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。
Ceric Ammonium Nitrate (CAN) Promoted Pd<sup>II</sup>-Catalyzed Substrate-Directed<i>o</i>-Benzoxylation and Decarboxylative<i>o</i>-Aroylation
作者:Sourav Kumar Santra、Arghya Banerjee、Nilufa Khatun、Bhisma K. Patel
DOI:10.1002/ejoc.201403367
日期:2015.1
Inexpensive cericammoniumnitrate (CAN) is an efficient oxidant for the Pd-catalyzed substrate-directed o-benzoxylation and decarboxylative o-aroylation processes. In the presence of CAN, the reaction of directing arenes with carboxylic acids resulted in o-benzoxylated products, whereas a decarboxylative o-aroylation occurred by using α-keto acids, which led to the formation of o-aroylation products
廉价的硝酸铈铵 (CAN) 是 Pd 催化的底物导向邻苯甲氧基化和脱羧邻芳酰化过程的有效氧化剂。在 CAN 存在下,定向芳烃与羧酸反应生成邻苯甲酰化产物,而使用 α-酮酸发生脱羧邻芳酰化,从而形成邻芳酰化产物。
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.
Nickel-catalyzed regioselective C–H acylation of chelating arenes: a new catalytic system for C–C bond formation <i>via</i> a radical process and its mechanistic explorations
作者:Ze-lin Li、Peng-yu Wu、Kang-kang Sun、Chun Cai
DOI:10.1039/c9nj02191d
日期:——
ortho C–Hbond of chelating arenes via the Ni(II)-catalyzed cross dehydrogenative coupling strategy has been developed here. This new procedure exhibits excellent regioselectivity and good functional group tolerance. This discovery could be of great importance for the C–H acylation reactions of chelating arenes without any extraneous directing group and for the application of nickel-catalyzed C–H activation
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.