Synthesis of 1-(2-hydroxyphenyl)-2,4-imidazolidinedione derivatives through cyclic transformations of ethyl 2-oxo-3(2H)-benzoxazoleacetate derivatives

A series of ethyl 2-oxo-3(2H)-benzoxazoleacetate derivatives 2 have been synthesized. By reaction with ammonia, primary amines or hydrazine, these compounds 2 were transformed into 1-(2-hydroxyphenyl)-2,4-imidazolidinedione derivatives 4, 5 and 6, respectively. Some of these new hydantoins 4, treated with phosphorus oxychloride, gave 3H-2-oxoimidazo[2,1-b]benzoxazole derivatives 9. Ethyl 2-oxo-3(2H)-benzoxazolepropionate (10) was prepared by a Michael reaction of ethyl acrylate with 2-benzoxazolone (1a). With 10, no cyclic transformation was observed in the presence of ammonia or alkylamine.