Reactions of co-ordinated ligands. Part IV. The use of aminomagnesium compounds in the preparation of α-amino-acid amides from α-amino-acid ethyl esters

Abstract

The action of benzylamine and magnesium methoxide on the Schiff bases formed from glycine ethyl ester and salicylaldehyde, 2-hydroxy-1-naphthaldehyde, and pentane-2,4-dione results in benzyl amide formation and, in the case of the first two Schiff bases, amine-exchange. It is suggested that the benzyl amide formation occurs by means of chelates which involve the Schiff bases and an aminomagnesium compound. An analogous explanation is offered to account for the large variation in the yields of benzyl amides obtained when various ethyl esters are heated with benzylaminomagnesium iodide and benzylaminozinc iodide. Treatment of the Schiff bases formed from α-amino-acid ethyl esters and either pentane-2,4-dione or 1-phenylpropane-1,3-dione with the ethyl(amino)magnesium compounds prepared by addition of primary or secondary amines to diethylmagnesium affords good yields of the expected Schiff base amides. The parent α-amino-amides can be obtained (as hydrohalides) from these by hydrolysis with hydrochloric acid or by treatment with bromine water.