The coupling of highly oxygenated ortho-alkynylbenzaldehyde derivatives with γ, δ-carbene complexes was evaluated systematically. In all of the electron-rich systems investigated the exclusive product of the reaction is the dihydrophenanthrene derivative. Only the extremely electron-withdrawing methanesulfonate group can prevent this process from occurring. The use of the base additive collidine resulted in a surprising yield enhancement but no other ...
