A new and straightforward procedure is described for the preparation of highly substituted pyridines and pyridazines. The method involves a Diels-Alder/retro-Diels-Alder sequence leading to dihydropyridine or related intermediates, which can be aromatized to pyridines and pyridazines by treatment with silica gel. The value of this procedure has been demonstrated with a one-step -synthesis of an E-ring-modified
描述了一种新的、直接的方法来制备高度取代的吡啶和哒嗪。该方法涉及 Diels-Alder/retro-Diels-Alder 序列,导致二氢吡啶或相关中间体,可以通过硅胶处理将其芳构化为吡啶和哒嗪。该程序的价值已通过 E 环修饰的类固醇的一步合成得到证明。
Dienophilicity of Imidazole in Inverse Electron Demand Diels−Alder Reactions. 4. Intermolecular Reactions with 1,2,4-Triazines
作者:Brian R. Lahue、Zhao-Kui Wan、John K. Snyder
DOI:10.1021/jo030049y
日期:2003.5.1
cycloadditions of 2-substituted imidazoles with various 1,2,4-triazines produced both imidazo[4,5-c]pyridines (3-deazapurines) and pyrido[3,2-d]pyrimid-4-ones (8-deazapteridines). The product distribution was controlled by reactant substituents and influenced by reaction temperature. A regioselective method for the preparation of 6-unsubstituted 1,2,4-triazines was also developed. By using this route to 8-deazapteridines
Improved Methodologies for the Preparation of Highly Substituted Pyridines
作者:Yolanda Fernández Sainz、Steven A. Raw、Richard J. K. Taylor
DOI:10.1021/jo0518304
日期:2005.11.1
Two separate strategies have been developed for the preparation of highly substituted pyridines from 1,2,4-triazines via the inverse-electron-demand Diels−Alder reaction: a microwave-promoted, solvent-free procedure and a tethered imine-enamine (TIE) approach. Both routes avoid the need for a discrete aromatization step and offer significant advantages over the classical methods, giving a wide variety
Highly substituted pyridines via tethered imine–enamine (TIE) methodology
作者:Steven A. Raw、Richard J. K. Taylor
DOI:10.1039/b316107b
日期:——
A tethered imineâenamine methodology has been developed for the direct conversion of 1,2,4-triazines into highly substituted pyridines via the inverse electron demand DielsâAlder reaction which avoids the need for a discrete aromatisation step. This TIE methodology has also been applied in one pot reaction cascades involving 1,2,4-triazines and utilising MnO2-mediated tandem oxidation processes (TOPs).
一种束缚亚胺-烯胺方法已被开发出来,用于通过逆电子需求狄尔斯-阿尔德反应将 1,2,4-三嗪直接转化为高度取代的吡啶,从而避免了离散芳构化步骤的需要。这种 TIE 方法也已应用于涉及 1,2,4-三嗪并利用 MnO2 介导的串联氧化过程 (TOP) 的一锅反应级联中。
Development of a Mild and Versatile Directed Cycloaddition Approach to Pyridines
作者:Sylvestre P. J. T. Bachollet、Jérôme F. Vivat、Dean C. Cocker、Harry Adams、Joseph P. A. Harrity
DOI:10.1002/chem.201403916
日期:2014.9.26
The aza‐Diels–Alder cycloaddition of 1,2,4‐triazines with alkynes offers a rapid and convenient method for the synthesis of highly substituted pyridines, but often requires harsh conditions and long reaction times. The present study offers a solution to these limitations by use of a temporary tether established by a Lewis acid–base complexation of in situ generated alkynylboranes and triazines bearing
1,2,4-三嗪与炔烃的氮杂狄尔斯-阿尔德环加成反应为合成高度取代的吡啶提供了一种快速便捷的方法,但通常需要苛刻的条件和较长的反应时间。本研究通过使用原位生成的带有路易斯碱性供体的炔基硼烷和三嗪的路易斯酸碱络合建立的临时系链,为这些限制提供了解决方案。环加成反应在 40 °C 下 20 分钟内发生,可直接获得各种吡啶,并具有完整且可预测的区域控制。碳-硼键可以通过交叉偶联进一步官能化,从而允许在环加成后引入更多官能团。