Construction of cyclopenta[b]pyran-2-ones via chemoselective (3 + 2) cycloaddition between 2-pyrones and vinyl cyclopropanes. Issue 6 (24th February 2020) - Liang, Xuefeng
Abstract : A chemoselective (3 + 2) cycloaddition of 2-pyrones and vinyl cyclopropanes for efficient and diastereoselective synthesis of cyclopenta[ b ]pyran-2-ones. 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.