Synthesis and Tautomerism of Novel Quinoxalines (Part II)

Abstract

6-Chloro-3-methoxycarbonylmethylene-2-oxo-1,2,3,4-tetrahydroquinoxaline(5) 또는 3-methoxycarbonylmethylene- 6-nitro-2-oxo-1,2,3,4-tetrahydroquinoxaline(6)을 hydrazine hydrate와 반응시켜 3-hydrazinocarbonylmethylene-2-oxo-1,2,3,4-tetrahydroquinoxaline류(7, 8)를 합성하였다. 화합물 7 또는 8을 치환 벤즈알데히드류 및 헤테로고리 알데히드류와 반응시켜 quinoxaline류(9-14)를 각각 합성하였다. 합성한 화합물들은 dimethyl sulfoxide 용액에서 enamine형, methylene imine형 또는 enamine형, methylene imine형, enaminol형 사이에 토토머화 현상을 나타내었는데, 이들의 토토머 비를 1H NMR로서 측정하였다. The reaction of 6-chloro-3-methoxycarbonylmethylene-2-oxo-1,2,3,4-tetrahydroquinoxaline(5) or 3-methoxycarbonylmethylene-6-nitro-2-oxo-1,2,3,4-tetrahydroquinoxaline(6) with hydrazine hydrate gave 3-hydrazinocarbonylmethylene-2-oxo-1,2,3,4-tetrahydroquinoxalines(7, 8). The reaction of compound 7 or 8 with substituted benzaldehydes or heteroaromatic aldehydes afforded quinoxalines(9-14). Compounds showed the tautomerism between the enamine and methylene imine forms, and between the enamine, methylene imine and enaminol forms in dimethyl sulfoxide solution. The tautomer ratios were determined by the 1H NMR.