High Diastereoselectivity in the Yang Photocyclization via Remote Hydrogen Abstraction Reaction

Abstract

1-Benzoyl-1-(o-alkoxyphenyl)cyclopropanes undergo Yang photocyclization to form dihydrobenzo-pyranols in a stereospecific manner. The cyclopropyl group at alpha position to carbonyls gives not only a bias in the most stable geometries of the starting ketones but also conformational restriction on geometries of biradical intermediates. More importantly, intramolecular hydrogen bonds seem to give an additional effect on conformational control of the biradical reactivity.