THEORETICAL STUDIES ON THE FORMATION MECHANISM AND STRUCTURE OF PENTAFULVENONE AND AZAFULVENONE

Abstract

The formation mechanisms of pentafulvenone and azafulvenone were extensively investigated at the B3LYP/6-311++G** level and the potential energy surfaces were drawn out. Ketene pentafulvenone (A) and 3-carbonyl-3H-pyrrole (C) can be formed by eliminating N 2 from the diazo ketone via α elimination reaction and ketene 2-carbonyl-2H-pyrrole (B), 4-carbonyl-4H-imidazole (D), and 2-carbonyl-2H-imidazole (E) were formed by the elimination of water or methanol from pyrrole-2-carboxylic acid (rB) and carboxylate (rD and rE) via β elimination reaction. The structures of these monomers were compared and showed some information about the bond changed characters. The structure investigation indicated that the C = C bond is activated when the nitrogen atom locates in the ortho position of the C = C = O part, and therefore ortho-monomers are more facile to react. The difference of the amount and stability of the corresponding dimers are caused by differing the position and number of nitrogen atom and the variety of the ortho-dimer is complicated. In addition, the infrared spectra of the title species were also analyzed including the vibrational frequencies, IR relative intensities, and vibrational mode assignment.