Palladium-catalyzed ortho-nitration of 2-arylbenzoxazoles
摘要:
An efficient and general protocol for palladium-catalyzed chelation-assisted ortho-nitration of 2-arylbenzoxazoles has been developed. This nitration exhibits high regioselectivity for the substrates, and the reaction could tolerate many functional groups such as F, Cl, Br, CH3, CH3O, affording ortho-nitration products in moderate to good yields. Moreover, some 2-arylbenzoxazole heterocyclic analogues proceed well under this catalytic system. Further studies have been performed to obtain insight into the mechanism. (C) 2015 Elsevier Ltd. All rights reserved.
Synthesis of 2-substituted pyrimidines and benzoxazoles via a visible-light-driven organocatalytic aerobic oxidation: enhancement of the reaction rate and selectivity by a base
作者:Lin Wang、Zhi-Gang Ma、Xiao-Jing Wei、Qing-Yuan Meng、Deng-Tao Yang、Shao-Fu Du、Zi-Fei Chen、Li-Zhu Wu、Qiang Liu
DOI:10.1039/c4gc00337c
日期:——
An efficient visible-light-driven photocatalytic oxidation of various 2-substituted dihydropyrimidines and phenolic imines has been achieved using an organic photocatalyst eosin Y bis(tetrabutyl ammonium salt) (TBA-eosin Y) and inexpensive oxidant molecular oxygen. With the aid of a base, significantly enhanced photoinduced electron transfer from substrates dihydropyrimidines or phenolic imines to the excited state of TBA-eosin Y has enabled the aerobic oxidation to yield 2-(methylthio)pyrimidines or 2-arylbenzoxazoles selectively.
Cooperative bimetallic catalysis is a fundamental approach in modern synthetic chemistry. We report bimetallic cooperative catalysis for the direct decarbonylative heteroarylation of ubiquitous carboxylic acids via acyl C‐O/C‐H coupling. This novel catalytic system exploits the cooperative action of a copper catalyst and a palladium catalyst in decarbonylation, which enables highly chemoselective synthesis
We report herein a two‐step one‐pot strategy for the synthesis of benzoxazoles from amides by using cesium fluoride/copper as catalysts. This approach involves the in situ generation of acyl fluorides from the corresponding amides, and the acyl fluorides undergo transamidation and cyclization to give benzoxazoles in good yields. In this work, the amide C−N bonds are activated by CsF to form the acyl
Chelating palladium complexes containing pyridine/pyrimidine hydroxyalkyl di-functionalized N-heterocyclic carbenes: synthesis, structure, and catalytic activity towards C–H activation
作者:Liangru Yang、Jinwei Yuan、Pu Mao、Qi Guo
DOI:10.1039/c5ra21183b
日期:——
novel chelating palladium complexes containing pyridine/pyrimidine hydroxyalkyl di-functionalized N-heterocyclic carbenes (NHCs) via direct metallation of the precursor imidazolium salts is presented. The structure has been characterized unambiguously by X-ray single crystal analysis. Catalytic activity investigation showed that the complexes catalyse the direct C–H bond arylation of (benzo)oxazoles efficiently
A radical C–H arylation reaction of oxazoles with (hetero)aryl iodides using Cs2CO3 as base/electron donor and 1,1′-bis(diphenylphosphino) ferrocene (dppf) as a catalytic SET mediator is reported. The overall reaction likely follows the general base-promoted homolytic aromaticsubstitution mechanism through a radical-chain pathway. DFT calculations suggest that dppf forms a complex with CsCO3–, enhancing
报道了使用Cs 2 CO 3作为碱/电子给体和1,1'-双(二苯基膦基)二茂铁(dppf)作为催化SET介体,恶唑与(杂)芳基碘化物的自由基CH芳基化反应。整个反应可能通过自由基链途径遵循一般的碱促进的均质芳族取代机理。DFT计算表明,dppf与CsCO 3 –形成络合物,增强了SET还原能力,可从ArI生成芳基。