Photoinduced Molecular Rearrangements. Some Investigations of the Photochemical Behavior of 3-(Acylamino)-1,2,5-Oxadiazoles (Furazans)

Article abstract of DOI:10.1021/jo00118a028

Mechanistic investigations of the photochemical behavior of some 3-(acylamino)-1,2,5-oxadiazoles (furazans) are reported.Irradiations of 3-(aroylamino)-4-methyl- and 3-(acetylamino)-4-phenyl-furazans at λ = 254 nm in methanol, and in methanol containing pyrrolidine, are considered.Photochemical processes follow different routes depending on the actual chromophore in the photoreaction.In the irradiation of 3-(aroylamino)-4-methylfurazans, two photochemical pathways involving a different multiplicity of excited states suggested: cleavage of the ring O(1)-N(5) bond via a singlet excited state (developing into nitrile oxides or carbodiimides, from which final products arise), or preliminary ring-closure involving the aroylamino group via a triplet excited state, respectively.In the irradiation of 3-(acetylamino)-4-phenylfurazan, photolytic intermediates arising from the cleavage of both the O(1)-N(2) and O(1)-N(5) bonds develop into the final products by reaction with the nucleophilic species present.