Open-chain nitrogen compounds. Part IV. Synthesis of 5-hydroxy-1,2,3-triazoles from 1-aryl-3-(ethoxycarbonylmethyl)triazenes: a new route to α-diazo-N-arylacetamides

Abstract

A series of triazenes of type ArN=N—NH—CH2CO2Et, N-arylazoglycinc ethyl esters, have been prepared by coupling the arene diazonium salt, ArN2+•X−, with ethyl glycinate, NH2CH2CO2Et; an electron-withdrawing substituent, e.g. NO2, CN, CO2R, and Cl, in the ortho or para position of the aryl group is essential for efficient coupling. The p-substituted arylazoglycine ethyl esters cyclize when treated with alcoholic potassium hydroxide to afford the potassium salts of the 1-aryl-5-hydroxy-1,2,3-triazoles, which can be obtained free by acidification of the potassium salt solution with acetic acid. Reaction of the potassium salts with acetic anhydride yields the 1-aryl-5-acetoxy-1,2,3-triazoles. The5-hydroxytriazoles, when heated in ethanol, rearrange to α-diazoacetanilides, ArNH•COCHN2. The diazoamides can be obtained in low yield directly from the triazenes by prolonged refluxing in ethanol. o-Substituted aryltriazenes do not cyclize under the same conditions but fragment to the arylamine.