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

Tetrahydropyran‐4‐one and tetrahydrothiopyran‐4‐one derivatives with a 3‐aryl substituent were synthesized by double‐conjugate addition of water or H2S 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 MnO2. 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)