Unravelling the Nucleophilicity of Butenolides for 1,6-Conjugate Addition to p-Quinone Methides: A Direct Access to Diversely Substituted Butenolide-Derived Diarylmethanes.

A Lewis acid catalyzed regioselective C-C bond is constructed through β-addition of deconjugated butenolides with p-quinone methides in a 1,6-conjugate addition manner. Interestingly, Lewis acid catalyzed vinylogous Mukaiyama-Michael reaction of silyloxyfurans with p-QMs proceeds selectively through the α or γ position exclusively. The reaction is mild with broad substrate scope, thus allowing easy access to a wide range of bis-arylated α-/β-/γ-substituted butenolides.