkenylation to Construct (E)-2-Styryl-tetrahydrobenzo[d]thiazoles

A high-efficient and stereo-specific approach for the preparation of biologically important (E)-2-styryl-tetrahydrobenzo[d]thiazoles has been developed via TMSCl promoted direct sp3 C-H alkenylation of 2-methyl-5,6-dihydrobenzo[d]thiazol-7(4H)-one under metal-free conditions. Seventeen target compounds were synthesized in excellent yields of 82% –98% under the optimal conditions of 300 mol% TMSCl at 110°C for 2 h, and their chemical structures were elucidated by IR, NMR, ESI-MS, elemental analyses and X-ray crystallography analysis. A plausible mechanism was also proposed, and this method provided a good functional group conversion for the sp3 C-H substrates.