通过初始速率法获得了钯(II)催化的苯基硼酸与乙基噻吩-3-乙酸乙酯之间的氧化交叉偶联中关键组分的反应顺序。结果表明,反应速率不仅取决于三氟乙酸钯(反应顺序:0.97)和苯基硼酸(反应顺序:1.26)的浓度,还取决于噻吩(反应顺序:0.55)和氧化银(浓度)的浓度。反应顺序:-1.27)。NMR光谱滴定研究确定了银盐与苯基硼酸和噻吩-3-基乙基乙酸乙酯之间存在1:1的络合物。低反向动力学同位素效应(k H / k D= 0.93)是通过使用乙基噻吩-3-乙酸乙基酯的4氘代异构体并监测其与4-苯基取代产物的反应而确定的。用对位取代的2-苯基噻吩进行的Hammett分析得出与苯基硼酸的氧化交叉偶联的负ρ值。根据动力学数据和其他证据,提出了一种机制,该机制可以将苯基从苯基硼酸转移到三氟乙酸钯和噻吩的1:1络合物中,作为速率确定步骤。提出并讨论了有关中间体的结构。
An efficient phosphine-free direct C–Harylation of thiophenes at the α-position has been developed at low catalyst loading of bis(alkoxo)palladium complex (Cat.I, 0.1–0.2 mol %). The developed synthetic method can be applied to the synthesis of α-aryl/heteroaryl thiophenes from aryl or heteroaryl bromides in good to excellent yields and is compatible with the substrates bearing electron-donating or
Transition-Metal-Free Sulfuration/Annulation of Alkenes: Economical Access to Thiophenes Enabled by the Cleavage of Multiple C–H Bonds
作者:Liang Chen、Hao Min、Weilan Zeng、Xiaoming Zhu、Yun Liang、Guobo Deng、Yuan Yang
DOI:10.1021/acs.orglett.8b03078
日期:2018.12.7
and transition-metal-free strategy for the synthesis of thiophenes from substituted buta-1-enes with potassium sulfide has been presented. The reaction achieves double C–Sbondformations via cleavage of multiple C–H bonds and provides an efficientapproach to access various functionalized thiophenes. Moreover, the strategy can also be used for the synthesis of thiophenes from 1,4-diaryl-1,3-dienes.
Metal-Free C–S Bond Formation in Elemental Sulfur and Cyclobutanol Derivatives: The Synthesis of Substituted Thiophenes
作者:Mingzhong Wu、Chaoxian Yan、Daijiao Zhuang、Rulong Yan
DOI:10.1021/acs.orglett.2c01907
日期:2022.7.29
A general approach for the metal-free synthesis of thiophenes by tert-cyclobutanols and elementalsulfur has been developed. This protocol provides a strategy for constructing multisubstituted thiophene derivatives via C–S bond formation under air. This reaction shows good functionality tolerance under the reaction conditions, and the mechanism is validated by control experiments and density functional