Switchable Synthesis of Pyrroles and Pyrazines via Rh(II)-Catalyzed Reaction of 1,2,3-Triazoles with Isoxazoles: Experimental and DFT Evidence for the 1,4-Diazahexatriene Intermediate
作者:Nikolai V. Rostovskii、Julia O. Ruvinskaya、Mikhail S. Novikov、Alexander F. Khlebnikov、Ilia A. Smetanin、Anastasiya V. Agafonova
DOI:10.1021/acs.joc.6b02389
日期:2017.1.6
According to the NMR and DFT investigations of the reaction mechanism, pyrroles and dihydropyrazines are formed, respectively, via 1,5- and 1,6-cyclization of common (5Z)-1,4-diazahexa-1,3,5-triene intermediates. The influence of the nature of the catalyst on the product distribution is rationalized in terms of the Rh-catalyzed isomerization of a pyrrolin-2-ylium-3-aminide zwitterion, the primary product
通过调节Rh(II)催化剂和反应条件,由5-烷氧基异恶唑和1-磺酰基-1,2,3-三唑合成了4-氨基吡咯-3-羧酸盐和吡嗪-2-羧酸盐。在100°C的Rh 2(OAc)4催化下于氯仿中的反应可提供高产率的4-氨基吡咯-3-羧酸酯。在回流的甲苯中使用Rh 2(Piv)4会形成1,2-二氢吡嗪-2-羧酸盐作为主要产物,可以通过一锅法将其加热至1,2-二氢吡嗪-2-羧酸盐。催化量的TsOH。根据对反应机理的NMR和DFT研究,吡咯和二氢吡嗪分别通过常见的(5 Z)-1,4-二氮杂六-1,3,5-三烯中间体。催化剂的性质对产物分布的影响通过吡咯烷-2-氨基-3-氨基两性离子的Rh催化的异构化而合理化,吡咯-2-烷基-3-氨基两性离子是1,4-二氮杂己三烯1,5-环化的主要产物。