THE KINETIC IMPACT OF VINYLIC FLUORINE SUBSTITUENTS ON 5-HEXENYL RADICAL CYCLIZATIONS

A study of the effect of vinylic fluorine substituents on the 5-hexeny l radical cyclization indicates that substituents at the 6-position, o r vicinal 5,6-difluoro substitution have little effect on the rate, wh ereas a 5-fluoro substituent slows down the rate by a factor of 10.8, and 5,6,6-trifluoro substitution enhances the tate by a factor of 2.3. The results are explained in terms of a combination of steric and ent halpic effects, with possible intervention of polar influences in the trifluorovinyl case. Copyright (C) 1996 Elsevier Science Ltd