J. Bergman et C. Stalhandske, CYCLIZATION OF N-ACYLANTHRANILIC ACIDS WITH VILSMEIER REAGENTS - CHEMICAL AND STRUCTURAL STUDIES, Tetrahedron, 52(3), 1996, pp. 753-770
Vilsmeier reagents, generated from e.g. N, N-dimethylformamide and oxa
lyl chloride, react with N-acetylanthranilic acid to produce the -(2'-
dimethylamino)ethenyl-4H-3,1-benzoxazin-4-one 13a.. N-phenylacetylanth
ranilic acid similarly gave 2-(2'-dimethylamino-1'-phenyl)ethenyl-4H-3
, 1-benzoxazin-4-one 6a, whose structure has been determined by X-ray
crystallography. The benzoxazinone 6a could readily be converted to fu
sed heterocyclic systems, thus e.g. 13a and hydrazine hydrate gave pyr
azolo[5,1-b]-4H-quinazoline 20a. Reaction of N-acetylated anthranilic
acids and oxalyl chloride alone gave the fused oxazolidine-4,5-diones
24. The structure of one representative, 24a, was established by X-ray
crystallography. Thermolysis of 24a gave, after elimination of CO+CO2
, 2-benzyl-4H-3,1-benzoxazin-4-one 7 in quantitative yield.