Ytterbium Trif late Catalyzed Synthesis of Alkoxy-Substituted Donor-Acceptor Cyclobutanes and Their Formal [4+2] Cycloaddition with Imines: Stereoselective Synthesis of Piperidines

A new synthesis of 2-alkoxy-1,1-cyclobutane diesters and their first use in dipolar cycloadditions is reported. Both the formation of the donor-acceptor cyclobutanes and their subsequent annulation with in situ formed imines are catalyzed by Yb(OTf)(3). Cyclobutanes with carbon donor groups give piperidines with high trans stereoselectivity.