Rhodium-catalyzed rapid synthesis of substituted phenols from cyclobutenones and alkynes or alkenes via C–C bond cleavage

A novel rhodium-catalyzed synthesis of substituted phenols by the ring-opening reaction of cyclobutenones with alkynes as well as electron-deficient alkenes has been developed. Both reactions involve C–C bond cleavage of cyclobutenones, and an (η4-vinylketene)rhodium complex rather than a rhodacyclopentenone is considered to be a key intermediate.