Direct Activation of Unmodified Morita-Baylis-Hillman Alcohols through Phosphine Catalysis for Rapid Construction of Three-Dimensional Heterocyclic Compounds.

The phosphine-catalyzed tandem annulation reaction of Morita-Baylis-Hillman (MBH) alcohols with azomethine imines has been achieved for the synthesis of biologically important (epoxymethano)-pyrazolo[5,1- b]quinazoline derivatives. A variety of MBH alcohols and azomethine imines were well-tolerated under the mild reaction conditions, providing novel 3D heterocyclic compounds in high yields with excellent diastereoselectivities. It is the first time the direct activation of unmodified MBH alcohols acting as new oxa-synthons has been achieved.