Visible light-sensitive properties of 1,2-dimethyl-2-(2-nitrophenyl)-2,3-dihydro-1H-perimidine

Four o- and p-nitro substituted 2-methyl-2-phenyl-2,3-dihydro-1H-perimidine derivatives were synthesized via a condensation–cyclization of naphthalene-1,8-diamine with nitro substituted acetophenones to study their photochemical properties. Only the o-nitrophenyl substituted perimidine 1 was found to be sensitive to light. When exposed to visible light under either aerobic conditions or argon atmosphere, it undergoes pyrimidine ring-opening/deoxygenation and pyrimidine oxidation to give the 2H-indazole 10 and perimidinone 11, respectively. A new visible light-sensitive o-nitrobenzylamino scaffold is introduced.