Annulation of pyridinium rings onto nitrogen heterocycles
Annulation of pyridinium rings onto nitrogen heterocycles
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DOI：
10.1021/jo00434a028
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发表时间：
1977-07
影响因子：
3.6
通讯作者：
D. D. Chapman-D.;J. K. Elwood;D. W. Heseltine;H. Hess;D. Kurtz
中科院分区：
文献类型：
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作者：
D. D. Chapman-D.;J. K. Elwood;D. W. Heseltine;H. Hess;D. Kurtz
在初步交流中，我们描述了一种通过质子化杂环与甲基乙烯基酮反应合成稠合吡啶鎓盐的简单方法。在本文中，我们报告了该方法扩展到其他杂环和不饱和酮。该合成的第一个例子1是根据方案I制备3-甲基-4-苯基吡啶并[2, 1-5]苯并噻唑溴化物(4)。2-苄基苯并噻唑溴化物(1)与乙腈中的甲基乙烯基酮(MVK)进行迈克尔加成得到加合物2。以前已经报道过这种类型与其他氮杂环碱的盐的加成。 2’3产物2通过IR、NMR谱和元素分析进行了表征。在多种溶剂中加热2导致活性亚甲基和羰基闭环，得到二氢吡啶并苯并噻唑鎓盐3。该化合物的NMR谱(Me2SO-d6)显示在2.03处有一个甲基以及以3.18和4.85为中心的两个亚甲基三联体。 3至4的芳构化可以通过多种方式进行，例如，在DMA或Me 2 SO中长时间加热，但最容易通过在DMA中与Pd/C一起加热。 NMR 谱 (Me2SO-d6) 或 4 中的特征峰是 2.53 处的甲基和 10.24 处的单个质子双峰，归属于位置 1 的氢。
In a preliminary communication1 we described a simple method for the synthesis of fused pyridinium salts by the re-action of protonated heterocycles with methyl vinyl ketone. In this paper we report the extension of this method to other heterocycles and unsaturated ketones. The first example of this synthesis1 was the preparation of 3-methyl-4-phenylpyrido [2, l-5] benzothiazolium bromide (4) according to Scheme I. The formal Michael addition of 2-benzylbenzothiazolium bromide (1) to methyl vinyl ketone (MVK) inacetonitrile gave the adduct 2. Additions of this type to salts of other nitrogen heterocyclic bases have been reported previously. 2’3 Product 2 was characterized by its IR, NMR spectra, and elemental analysis. Heating 2 in a variety of solvents caused ring closure of the active methylene and the carbonyl group to give the dihydropyridobenzothiazolium salt 3. The NMR spectrum (Me2SO-d6) of this compoundshowed a methyl group at 2.03 and two methylene triplets centered at 3.18 and 4.85. The aromatization of 3 to 4 could be carried out in a variety of ways, eg, prolongedheating in DMA or Me2SO, but most easily by heating with Pd/C in DMA. Characteristic peaks in the NMR spectrum (Me2SO-d6) or 4 were a methyl group at 2.53 and a single proton doublet at 10.24 assigned to the hydrogen at position 1.