Reactions of triarylarsines with nitrene precursors: formation of triarylarsinimines (AsAsAs-triarylarsine imides) and related compounds

Abstract

Copper catalysed or uncatalysed thermolyses of azides in triarylarsines provide good routes (40–90%) to the little known N-substituted triarylarsinimines (AsAsAs-triarylarsine imides)(Ar₃AsNX) including N-pentafluorophenyl-, N-4,6-dimethyl-2-pyrimidyl-, N-ethoxycarbonyl-, N-cyano-, N-p-tolysulphonyl-, and N-methylsulphonyl-triphenylarsinimines. Reaction of p-nitrophenyl azide with triphenylarsine and copper in boiling wet dioxan gave a monohydrate of the arsinimine [Ph₃As(OH)NHAr]. Benzoyl and p-nitrobenzoyl azides in the presence of triarylarsines underwent Curtius rearrangement rather than reaction to give the corresponding N-arylarsinimines which were instead obtained by copper catalysed thermolysis of the corresponding 3-aryl-1,4,2-dioxazolidin-5-ones with triphenylarsine. N-Ethoxycarbonyl- and N-p-tolysulphonyl-triphenylarsinimines were also obtained by base induced α-elimination from N-p-nitrophenylsulphonyloxy-urethane and -toluene-p-sulphonamide respectively. Circumstantial evidence is presented which suggests that triarylarsines are acting as nitrene traps in at least some of these reactions. The foregoing use of copper is recommended generally for lowering the temperature at which dioxazolidin-5-ones decompose to give aroylnitrenes.