syn-2,3-disubstituted-2,3-dihydro-1,4-benzoxathiin rings:: preparation from quinone ketals and 2-mercaptoethanols

A general method for the preparation of syn-2,3-disiubstitutedted-2,3-dihydro-1,4-benzoxathiin rings from 2-mercaptoethanols and quinone keta s is presented. This ring system is produced by Michael addition of a 2-mercaptocthanol to a quinone ketal, followed by cyclization of the initial Michael adduct, and Subsequent aromatization to afford a syn-2,3-disubstituted-1,4benzoxathiin in fair to good chemical yield. Several chiral syn-2,3-disubstituted-2,3-dihydro-1,4-benzoxathiin rings were prepared with this method from enantioenriched 2-mercaptoethanols. No loss of enantiopurity was observed. (C) 2004 Elsevier Ltd. All rights reserved.