Convergent Synthesis of Dihydropyrans from Catalytic Three-Component Reactions of Vinylcyclopropanes, Diazoesters, and Diphenyl Sulfoxide

A novel Rh­(I)/La­(III) cocatalytic three-component reaction of vinylcyclopropanes, diazoesters, and diphenyl sulfoxide has been developed. The reaction gives polysubstituted dihydropyrans as the reaction products. Mechanistic studies indicate that isomerization of vinylcyclopropanes gives conjugated dienes, which then undergo [4 + 2]-cycloaddition with vicinal tricarbonyl compounds generated by oxygen atom transfer from diphenyl sulfoxide to diazoesters.