Oxidative Coupling of 6,6‐Dimethylpentafulvenyl Anion

Abstract

Oxidative treatment of anion 11 (obtained by deprotonation of 6,6‐dimethylpentafulvene 10, Scheme 3) with CuCl2 gives a very complex mixture of coupling products 13 (18%), 14 (16%), 15 (36%), 16 (5%), and 17 (6%) (Scheme 4 and Table 2). These results show that the reactive intermediate obtained by oxidation of 11 (which is believed to be the fulvenyl radical 12) 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 2), while simple frontier‐orbital considerations would suggest the sequence C(7) > C(5) > C(2)/C(3) > C(1)/C(4). The results suggest that SOMO‐SOMO interaction of the approaching fulvenyl radicals 12 is the central effect governing regioselectivity and product distribution, while Coulomb and steric interactions are secondary effects (Table 4).