Fluorinated pyrido(2,3-c)pyridazines. I. Reductive cyclization of ethyl 2-diazo-2-(5-fluoro-2-halonicotinoyl)acetate with trialkylphosphine.
作者:Teruyuki MIYAMOTO、Jun-ichi MATSUMOTO
DOI:10.1248/cpb.38.3211
日期:——
A new and convenient synthesis of 6-fluoro-4(1H)-oxopyrido[2, 3-c]pyridazine-3-carboxylate derizatives was achieved. One-pot reactions of ethyl 2-diazo-2-(6-chloro- and 6-tolylthio-5-fluoro-2-halonicotinoyl)acetates (9a and 9b, c) with tri-n-butylphosphine or tricyclohexylphosphine gave ethyl 7-chloro- and 7-tolylthio-6-fluoro-4(1H)-oxopyrido[2, 3-c]pyridazine-3-carboxylates (12a and 12b), respectively. The reaction of 9a-c with triphenylphosphine gave [1-ethoxycarbonyl-1-(6-chloro- and 6-tolylthio-5-fluoro-2-halonicotinoyl)methylene]hydrazono}triphenylphosphoranes (10a-c, R=Ph), which were hydrolyzed to the corresponding hydrazones 11a-c. Intramolecular cyclization of the hydrazones 11b and 11c furnished an alternative and efficient synthesis of 12b. Possible mechanisms for the reaction of 9 leading to 12 are discussed.
成功实现了一种新颖且便利的6-氟-4(1H)-氧基吡啶[2,3-c]吡嗪-3-羧酸酯衍生物的合成。将乙基2-二氮-2-(6-氯和6-甲苯硫基-5-氟-2-卤代烟酰基)醋酸酯 (9a 和 9b, c) 与三正丁基膦或三环己基膦在一锅反应中进行反应,分别生成乙基7-氯和7-甲苯硫基-6-氟-4(1H)-氧基吡啶[2,3-c]吡嗪-3-羧酸酯 (12a 和 12b)。将9a-c与三苯基膦反应生成[1-乙氧基羧酰-1-(6-氯和6-甲苯硫基-5-氟-2-卤代烟酰基)亚甲基]肼基}三苯基膦盐 (10a-c, R=Ph),随后水解得到相应的肼酮11a-c。肼酮11b和11c的分子内环化提供了一种替代的高效合成12b的方法。讨论了生成12的9反应的可能机制。