ACID-INDUCED DIMERIZATION OF IMIDATES DERIVED FROM GLYCINE - SYNTHESIS OF METHYL N-(1,2,5-TRISUBSTITUTED-4-IMIDAZOYL)GLYCINATES

A number of N-(1,2,5-trisubstituted-4-imidazoyl)-glycinates 4 were pre pared in 60-95% yield from imidates 1 derived from alpha-amino esters by cyclodimerization without solvent at 70 degrees C in acetic acid me dium. According to this process, the reaction of imidate 1a as a 1,3-d ipole generated in situ by thermal 1,2-prototropy with the free ethyl benzimidate as the dipolarophile has been investigated for the first t ime and gave directly the methyl imidazole-4-carboxylate in moderate y ield by regioselective [3+2] cycloaddition. (C) 1996 John Wiley & Sons , Inc.