A Microwave Synthesis of the cis‐ and trans‐Isomers of 3‐Hydroxy‐2‐(4‐ methoxyphenyl)‐2,3‐dihydro‐1,5‐benzothiazepin‐4(5H)‐one: The Influence of Solvent and Power Output on the Diastereoselectivity.

A diastereoselective one-pot synthesis of the trans- and cis-3-hydroxy-2-(4-methoxyphenyl)-2,3-dihydro-1,5-benzothiazepin-4(5H)-one nucleus, a key intermediate in the preparation of the calcium channel blocker Diltiazem, is carried out under microwave irradiation in an open vessel. Control of the diastereoselectivity is achieved by varying the reaction time and power output as well as the nature of the solvent.