Reaction of 2,4-dinitrophenylhydrazones of triphenyl(2-aroylethyl)phosphonium bromides with aqueous alkali and some transformations of the betaines formed

Abstract

Triphenyl(2-p-toluoylethyl)- and triphenyl(2-p-bromobenzoylethyl)phosphonium bromide 2,4-dinitrophenylhydrazones were established to form a bipolar compounds with a negatively charged nitrogen atom and a positively charged phosphonium atom, under the action of aqueous alkali at 0°C. When refluxed in acetonitrile, the product formed from triphenyl(2-p-toluoylethyl)phosphonium bromide undergoes cleavage by a five-membered ring mechanism to give triphenylphosphine and tolyl vinyl ketone 2,4-dinitrophenylhydrazone. The reactions of the above betains with methyl iodide give rise to N-alkylation and cleavage products, but, in addition, iodide analogs of the starting phosphonium salt 2,4-dinitrophenylhydrazones which are probably formed via N→C negative charge transfer, C-methylation, and reaction of the resulting products with N-betaines.