Fused 1, 3-Oxazine Derivatives. Synthesis of 2H-1, 3-Oxazino [5, 6-b]-quinoxaline-2, 4 (3H)-diones (1-Oxaalloxazines), 2H-1, 3-Oxazino-[6, 5-b] quinoline-2, 4 (3H)-diones (5-Deaza-1-oxaalloxazines), and 2H-Pyrido [3, 2-e]-1, 3-oxazine-2, 4 (3H)-diones

Abstract

Reactions of 6-anilino-3-methyl-2H-1, 3-oxazine-2, 4 (3H)-diones (1) with triethyl orthoformate, N, N-dimethylformamide dimethyl acetal, diethyl azodicarboxylate, and dimethyl acetylene-dicarboxylate were carried out with the aim of synthesizing fused-ring 1, 3-oxazine derivatives 3-Methyl-2H-1, 3-oxazino [6, 5-b] quinoline-2, 4 (3H)-dione (3-methyl-5-deaza-1-oxaalloxazine) (2) and 3-methyl-2H-1, 3-oxazino [5, 6-b] quinoxaline-2, 4 (3H)-dione (3-methyl-1-oxaalloxazine) (8) were obtained by the reactions of the 6-anilinooxazine (1a) with triethyl orthoformate and diethyl azodicarboxylate, respectively. Treatment of 1a with dimethyl acetylenedicarboxylate gave methyl 3-methyl-2, 4, 7-trioxo-8-phenyl-3, 4, 7, 8-tetrahydro-2H-pyrido [3, 2-e]-1, 3-oxazine-5-carboxylate (9a) as well as methyl 1-methyl-2, 5-dioxo-1, 2, 5, 10-tetrahydrobenzo [b] [1, 8] naphthyridine-4-carboxylate (10) as a ring transformation product. The 6-(p-anisidino)-(1b) and the 6-(3, 4-xylidino)-oxazine (1c) also gave the corresponding pyrido [3, 2-e]-1, 3-oxazines (9b) and (9c).