Stabilization of singlet ethoxycarbonylnitrene. Effect of dichloromethane on insertion into tetrahydrofuran and cyclohexane

Abstract

Ratios of singlet ethoxycarbonylnitrene to total nitrene species for the insertion of the nitrene into tetrahydrofuran and cyclohexane in dichloromethane were determined by taking into consideration tetrahydrofuran–dichloromethane interactions, solvent polarity effects, and triplet quenching experiments. In the case of the nitrene generated photochemically, the rations were almost independent of dichloromethane concentration. This probably suggests that singlet destabilization by the external heavy atom effect of dichloromethane is counterbalanced by singlet stabilization due to an interaction between the nitrene and the lone pair electrons of dichloromethane. Whereas the result for the insertion of the nitrene generated thermally reveals slightly predominant singlet destabilization compared with the photochemical case. This may also result from different temperature conditions.