Study of a model system for asymmetric induction in [2C + 2C] photoannelation reactions

Abstract

Photocycloaddition of cyclopent-2-enone and (S)-(+)-2-methyl-1-(2-methylbutoxy)-1-trimethylsilyl-oxyprop-1-ene leads both to oxetanes and cyclobutanes. The asymmetric induction, experimentally determined, in the head-to-tail [2C + 2C] cyclobutane adducts amounts to about 30%, but the intrinsic induction is nearly quantitative. The absolute configuration of the predominant enantiomer conforms to that expected from the sterically preferred reaction mode. The chiral handle can easily be recovered and recycled.