OXIDATIVE COUPLING OF 6,6-DIMETHYLPENTAFULVENYL ANION

Oxidative treatment of anion 11 (obtained by deprotonation of 6,6-dime thylpentafulvene 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 interm ediate obtained by oxidation of 11 (which is believed to be the fulven yl radical 12) has several reactive sites. According to the experiment s, 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 radical s 12 is the central effect governing regioselectivity and product dist ribution, while Coulomb and steric interactions are secondary effects (Table 4).