Triphenylmethyl phenylcyanomethylenenitronate: formation and thermolysis

Abstract

The previously reported formation of carbon dioxide, α,α′-bis(trityl)stilbene (4), benzonitrile N-oxide (5), trityl isocyanate (6), and C₃₃H₂₅N₃₀(11) from a mixture of trityl chloride and silver phenylcyanomethylenenitronate in toluene is now attributed to the initial formation at –20 °C of trityl phenylcyanomethylenenitronate (3) and its dissociations at 5 °C. The ester (3) was characterized by conversion into bromonitrophenylacetonitrile (7) by treatment with bromine, to p-nitrobenzoyl cyanide (8) by treatment with dinitrogen tetraoxide, to trityl alcohol by hydrolysis, and to a mixture of trityl alcohol and trityl peroxide by exposure to the atmosphere. The bisazostilbene (4)(18%) and C₃₃H₂₆N₃₀, identified by X-ray crystallographic analysis to be 4,5-diphenyl-1-triphenylmethoxy-1,2,3-triazole (11)(24%), were obtained from the nitronate ester (3) in toluene at 5 °C; the nitrile oxide (5) and the isocyanate (6) were obtained in low yields from the ester (3) in dimethyl sulphoxide at 25 °C. Hydrolysis converted the triazole (11) into 1-hydroxy-4,5-diphenyl-1,2,3-triazole (12) and trityl alcohol. Silver p-bromophenylcyanomethylenenitronate and trityl chloride afforded α,α′-bis-(tritylazo)-p,p′-dibromostilbene and its thermolysis product, p,p′-dibromodiphenylacetylene. Fragmentation of the ester (3) in the presence of added phenyl isocyanate gave the bisazo compound (4) and 3,4-diphenyl-1,2,4-oxadiazol-5-one (18). A similar mixture stored at –20 °C gave the triazole (11) and the oxadiazolone (18). Aroyl nitrile oxides as well as phenyl isocyanate suppressed the formation of the red bisazostilbene (4). The intermediacy of the N-trityl imine (14) of 4H-3-phenyl-1,2-oxazet-4-one 2-oxide in the thermolysis of the nitronate (3) was discussed.