Trapping of Cyclopropenyl Radicals by 5,5-Dimethyl-1-pyrroline-N-oxide

The possible generation of cyclopropenyl radicals by ultraviolet irradiation of different cyclopropenyl derivatives in fluid solution and in the presence of 5,5-dimethyl-1-pyrroline- N -oxide (DMPO) as spin trap has been detected by electron paramagnetic resonance. The spectra consist of doublets of triplets in which the β-hydrogen splitting is larger than that of the nitrogen, in good agreement with data reported in the literature for other DMPO adducts.This methodology is unprecedented in the study of these transient radical species, and these results suggest the participation of cyclopropenyl radicals in the photosensitized decarboxylation of N -(2-cyclopropenylcarbonyloxy)phthalimides.