Regioselective Electrochemical Hydroalkylations of [60]Fullerene-Fused Furochromenone

Regioselective electrochemical hydroalkylations of [60]fullerene-fused furochromenone with alky halides under different acidic conditions unexpectedly afford three types of tetra-functionalized [60]fullerene derivatives in high yields. When acetic acid is used as the proton source, two 1,2,3,4-adducts with retained or rearranged five-membered heterocycle are obtained as major and minor products, respectively. While trifluoroacetic acid is employed as the proton source, 1,2,3,16-adducts and 1,2,3,4-adducts, both with the five-membered heterocycle rearranged from [6,6]-junction to [5,6]-junction, are generated. Intriguingly, the obtained 1,2,3,16-adducts can be transformed into 1,2,3,4-adducts accompanied by rearrangement of the fused five-membered heterocycle from [5,6]-junction to [6,6]-junction. These products have been characterized by spectroscopic data and single-crystal X-ray analysis. Moreover, the two 1,2,3,4-adducts with the heterocycle fused to [5,6]-junction or [6,6]-junction show diagnostic UV-vis spectra, which may be useful for the identification of these two types of 1,2,3,4-adducts in the future. A plausible reaction mechanism has been proposed to elucidate the formation of hydroalkylation products in the presence of different acids.