Synthesis of Ethyl Pyrimidine-4-carboxylates from Unsymmetrical Enamino Diketones and Their Application in the First Synthesis of Pyrimido[4,5-<i>d</i>]pyridazin-8(7<i>H</i>)-ones
作者:Marcos Martins、Fernanda Rosa、Pablo Machado、Gabriela Fiss、Pâmela Vargas、Tanize Fernandes、Helio Bonacorso、Nilo Zanatta
DOI:10.1055/s-0028-1083202
日期:2008.11
The reaction of unsymmetrical enamino diketones [RC(O)C(=CNMe2)C(O)CO2Et, where R = Ph, 4-MeC6H4, 4-MeOC6H4, 4-BrC6H4, 4-ClC6H4, 4-FC6H4, 4-O2NC6H4, 2-thienyl, benzofuran-2-yl, and CF3] with N-C-N dinucleophiles, such as benzamidine hydrochloride or 1H-pyrazole-1-carboxamidine monohydrochloride, afforded a series of ethyl 2,5-disubstituted pyrimidine-4-carboxylates in a chemoselective and highly chemoselective manner (51-86%). Reaction of these two series of pyrimidines (R = Ph, 4-MeOC6H4, 4-FC6H4, and 2-thienyl) with hydrazine monohydrate under mild conditions led to 2,5-substituted pyrimido[4,5-d]pyridazin-8(7H)-ones in high yields (81-92%).
不对称烯氨基二酮[RC(O)C(=CNMe2)C(O)CO2Et,其中 R = Ph、4-MeC6H4、4-MeOC6H4、4-BrC6H4、4-ClC6H4、4-FC6H4、4-O2NC6H4、2-噻吩基、苯并呋喃-2-基和 CF3]与 N-C-N 二亲核物的反应、如苯甲脒盐酸盐或 1H-吡唑-1-甲脒单盐酸盐,以化学选择性和高化学选择性的方式(51-86%)得到一系列 2,5-二取代的嘧啶-4-甲酸乙酯。在温和的条件下,将这两个系列的嘧啶(R = Ph、4-MeOC6H4、4-FC6H4 和 2-噻吩基)与一水合肼反应,可以高产率(81-92%)得到 2,5-取代的嘧啶并[4,5-d]哒嗪-8(7H)-酮。