Synthesis of N-amino-3-hydroxy-2-phenyl-4(1H)-quinolinone

摘要

2-[(Disubstituted-methylene)-hydrazino] benzoic acid phenacylesters 2a - 2d, prepared from anthranilic acid phenacylester 1, were unsuccesfully tried as starting materials for the synthesis of N-amino-3-hydroxy-2-phenyl-4(1H)-quinolinone 8. The desired compound 8 was prepared by cyclization of N-acetyl as well as N-benzoyl-hydrazinobenzoic acid phenacylester 6a or 6b in polyphosphoric acid to afford N-acylamino-3-hydroxy-2-phenyl-4(1H)-quinolinone 7a or 7b, respectively. Surprisingly, the acyl group was resistant to attack by both hydrochloric acid as well as sodium hydroxide solution. It could be removed by boiling the compounds 7a or 7b respectively in 50% sulphuric acid to afford the the target compound 8.