N-(2-Diazo-3-oxoalkanoyl)glycine esters. I. Synthesis of 4- and 5-phenoxyl derivatives and isomerization of N-(2-diazo-3-oxo-3-phenylpropanoyl)glycine ethyl ester

Abstract

A new preparative procedure for N-(diazoacetyl)glycine ethyl ester is described. The interaction of N-(diazoacetyl)glycine ethyl ester with four phenoxyacetyl chlorides gives the 4-phenoxylderivatives of N-(2-diazo-3-oxobutanoyl)glycine ethyl ester, and with β-(o-methoxyphenoxy)-propionyl chloride yields N-[2-diazo-3-oxo-5-(o-methoxyphenoxy)pentanoyl]glycine ethyl ester. A general chromatographic procedure for separating N-(2-diazo-3-oxoalkanoyl)glycine ethyl esters from N-(chloroacetyl)glycine ethyl ester has been developed. Crotonyl chloride reacts with a 1 mole excess of N-(diazoacetyl)glycine ethyl ester to form N-(2-diazo-3-oxo-4-hexenoyl)glycine ethyl ester, and with a 2 mole excess to form N-{2-diazo-3-oxo-3-[4′-methyl-5′(carboethoxymethyl)carbamoyl-Δ2pyrazolin-3′-yl]propanoyl}glycine ethyl ester, presumably by isomerization of an initially formed Δ1-pyrazoline derivative. The interaction of benzoyl and m-bromobenzoyl bromide with N-(diazoacetyl)glycine ethyl ester results initially in yellow oily products which, on the basis of spectral data, are the expected N-(2-diazo-3-oxo-3-rylpropanoyl)glycine ethyl esters. During chromatographic purification and (or) attempted crystallization, there occurs an isomerization to colorless crystalline products. The analytical and molecular weight data, together with the spectral evidence, support the tentative assignment of 1,2,3-triazole structures to the isomerization products. A spontaneous reverse Dimroth rearrangement is postulated.