ИСТИНА

Trifluoromethylated derivatives of fullerenes C60 and C70 are of the particular interest as promising materials for construction of organoelectronic devices due to their enhanced electron affinity, chemical stability and ability to undergo multiple reversible electrochemical reductions. It was found, that specific arrangement of CF3 addends governs electronic affinities of the isomeric molecules in range of 0.5 eV [1]. Furthermore, it has been shown recently, that near-equatorial arrangement of eight CF3 groups in Cs-symmetrical C70(CF3)8 provides regioselectivity to a number of reactions of its further functionalization. The sterical unhindered chlorination [2] and cyanation [1] of Cs-C70(CF3)8 proceeds selectively at its near-equatorial [5,6]-double bond while nucleophilic addition of the bulky diethyl bromomalonate carbanion results in cycloproponation at more sterically accessible [6,6]-bonds at the poles of the fullerene cage [3]. Thus, functionalization of trifluoromethylated fullerenes is promising approach to achieve predetermined regiochemistry and, consequently, required chemical and electronic properties. Here we reports the results of the nucleophilic cycloproponation of C2-symmetrical C70(CF3)8 by the Bingel reaction and its modification due to Hirsch (aka Bingle-Hirsch reaction). The Bingel reaction regioselectively occurs at near-polar regions yielding isomeric-pure C70(CF3)8[C(CO2Et)2] monoadduct and C2-C70(CF3)[C(CO2Et)2]2 bisadduct. Unexpectedly, the Bingle-Hirsch reaction, apart from compounds mentioned above, affords alkylation at near-equatorial site resulting in C70(CF3)8[CH(CO2Et)2]H. The structures of compounds obtained were unequivocally determined by means of 1H and 19F NMR spectroscopy and X-Ray single crystal data. The unexpected influence of the addition pattern in C2-C70(CF3)8 to such regioselectivity of the studied reactions are interpreted by means of quantum chemical calculation performed at the DFT level of the theory.