Combined Experimental and Computational Investigations of Rhodium- and Ruthenium-Catalyzed C–H Functionalization of Pyrazoles with Alkynes
作者:Andrés G. Algarra、Warren B. Cross、David L. Davies、Qudsia Khamker、Stuart A. Macgregor、Claire L. McMullin、Kuldip Singh
DOI:10.1021/jo402592z
日期:2014.3.7
which then undergoes C–H bond cleavage via proton transfer to acetate. For the reaction of 3-phenyl-5-methylpyrazole with 4-octyne kH/kD = 2.7 ± 0.5 indicating that C–H bond cleavage is rate limiting in this case. However, H/D exchangestudies, both with and without added alkyne, suggest that the migratory insertion transition state is close in energy to that for C–H bond cleavage. In order to model
关于炔烃与3-芳基吡唑在[Rh(MeCN)3 Cp *] [PF 6 ] 2和[RuCl 2(p- cymene)] 2催化剂上偶联机理的详细实验和计算研究已报道。密度泛函理论(DFT)的计算表明一种机制涉及连续的N–H和C–H键激活,HOAc /炔烃交换,迁移插入和C–N还原偶联。对于铑,C-H键活化是包括κ一个两步过程2 -κ 1个位移乙酸,得到agostic中间体,其然后通过质子转移到乙酸经历C-H键断裂。用于3-苯基-5-甲基吡唑与4-辛炔的反应k H / k D = 2.7±0.5,表明在这种情况下C–H键的裂解是限速的。但是,无论是否添加炔烃,H / D交换研究都表明,迁移插入过渡态的能量与C–H键断裂的能量接近。为了正确地对此结果建模,DFT计算必须采用完整的实验系统,并包括色散效应的处理。在Ru(p -cymene)}处计算出明显更高的整体催化势垒,其限速过程仍为CH活化。然而,这是现在对应于κ一个一步法2
Electrochemical rhodium catalysed alkyne annulation with pyrazoles through anodic oxidation – a metal oxidant/additive free methodology
作者:Subban Kathiravan、Prasad Anaspure
DOI:10.1039/d2ob02306g
日期:——
A rhodium(iii) catalysed electrochemical C–H annulation of alkynes with pyrazole without using metal oxidants/additives is reported.