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。
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