5-(trifluoromethyl) azafulvenium methide, intermediate that undergoes reaction through Unusual cycloaditions.

PELÁEZ, W. J.

Teresina, Piauí

Seminario; Seminario internacional invitado en el marco de los Programas de Pós-graduação em Farmacologia e em Ciências Farmacêuticas da Universidade Federal do Piauí.; 2014

Programas de Pós-graduação em Farmacologia e em Ciências Farmacêuticas da Universidade Federal do Piauí.

The generation and reactivity of a novel 1-methyl-5-trifluoromethyl-azafulvenium methide is described. Under microwave induced pyrolysis this intermediate could be trapped by dipolarophiles acting as a 4π as well as 8π dipole. Quantum chemical calculations carried out at the DFT level of theory allowed the rationalization of the results observed in the cycloaddition of 1-methyl-5-trifluoromethyl-azafulvenium methide with N-substituted maleimides. The study revealed that for 1,7-cycloadducts, the major products are obtained in trans- configuration from the unusual exo-cycloaddition mode, while for 1,3-cycloadducts, the cis-counterparts are obtained from this unexpected approach. In addition, under flash vacuum pyrolysis or conventional thermolysis 1-methyl-5-trifluoromethyl-azafulvenium methide undergoes an allowed suprafacial sigmatropic [1,8]H shift leading to the formation of 2-methyl-3-trifluoromethyl-1vinyl-1H-pyrrole. Keywords: Cycloadditions / Sigmatropic Shifts / Dipoles / Azafulvenium Methides / Trifluoromethylpyrroles / Flash Vacuum Pyrolysis / Microwave Chemistry / DFT calculations.