Oxidative Coupling of 6,6-Dimethylfulvenyl Anion

Abstract

Oxidative treatment of anion 1 (obtained by deprotonation of 6,6-dimethylpentafulvene) with CuCl2 gives a very complex mixture of coupling products 3 (18%), 4 (16%), 5 (36%), 6 (5%), and 7 (6%) (Scheme 2). This result shows that the reactive intermediate obtained by oxidation of 1 (which is believed to be fulvenyl radical 2) has several reactive sites. According to the experiments, reactivity is decreasing in the series C(7) > C(2)/C(3) > C(5) > C(1)/C(4) (Table 1), while simple frontier orbital considerations of radical 2 would suggest the sequence C(7) > C(5) > C(2)/C(3) > C(1)/C(4). The experimental result is in agreement with a considerable steric shielding of C(5) of 2.