Facile Ionic Liquid–Mediated Protocol for the Regioselective Synthesis of 1,5-Benzothiazepines

Abstract

An efficient one-step ionic liquid–mediated green protocol for the regioselective synthesis of (+)/(±)-cis-2-(4-methoxy/benzyloxyphenyl)-3-hydroxy-2,3-dihydro-1,5-benzothiazepin-4-[5H]-ones has been developed from the reaction between substituted 2-aminobenzenethiol and methyl-(±)-trans-3-(4-methoxy/benzyloxy phenyl)glycidate, under nitrogen atmosphere, at 60 ± 2 °C. The reaction has been performed in ionic liquids (viz, 1-butyl-3-methylimidazolium bromide/hexafluorophosphate), and the yields of the 1,5-benzothiazepine derivatives were found to be excellent. The cis-stereoisomer was obtained as the major product along with a trans-isomer as minor product.

Keywords:

• Benzothiazepines
• glycidate
• green chemistry
• ionic liquids
• regioselectivity

ACKNOWLEDGMENTS

We thank the head of the Department of Chemistry, University of Rajasthan, Jaipur, for providing laboratory facilities. We are also grateful to Central Drug Research Institute (CDRI), Lucknow, for some analytical data. Financial assistance from the University Grants Commission, New Delhi, is thankfully acknowledged.

Notes

^a Total yield of cis and trans isomers (compounds 3 and 4).