We present a new class of catalysts based on the combination of N,N'-diaryl(thio)ureas and weak silicon Lewis acids (e.g., SiCl(4)). Such silicon-(thio)urea catalysts effectively catalyze the stereospecific rearrangement of epoxides to quaternary carbaldehydes.
Synthetic Studies toward Aryl-(4-aryl-4<i>H</i>-[1,2,4]triazole-3-yl)-amine from 1,3-Diarylthiourea as Urea Mimetics
作者:Amarnath Natarajan、Yuhong Guo、Haribabu Arthanari、Gerhard Wagner、Jose A. Halperin、Michael Chorev
DOI:10.1021/jo0508189
日期:2005.8.1
4]triazole-3-yl-amines as urea mimetics from the corresponding 1,3-disubstituted thioureas has been studied, and the scope and limitations of this reaction are presented. The reaction proceeds through the formation of a carbodiimide, followed by a sequential addition−dehydration with acyl hydrazides. 1,3-Branched dialkylthioureas result in the formation of the corresponding ureas. The electronic and steric
Cooperative organocatalysis of Mukaiyama-type aldol reactions by thioureas and nitro compounds
作者:Konstantin V. Bukhryakov、Victor G. Desyatkin、Valentin O. Rodionov
DOI:10.1039/c6cc01984f
日期:——
A unique organocatalytic system for Mukaiyama-type aldol reactions based on the cooperative action of nitrocompounds and thioureas has been identified. This system is compatible with a wide range of...
Lewis Base Catalysis by Thiourea: <i>N</i>-Bromosuccinimide-Mediated Oxidation of Alcohols
作者:Chandra Bhushan Tripathi、Santanu Mukherjee
DOI:10.1021/jo202269p
日期:2012.2.3
In recent times, (thio)ureaderivatives have become synonymous with hydrogenbonding owing to their extensive applicability as small molecule organocatalysts. In this paper, another activation mode by thiourea derivatives, namely via Lewis base catalysis, is disclosed for the NBS-mediated oxidation of alcohols. The mild reaction conditions employed here is suitable for chemoselective oxidation of secondary
It is provided herein a benzobicycloalkane derivative, and a preparation method and use thereof. In particular, it is provided herein a compound of Formula (I), or a pharmaceutically acceptable salt, stereoisomer or solvate thereof, a preparation method, and a use thereof in preparation of drugs for treating pain.
Synergetic Organocatalysis for Eliminating Epimerization in Ring-Opening Polymerizations Enables Synthesis of Stereoregular Isotactic Polyester
作者:Maosheng Li、Yue Tao、Jiadong Tang、Yanchao Wang、Xiaoyong Zhang、Youhua Tao、Xianhong Wang
DOI:10.1021/jacs.8b09739
日期:2019.1.9
ring-opening polymerization of OCAs without epimerization. The close vicinity of both activating groups in the same molecule engenders an amplified synergetic effect and thus allows for the use of mild bases, thereby leading to minimal epimerization for polymerization. Ring-opening polymerization of manOCA monomer (OCA from mandelic acid) mediated by the bifunctional single-molecule organocatalyst yields
O-羧酸酐 (OCA) 的开环聚合可为聚酯提供多种官能团,而传统上这些官能团很难通过内酯聚合获得。典型的开环催化剂不可避免地会发生大多数 OCA 单体的外消旋化,这阻碍了高度等规结晶聚合物的合成。在这里,我们描述了一种有效的双功能单分子有机催化,用于无差向异构化的 OCA 选择性开环聚合。同一分子中两个活化基团的紧密相邻会产生放大的协同效应,从而允许使用温和的碱,从而使聚合的差向异构化最小化。由双功能单分子有机催化剂介导的 manOCA 单体(来自扁桃酸的 OCA)的开环聚合产生高度全同立构的聚(扁桃酸)(PMA),其分子量受控(高达 19.8 kg mol-1)。PMA 的两种对映异构体的混合在该区域产生了结晶立体复合物的第一个例子,它在 150 °C 左右显示出不同的 Tm 值。值得注意的是,双功能催化剂具有防潮、可回收和易于使用的特点,允许可持续和可扩展地合成有规立构功能聚酯。