Substituent Effect at Aromatic Ring on the Thermal Denitrogenation of 7,7-Dialkoxy-1,4-diaryl-2,3-diazabicyclo[2.2.1]heptenes

Abstract

The thermal denitrogenation of azoalkanes (R-N=N-R) has attracted considerable attention from the mechanistic point of view. In general, the stepwise C-N bond cleavage is an accepted mechanism to rationalize experimental facts. We have investigated in this study the substituent and solvent effect on the thermal denitrogenation of azoalkanes that generates singlet ground-state cyclopentane-1,3-diyls. The obtained substituent and solvent effect can not be explained by the generally accepted stepwise-mechanism. The zwitterionic character of the singlet diradical is shown to be responsible for the unusual effects.