通过NHPI的双氧激活,在Pd(II)催化的C(sp 2)-H活化过程中,生物相关的杂环支架与芳基甲烷的芳基化反应进行了脱氢偶联。质谱和基于1 H NMR的动力学同位素效应研究表明,CH键的活化是决定速率的步骤。自由基清除实验表明存在自由基途径。在1等分试样的反应混合物的1 H NMR和用2-氨基硫代苯酚原位捕集揭示芳基甲烷的需氧氧化过程中醛的形成。该反应对于芳酰基源和包括苯并噻唑,苯并恶唑,吡啶,喹喔啉,嘧啶和偶氮芳烃的导向基团的不同变化具有广泛的范围。发现苄基亚甲基部分是芳酰基碳的来源,最优选苄基醚部分,其次是芳基醛和芳基甲烷的羰基。但是,芳基甲烷的易得性使其成为芳酰基源最具吸引力。可以实现时间依赖性的选择性单-和双-芳基化。1 3-二芳基嘧啶表现出2-苯基部分的区域选择性芳酰基化,而与3-苯基部分中是否存在任何取代基(吸电子或供电子)无关。对于不对称的偶氮芳烃,在带有取代基的苯基部分中发生选择性芳酰基化。
Palladium-catalyzed oxidative ortho-acylation of 2-arylbenzoxazoles and 2-arylbenzothiazoles with toluene derivatives
作者:Yong Zheng、Wei-Bin Song、Shu-Wei Zhang、Li-Jiang Xuan
DOI:10.1016/j.tet.2015.01.025
日期:2015.3
A palladium-catalyzed oxidative ortho-acylation of 2-arylbenzoxazoles and 2-arylbenzothiazoles using TBHP as oxidant was developed, in which readily available toluene derivatives were used as the in situ generated acyl sources. This reaction afforded the desired products in moderate to good yields, and exhibited excellent regioselectivity. The plausible mechanism was also proposed.
Peroxide-Free Pd(II)-Catalyzed Ortho Aroylation and Ortho Halogenation of Directing Arenes
作者:Sourav Kumar Santra、Arghya Banerjee、Prakash Ranjan Mohanta、Bhisma K. Patel
DOI:10.1021/acs.joc.6b01170
日期:2016.7.15
A Pd(II)-catalyzed peroxide-free ortho aroylation of directing arenes has been developed via cross dehydrogenative coupling (CDC) in the presence of the terminal oxidant Cu(OAc)2·H2O. Ortho aroylation of directing arenes proceeds via decarbonylation of the in situ generated phenyl glyoxal, which is obtained from 2-acetoxyacetophenone in the presence of the oxidant Cu(OAc)2·H2O. However, changing the
Pd(<scp>ii</scp>)-catalysed o-aroylation of directing arenes using terminal aryl alkenes and alkynes
作者:Nilufa Khatun、Arghya Banerjee、Sourav K. Santra、Ahalya Behera、Bhisma K. Patel
DOI:10.1039/c4ra11014e
日期:——
A substrate-directed Pd-catalysed o-aroylation strategy has been demonstrated using new aroyl surrogates viz. terminal aryl alkenes and alkynes in the presence of TBHP. By a subtle change in catalyst from Cu to Pd, a differential selectivity is observed. While terminal aryl alkenes/alkynes in the presence of Cu/TBHP are reported to act as o-aryloxy (ArCOO–) sources, the use of Pd/TBHP installs an aroyl (ArCO–) group at the ortho position with respect to the directing arenes.
Palladium-Catalyzed<i>ortho</i>-Aroylation of 2-Arylbenzothiazoles and 2-Arylbenzoxazoles with Aldehydes
作者:Arghya Banerjee、Sourav Kumar Santra、Srimanta Guin、Saroj Kumar Rout、Bhisma K. Patel
DOI:10.1002/ejoc.201201503
日期:2013.3
protocol for the ortho-aroylation of 2-arylbenzothiazoles and 2-arylbenzoxazoles has been developed using aldehydes as the aroyl source. This Pd-catalyzed substrate-directed sp2-hybridized C–H bond functionalization occurs in the presence of the oxidant tert-butyl hydroperoxide. A variety of functional groups on the 2-arylbenzothiazoles, 2-arylbenzoxazoles, and aldehydes are tolerated under the reaction