Excited state substitution and addition reactions of aryl fluorides with aliphatic amines

Abstract

Fluorobenzene and the difluorobenzenes undergo photochemical reaction with t-butylamine and diethylamine to give both 1 : 1 adducts and substitution products but only the latter are formed from hexafluorobenzene and diethylamine. Both cine and ‘normal’ substitution products are observed from the difluoro-compounds and the mechanism to account for this is considered to involve a polar excited-state complex between the addends and an addition–elimination process rather than benzyne intermediates. 1,2-Acyclic amine photoadducts are produced from most systems but the corresponding 1,4-isomers are the major adducts from p-difluorobenzene and that from diethylamine is unique in undergoing thermal retro-addition to the starting materials rather than conversion into the aniline derivative.