Carbonyl Activation by Selenium‐ and Tellurium‐Based Chalcogen Bonding in a Michael Addition Reaction
作者:Patrick Wonner、Tim Steinke、Lukas Vogel、Stefan M. Huber
DOI:10.1002/chem.201905057
日期:2020.1.27
Herein, we present the first use of tellurium‐based catalysts for the activation of a carbonyl compound (and only the second such activation by chalcogen bonding in general). As benchmark reaction, the Michael‐type addition between trans‐crotonophenone and 1‐methylindole (and its derivatives) was investigated in the presence of various catalyst candidates. Whereas non‐chalcogen‐bonding reference compounds
近年来,在非共价有机催化中使用硫族元素键(涉及亲电子硫族元素中心的非共价相互作用)引起了越来越多的兴趣,尤其是在分子间路易斯酸的使用方面。在本文中,我们介绍了碲基催化剂在羰基化合物活化中的首次使用(通常只有第二次通过硫族元素键的活化)。作为基准反应,反式之间的迈克尔型加法在各种候选催化剂的存在下研究了2-巴豆酮和1-甲基吲哚(及其衍生物)。非硫族元素键合的参考化合物没有活性,而基于三唑鎓的硫族元素双键供体可以实现高达1000的强速率加速,在2小时的反应时间内产品收率> 90%。有机碲衍生物明显比其硒和硫类似物具有更高的活性,非配位抗衡离子(如BAr F 4)提供了最强的阳离子催化剂。
Bromonium salts: diaryl-λ<sup>3</sup>-bromanes as halogen-bonding organocatalysts
Bromonium salts have been typically but infrequently used in various reactions as good leaving groups or as aryl or vinyl transfer reagents owing to their extremely high nucleofugality. Herein, we report the synthesis of novel, stable bromonium salts and their first catalytic application to the Michael reaction, with excellent product yield (up to 96%).
Michael Addition of Indoles to Enones Catalyzed by a Cationic Iron Salt
作者:Takashi Nishikata、Tsukasa Inishi、Goki Hirata
DOI:10.1055/s-0040-1705997
日期:2021.3
Indoles are one of the most valuable nucleophiles in Michaeladditionscatalyzed by a proper Lewis acid. In this paper, we found that a cationic iron salt is effective to carry out the Michaeladdition of indoles. β-Mono- and disubstituted enones reacted smoothly with indoles under our conditions. The cationic iron catalyst is very active, and the maximum TON was up to 425. Moreover, cationic iron-catalyzed