Photochemical reaction of 2,4-dinitrodiphenylacetamide and related compounds: spectroscopic and chemical identification of intermediates

Abstract

2,4′-Dinitrodiphenylacetamide 1b reacts via the triplet state to give 3-nitrophenazine 5-oxide 2b. The initial step is addition of the nitro group to the CO bond. This intermediate 7 rearranges in the ms time scale to yield an O-acylnitro derivative 8. This, in turn, undergoes heterolytic cleavage (rate dependent upon solvent polarity) and the aminium cation thus formed cyclizes to 2b. Intermediate 7 is sensitive to acid-catalysed hydrolysis, and the cleavage of 8 and subsequent cyclization are influenced by various additives. Thus, with triphenylphosphine a phosphoranylidenamino derivative is obtained, and 2,6-di-tert-butylphenol gives 4-nitro-2-nitrosodiphenylamine. Two other amides are compared.