THE QUASI-HOMO-ANOMERIC INTERACTION IN SUBSTITUTED TETRAHYDROPYRANYL RADICALS - DIASTEREOSELECTIVITY

The isomer distribution of products from the reaction of a range of si mple cyclohexyl and tetrahydropyranyl radicals (3 -7) with Bu3SnD and with allyltributyltin, has been determined in order to gauge the influ ence of the classical anomeric effect and the quasi-homo-anomeric effe ct on stereoselectivity. In these unencumbered radicals, both anomeric effects caused a strong preference for bans deuterated products, but no significant stereoselectivity was observed for the allylation react ions. The difference between the two types of reaction suggests that d euteration is mainly under kinetic control whereas allylation has a gr eater tendency for thermodynamic control. (C) 1998 Elsevier Science Lt d. All rights reserved.