New transformations of the reaction product of 4-(dichloromethylene)-2-phenyl-1,3-oxazol-5(4H)-one with triphenylphosphine

Consecutive treatment of the available 4-(dichloromethylene)-4-phenyl-1,3-oxazol-5(4H)-one with triphenylphosphine, water, and triethylamine gives a stabilized ylide Ph3P=CHCONHCOPh. Its structure was proved by X-ray diffraction. The ylide reacts with hydrogen chloride and phosphorus pentachloride to give a many-center phosphonium reagent with a 1,3-dichloro-2-aza-1,3-diene group, which enters cyclocondensations with hydrazine hydrate, phenylhydrazine, and benzamidine. These reactions allowed synthesis of phosphonium salts of the general formula Ph3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\mathop P\limits^ +$$ \end{document}CH2HtAn− derived from 1,2,4-triazole or 1,3,5-triazine. The structure of the cyclization products was established by spectral methods, as well as by alkaline dephosphorylation.