Bicyclic [<i>b</i>]-heteroannulated pyridazine derivatives.<b>4</b>. Cyclization reactions of 4-aryltetrahydropyridazine-3,6-dione 3-hydrazones with some keto esters
Ethoxycarbonylalkylidene derivatives 2 and 6 of the title hydrazones were obtained in the reaction with ethyl pyruvate or ethyl aroylformate and ethyl acetoacetate, respectively, in methanol. Both compounds were mixtures of geometric isomers with high predominance of one of them. Nmr spectroscopy revealed an unexpected magnetic non-equivalence of the CH2 protons in the ester ethyl group of the major
在甲醇中,分别与丙酮酸乙酯或芳酰基甲酸乙酯和乙酰乙酸乙酯反应,得到标题的乙氧基羰基亚烷基衍生物2和6。两种化合物都是几何异构体的混合物,其中之一占主导地位。Nmr光谱显示6个主要异构体的酯乙基中的CH 2质子具有意外的磁性非等价性。在惰性介质中加热(〜200°)或在乙醇乙醇钠2中回流时,环化成相应的哒嗪并[6,1- c ]-三嗪4,而6则形成吡唑基哒嗪7。通过X射线分析清楚地确定了后者的结构。在四丁基溴化铵的存在下,4a与苄基溴的烷基化选择性地在哒嗪N原子上发生。
Direct Pyridazine Ring Synthesis from<i>β</i>-Cyano Esters. A Facile Synthesis of the Derivatives of Tetrahydro-3,6-pyridazinedione 3-Hydrazone
Abstract 4-Substituted tetrahydro-3,6-pyridazinedione 3-hydrazones (2) (or their 3-hydrazino tautomers 3), useful intermediates in the synthesis of bicyclic pyridazinederivatives, were prepared in satisfactory yields in the reaction of the corresponding alkyl 3-substituted 3-cyanopropionates with hydrazine hydrate.