In this article, the selective synthesis of 4-iso-butoy-10-hydroxy-1,7-phenanthroline-2,8-dicar- boxylic acid dimethyl ester (1) was reported. Compound 1 was synthesized via three steps from m-phenylenedi- amine (3). Reaction of m-phenylenediamine and dimethyl acetyleneducarboxylate (4) yielded 1,3-bis-(1,2-di-methoxycarbonyl-vinylamino)benzene (5), which was refluxed in diphenyl ether to yield 4,10-dihydroxy-1,7-phenanthroline-2,8-dicarboxylic acid dimethyl ester (6) and 4,5-dihydroxy- 1,8-diaza anthracene-2,7-dicarboxylic acid dimethyl ester (7). The yield of 6 was about 7～9 times higher than that of 7, estimated from the ¹H NMR spectrum. The mixture of 6 and 7 was then converted into 1 and 4,5-di-iso-butoy-1,8-diaza anthracene-2,7-dicarboxylic acid dimethyl ester (2) via Mitsunobu reaction. The purified yield of 1 was about 5～7 times of that of 2. Crystal structure of compound 1 revealed formation of a six-member intramolecular hydrogen-bond between the 10-hydroxyl-hydrogen atom and 1-nitrogen atom, while no intramolecular hydrogen-bonds can be formed in molecule 2. This strongly suggested a deep relationship between formation of the hydrogen bond and synthetic selectivity.

Key words: synthetic selectivity, intramolecular hydrogen-bond, Mitsunobu reaction, crystal structure