Trapping of cyclopropenyl radicals by 5,5-dimethyl-1-pyrroline-N-oxide

The possible generation of cyclopropenyl radicals by ultraviolet irradiatio n of different cyclopropenyl derivatives in fluid solution and in the prese nce of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as spin trap has been detect ed by electron paramagnetic resonance. The spectra consist of doublets of t riplets in which the beta-hydrogen splitting is larger than that of the nit rogen, in good agreement with data reported in the literature for other DMP O adducts. This methodology is unprecedented in the study of these transien t radical species, and these results suggest the participation of cycloprop enyl radicals in the photosensitized decarboxylation of N-(2-cyclopropenylc arbonyloxy)-phthalimides.