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Paper | Regular issue | Vol 63, No. 6, 2004, pp.1393-1408
Published online, 16th April, 2004
DOI: 10.3987/COM-04-10063
Synthesis, Properties, and Redox Ability of Optically Active 3-Carbamoyl-1,6-dimethylpyrimido[4,5-c]pyridazine-5,7(1H,6H)-dione and Related Pyrimido-annulated Pyridine Analogues

Shin-ichi Naya, Kohtaro Shibayama, and Makoto Nitta*

*Department of Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan

Abstract

Optically active 3-carbamoyl-1,6-dimethylpyrimido[4,5-c]pyridazine-5,7(1H,6H)-dione (13a) and related pyrimido-annulated pyridine analogues (13b,c) were prepared via the corresponding 3-ethoxycarbonyl-1,6-dimethylpyrimido[4,5-c]pydazine-5,7(1H,6H)-dione (11a) and the related compounds (11b,c). The properties of 11a-c, 13a-c, and the related 1,3,6-trimethylpyrimido[4,5-c]pyridazine-5,7(1H,6H)-dione (18a) as well as 7-phenyl- and 3,7,8-trimethyl-pyrido[2,3-d]pyrimidine-2,4(3H,8H)-dione (18b,c) having no carbamoyl or ester function were studied by the UV-VIS spectra and redox potentials. Although pyridazine derivative (13a) was not reduced, pyridine derivatives (11b,c), (13b), and (18b) were reduced by Na2S2O4 to give dihydrogenated compounds (20b,c), (21b), and (22b), respectively. The photo-induced oxidation reactions of 13a,b and 18a-c toward some amines under aerobic conditions were studied to give the corresponding imines in more than 100% yields [based on compounds 13a,b and 18a-c], suggesting that the oxidation proceeds in an autorecycling process.