Synthesis of Tetrahydropyran‐4‐ones and Thiopyran‐4‐ones from Donor‐Substituted α‐Bromostyrene Derivatives

Abstract

Abstract Tetrahydropyran‐4‐one and tetrahydrothiopyran‐4‐one derivatives with a 3‐aryl substituent were synthesized by double‐conjugate addition of water or H 2 S to divinyl ketones. These starting materials were prepared in two steps by conversion of lithiated α‐bromostyrene derivatives with acrolein or cinnamaldehyde and subsequent oxidation of the divinyl alcohols with MnO 2 . The electron‐rich α‐bromostyrene building blocks were prepared by addition of HBr to the respective alkyne under strictly anhydrous conditions, which works reliably on a multigram scale. Two routes to arylacetylenes with a specific substitution pattern have been explored; however, on a larger scale only the Corey–Fuchs sequence turned out to be feasible.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)