Exo-selective formation of bicyclic oxetanes in the photocycloaddition reaction of carbonyl compounds with vinylene carbonate: The important role of intermediary triplet diradicals in the stereoselectivity

Abstract

The photochemical [2+2] cycloaddition reaction, the Paternò- Büchi (PB) reaction, of carbonyl compounds 1a-d with vinylene carbonate (2) was used to synthesize oxetanodioxolanones 3. The reaction involves the exo-selective (exo/endo > 83/17) formation of the bicyclic oxetanes 3b-d. Computational studies were performed to reveal the equilibrium structures of the intermediary triplet diradicals and their conformational distribution, which play an important role in determining the stereoselectivity of such PB reactions. ©ARKAT USA, Inc.