Preparation of 2-phenyl-2-hydroxymethyl-4-oxo-1,2,3,4-tetrahydroquinazoline and 2-methyl-4-oxo-3,4-dihydroquinazoline derivatives formation

The cyclization of phenacyl anthranilate has been studied with the aim to d evelop the synthesis of 2-(2'-aminophenyl)-4-phenyloxazole. However, a diff erent course of the reaction than expected was observed. 2-Phenyl-2-hydroxy methyl-4-oxo-1,2,3,4-tetrahydroquinazole (3a) was formed by the reaction of phenacyl anthranilate (2) with ammonium acetate under various conditions. 3-Hydroxy-2-phenyl-4(1H)-quinolinone (4) arose by heating compound 3a in ac etic acid. The same compound was obtained by melting compound 3a, but the y ield was lower. Different types of Products resulted in the reaction of compound 3a with ac etic anhydride. Under mild conditions acetylated products 2-acetoxymethyl-2 -phenyl-4-oxo-1,2,3,4-tetrahydroquinazoline (7a) and 2-acetoxymethyl-3-acet yl-2-phenyl-4-oxo- 1,2,3,4-tetrahydroquinazoline (8) were prepared. If the reaction was carried out under reflux of the reaction mixture, molecular re arrangement took place to give cis and trans 2-methyl-4-oxo-3-(1-phenyl-2-a cetoxy)vinyl-3,4dihydroquinazolines (9a and 9b). All prepared compounds hav e been characterised by their H-1, C-13 and N-15 NMR spectra, IR spectra an d MS.