Catalyst Control in Positional-Selective C–H Alkenylation of Isoxazoles and a Ruthenium-Mediated Assembly of Trisubstituted Pyrroles
作者:Pravin Kumar、Manmohan Kapur
DOI:10.1021/acs.orglett.9b00446
日期:2019.4.5
determining the positional selectivity in C–H alkenylation of isoxazoles. A cationic rhodium-mediated, strong-directing group promotes C(sp2)-H activation at the proximal aryl ring whereas, the palladium-mediated electrophilic metallation leads to the C(sp2)-H activation at the distal position of the directing group. Synthetic elaboration of this C–H alkenylation product via ruthenium and copper co-catalysis
Unusual Reactivity of 4-Vinyl Isoxazoles in the Copper-Mediated Synthesis of Pyridines, Employing DMSO as a One-Carbon Surrogate
作者:Pravin Kumar、Manmohan Kapur
DOI:10.1021/acs.orglett.0c01935
日期:2020.8.7
An efficient protocol for the synthesis of nicotinate derivatives and tetrasubstituted pyridines through a copper-mediated cleavage of isoxazoles has been developed. The highlight of the work is the observation of an unusualreactivity of 4-vinyl isoxazoles under the reaction conditions. DMSO serves as a one-carbon surrogate generating an active methylene group during the reaction to form two C–C bonds
One-pot regioselective synthesis of substituted pyrazoles and isoxazoles in PEG-400/water medium by Cu-free nano-Pd catalyzed sequential acyl Sonogashira coupling–intramolecular cyclization
Catalyst efficacy of in situ generated Pd-nanoparticles (PdNPs) in the regioselective one-pot synthesis of 3,5-di & 3,4,5-trisubstituted pyrazoles and 3,5-disubstituted isoxazoles in environmentally benign PEG-400/H2O medium, which involves the sequential (i) Cu-free acyl-Sonogashira coupling (ASC) and (ii) intramolecular ynone–amine cyclization under PTC conditions was described. The results of controlled
在环境友好的PEG-400 / H 2中原位生成的Pd-纳米颗粒(PdNPs)在区域选择性一锅合成3,5-di和3,4,5-三取代的吡唑和3,5-二取代的异恶唑的催化剂效力描述了一种O介质,它涉及(i)在PTC条件下无Cu的酰基-Sonogashira偶联(ASC)和(ii)分子内的ynone-amine环化。受控实验的结果支持两个连续的催化循环(ASC /环化)的操作,并通过一锅法通过与炔酮结合的钯实现互补/相反的区域选择性。而且,就地一锅法反应序列的第一个催化循环后回收的PdNPs已连续五次再次使用。此外,在进行上述研究之前,某些常见的Pd-N-杂环卡宾(Pd-NHC)配合物在水和有机物中催化相同的一锅两步反应顺序(无铜ASC /环化)的功效还优化了溶剂。还可以从水中的Pd-NHC上方原位生成PdNP,但由于它们的尺寸较大,因此无法重复使用。
Ru(<scp>ii</scp>)-Catalyzed, Cu(<scp>ii</scp>)-mediated carbene migratory insertion in the synthesis of trisubstituted pyrroles from isoxazoles
A convenient, “one-pot” synthesis of trisubstituted pyrroles via a Ru(II)-catalyzed, Cu(II)-mediated reaction of substituted isoxazoles with sulfonylhydrazones has been developed. A series of highly functionalized pyrroles are obtained via a synergistic formation of new C−C and C−N bonds. Mechanistic investigations were carried out to propose the plausible pathway. This protocol provides a facile and
通过Ru( II ) 催化的、Cu( II ) 介导的取代异恶唑与磺酰腙的反应,一种方便的“一锅法”合成三取代吡咯得到了开发。通过新的 C-C 和 C-N 键的协同形成,获得了一系列高度功能化的吡咯。进行了机制研究以提出合理的途径。该协议为合成各种带有吡咯骨架的杂环化合物提供了一种简便快捷的方法。