关键词: 缩合, 不对称1,2-二酮, 同分异构体, 1,2,4-三嗪

This paper reports the selective condensation of aminoguanidine with 1-(1-ethyl-1H-indol-5-yl)-2-phenylethane- 1,2-dione to afford 1,2,4-triazines. The constituents and relative proportion of these condensation products are identified by the methods of target-oriented synthesis and nuclear magnetic resonance. And the influences on the relative proportion by different substituents are described. When the phenyl is substituted with the electron-withdrawing group, the ratio of the isomers 6-(1-ethyl-1H-indol-5-yl)-5-phenyl-1,2,4-triazin-3-amine/5-(1-ethyl-1H-indol-5-yl)-6-phenyl-1,2,4-triazin-3-amine [n(2a):n(4a)] is 40:60; when without the substituent, the ratio of the isomers 6-(1-ethyl-1H-indol-5-yl)-5-(4-nitrophenyl)- 1,2,4-triazin-3-amine/5-(1-ethyl-1H-indol-5-yl)-6-(4-nitrophenyl)-1,2,4-triazin-3-amine [n(2b):n(4b)] is 63:37; when substituted with the electron-donating group, the type of the major products was 2.

Key words: condensation, unsymmetrical 1,2-diketone, isomer, 1,2,4-triazine