Reaction Mechanism and Regioselectivity of the Bingel-Hirsch Addition of Dimethyl Bromomalonate to La@C2v-C82

Abstract

We quantum chemically explore the thermodynamics and kinetics of all 65 possible mechanistic pathways of the Bingel-Hirsch addition of dimethyl bromomalonate to the endohedral metallofullerene La@C2v-C82 that result from the combination of 24 nonequivalent carbon atoms and 35 different bonds present in La@C2v-C82 by using dispersion-corrected DFT calculations. Experimentally, this reaction leads to four singly bonded derivatives and one fulleroid adduct. Of these five products, only the singly bonded derivative on C23 could be experimentally identified unambiguously. Our calculations show that La@C2v-C82 is not particularly regioselective under Bingel-Hirsch conditions. From the obtained results, however, it is possible to make a tentative assignment of the products observed experimentally. We propose that the observed fulleroid adduct results from the attack at bond 19 and that the singly bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely. Fulleroid formation: Five experimentally observed but hitherto uncharacterized products in the Bingel-Hirsch (BH) addition of dimethyl bromomalonate to La@C2v-C82 were identified quantum chemically, only one of which is a fulleroid (see figure; white: C, dark red: La, green: Br, red: O, blue: H). Computational exploration also shows that the Bingel-Hirsch addition to La@C2v-C82 is not particularly regioselective, so at least ten products are expected, even under mild reaction conditions