Condensation of fluorinated carbonyl compounds with halobenzenes

Fluoro- or chlorobenzenes undergo the Friedel-Crafts acylation with perfluoroacyl chlorides (I) without complications to give p-halophenylketones (II); however, the reaction of I with bromobenzene gives phenylketones (IV) and dibromobenzene in addition to p-bromophenylketones (III). An intermediate p-bromobenzyl cation (V) is assumed to be responsible for the formation of the abnormal products TV and dibromobenzene. Condensation of hexafluoroacetone with bromobenzene in anhydrous HF also affords the products of disproportionation probably via an intermediate benzyl cation (IX). (C) 1998 Elsevier Science S.A. All rights reserved.