Photochemical Reactions of N-(Phenylalkyl, 2-pyridyl, or 2-pyridylmethyl)-o-sulfobenzoic Imides

Abstract

Photochemical reactions of N-(phenylalkyl, 2-pyridyl, or 2-pyridylmethyl)-o-sulfobenzoic imides 2-5 were examined in ethanol and benzene solutions. Irradiation in ethanol afforded benzamides 7, 9, 11, 14, and in benzene solution 2-phenylbenzamides 8, 10, 12, 15 were obtained. Irradiation of N-(2-pyridyl)-o-sulfobenzoic imide(5) generated benzo[c][1, 8]naphthyridin-6(5H)-one(13) as an additional product. This photocyclization was clarified to proceed via the S₁ state by the triplet quenching experiment. Those photochemical reactions were proposed to occur via a biradical formed by extrusion of SO₂. On ESR measurement of N-propyl-o-sulfobenzoic imide(1) irradiated in the methanol matrix at 15 K, the signals of a monoradical of g=2.0048 and a methyl radical were observed, but the existence of the biradical was not confirmed.