Reaction of anions from monoimines of benzil with alkylating agents. Photochemical reactivity of some 4-alkoxy-2-aza-1,3-dienes

Abstract

The reaction of benzil benzhydrylmonoimine 6a with methyl iodide or dimethyl sulphate as the electrophile affords 4-alkoxy-2-aza-1,3-dienes resulting from an O-alkylation. When benzyl chloride is employed, products of O-alkylation, C-alkylation and cyclization are produced, while with toluene-p-sulphonyl chloride only cyclization to a dihydro-oxazole takes place. Benzil α-phenylethylmonoimine 6b yields only products of C- and/or O-alkylation. In one case, when a large excess of dimethyl sulphate is used, cyclization affords N-methyl-2,3,5-triphenylpyrrole. Irradiation of the O-alkylated compounds (E)- and (Z)-4-methoxy-1,1,3,4-tetraphenyl-2-azabuta-1,3-diene and (E)-4-benzyloxy-1,1,3,4-tetraphenyl-2-azabuta,-1,3-diene in the presence of perchloric acid yields isoquinoline derivatives by a photo-Mannich reaction.