Functionalized Azetidines Via Visible Light-Enabled Aza Paternò-Büchi Reactions

Azetidines are four-membered nitrogen-containing heterocycles that hold great promise in current medicinal chemistry due to their desirable pharmacokinetic effects. However, a lack of efficient synthetic methods to access functionalized azetidines has hampered their incorporation into pharmaceutical lead structures. As [2+2] cycloaddition reaction between imines and alkenes, the aza Paternò-Büchi reaction arguably represents the most direct approach to functionalized azetidines. Currently, competing reaction paths accessible upon photochemical excitation of the substrates greatly restrict the synthetic utility of these transformations. We herein report the development of a visible light-enabled aza Paternò-Büchi reaction that surmounts existing limitations and represents a general solution for the direct formation of functionalized azetidines from imine and alkene containing precursors.