carbonylation reaction for the synthesis of fluoren‐9‐ones from 2‐halogenated biphenyls using phenyl formate as a carbon monoxide surrogate was achieved. The combined use of cesium carbonate and o‐anisic acid resulted in a remarkable rate enhancement, where the reaction was complete within 3 min in some cases. Mechanistic studies indicated that the turnover‐limiting step of the reaction was the C−H bond‐cleaving
Rhodium-Catalyzed Intramolecular C−H Silylation by Silacyclobutanes
作者:Qing-Wei Zhang、Kun An、Li-Chuan Liu、Shuangxi Guo、Chenran Jiang、Huifang Guo、Wei He
DOI:10.1002/anie.201602376
日期:2016.5.17
Silacyclobutane was discovered to be an efficient C−H bond silylation reagent. Under the catalysis of RhI/TMS‐segphos, silacyclobutane undergoes sequential C−Si/C−H bond activations, affording a series of π‐conjugated siloles in high yields and regioselectivities. The catalytic cycle was proposed to involve a rarely documented endocyclic β‐hydride elimination of five‐membered metallacycles, which after
发现硅环丁烷是一种有效的CH键甲硅烷基化试剂。在Rh I / TMS-segphos的催化下,硅环丁烷经历了连续的C-Si / C-H键活化,从而以高收率和区域选择性提供了一系列π-共轭硅化物。有人提出催化循环涉及很少有文献记载的五元金属环的环内β-氢化物消除,在还原性消除后会产生能够进行CH活化的Si-Rh I物种。
Palladium-Catalyzed Cyclocoupling of 2-Halobiaryls with Isocyanides via the Cleavage of Carbon−Hydrogen Bonds
2-halobiaryls with isocyanides was developed. The reaction afforded an array of fluorenone imine derivatives via the cleavage of a C−H bond at the 2′-position of 2-halobiaryls. The use of 2,6-disubstitutedphenyl isocyanide was crucial for this catalytic cyclocoupling reaction to proceed. The reaction was applicable to heterocyclic and vinylic substrates, allowing the construction of a wide range of
为了证明异氰化物在催化CH键官能化反应中的实用性,开发了2-卤代双芳基与异氰化物的钯催化的环偶联反应。该反应通过在2-卤代联芳基的2'-位上的CH键断裂,提供了一系列芴酮亚胺衍生物。2,6-二取代的苯基异氰化物的使用对于进行该催化环偶联反应至关重要。该反应适用于杂环和乙烯基底物,从而允许构建广泛的环系统。观察到的大的动力学同位素效应(k H / k D = 5.3)表明,CH键的活化是该催化作用中的周转限制步骤。
Palladium-Catalyzed Synthesis of Dibenzophosphole Oxides via Intramolecular Dehydrogenative Cyclization
Dibenzophosphole oxides were obtained from secondary hydrophosphine oxides with a biphenyl group by dehydrogenation via phosphine–hydrogen and carbon–hydrogen bond cleavage in the presence of a catalytic amount of palladium(II) acetate, Pd(OAc)2. By using this reaction, a ladder-type dibenzophosphole oxide could also be synthesized by double intramolecular dehydrogenative cyclization.