Base-mediated diastereoselective [4 + 3] annulation of in situ generated ortho-quinone methides with C,N-cyclic azomethine imines.

An efficient [4 + 3] annulation of 2-(1-tosylalkyl)phenols with C,N-cyclic azomethine imines via in situ generation of ortho-quinone methides (o-QMs) under mild basic reaction conditions is disclosed, furnishing biologically interesting seven-membered heterocyclic compounds with moderate to good yields and excellent diastereoselectivities. A gram-scale reaction is performed to demonstrate the potential in industrial application and two transition states are proposed to rationalize the outstanding diastereoselectivity.