PHOTOCHEMISTRY OF NITROGEN-HETEROCYCLES .5. PHOTOSUBSTITUTION REACTION IN HETEROCYCLIC SERIES - CASE OF 1-PARA-NITROPHENYLPYRAZOLE AND 1-PARA-NITROPHENYLIMIDAZOLE

The photosubstitution reactions of eight 1-p-nitrophenylpyrazoles and two 1-p-nitrophenylimidazoles bearing different substituents in the heterocyclic ring have been studied. In the case of pyrazole derivatives, among the different nucleophiles utilized, only the acetate, cyanate and cyanide ions gave identifiable products. The two first ones lead to the 4-formyl derivative of the starting material. With the cyanide ion the reaction is more complicated, not only the 4-cyano derivative is formed but also the 4-carboxamido and several reduced products: p-amino, p-formamido, p-acetamido, p-carbamate and p-azoxypheny 1-1 pyrazoles. In the case of 1-p-nitrophenylimidazoles, the only interesting results have been obtained with the cyanide ion: formation of cyano- and hydroxymethylene-imidazoles. © 1979.