A Convenient Synthetic Route to Functionalized 5-Trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2H-pyrans: Hetero-Diels-Alder Reaction of β,β-Bis(trifluoroacetyl)vinyl Ethers with Electron-Rich Alkenes

Abstract

Hetero-Diels-alder reaction of β,β-bis(trifluoroacetyl)vinyl ethers, which are prepared by acylation of vinyl ethers with trifluoroacetic anhydride, with electron-rich alkenes such as vinyl ethers, ethyl vinyl sulfide and 1,1-diphenoxyethylene proceed quite easily under mild conditions to afford 2,4-dialkoxy-, 2-ethoxy-4-phenoxy-, 2-ethylthio-4-alkoxy-, 2-2diphenoxy-4-ethoxy- and 2,4-diaryloxy-5-trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2H-pyrans in excellent yields