Construction of cyclopenta[b]pyran-2-ones via chemoselective (3 + 2) cycloaddition between 2-pyrones and vinyl cyclopropanes

Abstract

A method for synthesising cyclopenta[b]pyran-2-ones through direct (3 + 2) cycloaddition between 2-pyrones and vinyl cyclopropanes is described. In the presence of Pd₂(dba)₃/dppe in toluene, a series of 2-pyrones undergo chemoselective (3 + 2) cycloaddition with vinyl cyclopropanes and afford cyclopenta[b]pyran-2-ones in high yields (78–96%). The trans/cis ratio of the cycloadducts has been optimised up to 10 : 1. The proposed mechanism of this cycloaddition has been rationalised by computational studies.