Rhodium Carbenoid Initiated O–H Insertion/Aldol/Oxy-Cope Cascade for the Stereoselective Synthesis of Functionalized Oxacycles

A novel diazo-cascade approach has been developed for the synthesis of nine-membered oxacycles utilizing readily accessible β-hydroxy vinyl ketones and vinyl diazo esters. The Rh­(II)-catalyzed cascade reaction begins with carbene O–H insertion followed by an intramolecular aldol cyclization to provide a substituted tetrahydrofuran intermediate that undergoes an oxy-Cope rearrangement to provide functionalized nine-membered oxacycles with complete stereoselectivity