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

A series of ethyl 2‐oxo‐3(2 H )‐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 3 H ‐2‐oxoimidazo[2,1‐ b ]benzoxazole derivatives 9 . Ethyl 2‐oxo‐3(2 H )‐benzoxazolepropionate ( 10 ) was prepared by a Michaël reaction of ethyl acrylate with 2‐benzoxazolone ( 1a ). With 10 , no cyclic transformation was observed in the presence of ammonia or alkylamine.