mechanism of the reductive functionalization of graphene. The well-defined molecular HBC system enabled deeper insights into the mechanism of the alkylation of reductively activated nanographenes. The separation and complete characterization of alkylationproducts clearly demonstrate that nanographene functionalization proceeds with exceptionally high regio- and stereoselectivities on the HBC scaffold.
Probing the Arenium-Ion (ProtonTransfer) versus the Cation-Radical (Electron Transfer) Mechanism of Scholl Reaction Using DDQ as Oxidant
作者:Linyi Zhai、Ruchi Shukla、Shriya H. Wadumethrige、Rajendra Rathore
DOI:10.1021/jo100611k
日期:2010.7.16
DDQ/H+ system readily oxidizes a variety of electron donors with oxidation potential as high as ∼1.7 V to the corresponding cationradicals. A re-examination of the controversial arenium-ion versus cation-radical mechanisms for Scholl reaction using DDQ/H+ together with commonly utilized FeCl3 as oxidants led us to demonstrate that the reaction proceeds largely via a cation-radical mechanism. The critical
DDQ / H +系统易于将各种电子供体氧化,氧化电位高达1.7 V,可氧化成相应的阳离子自由基。使用DDQ / H +和常用的FeCl 3作为氧化剂对Scholl反应中有争议的氢离子与阳离子自由基机理的重新检验,使我们证明反应主要是通过阳离子自由基机理进行的。支持Scholl反应的阳离子自由基途径的重要实验证据包括:(i)在二氯甲烷和各种酸(10%v / v)的混合物中,Scholl前体中没有反应。(ii)必须使用强氧化剂,例如氯化铁(FeCl 3)或DDQ / H +考虑到二氢中间体的芳构化(通过芳烃离子机理形成)可以很容易地用相当弱的氧化剂(例如碘或空气)来完成,因此Scholl反应与芳烃离子机理不一致。(iii)与SCE相比,氧化电位≤1.7V的各种Scholl前体易于形成DDQ / H +作为氧化剂的C-C氧化键,而与SCE相比,氧化电位大于1.7 V的Scholl前体则不会发生
Group 4 Diarylmetallocenes as Bespoke Aryne Precursors for Titanium-Catalyzed [2 + 2 + 2] Cycloaddition of Arynes and Alkynes
作者:Benjamin R. Reiner、Ian A. Tonks
DOI:10.1021/acs.inorgchem.9b01082
日期:2019.8.19
reports describing titanium (Ti)-catalyzed [2 + 2 + 2] cyclotrimerization of alkynes, the incorporation of arynes into this potent manifold has never been reported. The in situ generation of arynes often requires fluoride, which instead will react with the highly fluorophilic Ti center, suppressing productive catalysis. Herein, we describe the use of group 4 diarylmetallocenes, CpR2MAr2 (CpR = C5H5,
尽管有大量报道描述了钛(Ti)催化炔烃的[2 + 2 + 2]环三聚反应,但从未报道过将芳烃掺入到这种有效的歧管中。芳烃的原位生成通常需要氟化物,而氟化物将与高度氟的Ti中心反应,从而抑制生产催化。在这里,我们描述了使用第4组二芳基金属茂CpR2MAr2(CpR = C5H5,C5Me5; M = Ti,Zr)作为芳烃前体,通过与2当量的炔烃偶合,进行Ti催化的取代萘的合成。催化剂负载量为1%时,可获得所需萘产品的中等至良好收率,这比钯或镍催化的类似反应低约一个数量级。此外,萘在电子产品,光伏产品,和制药业,敦促发现更多的经济综合体。这些结果表明,芳烃从CpR2M(η2-芳烃)配合物转移到另一种金属是将芳烃片段引入有机金属催化过程的可行途径。
Efficient Oxidative Coupling of Arenes<i>via</i>Electrochemical Regeneration of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) under Mild Reaction Conditions
作者:Philipp Röse、Steffen Emge、Christoph Alexander König、Gerhard Hilt
DOI:10.1002/adsc.201601331
日期:2017.4.17
dehydrogenative carbon‐carbon bondformation of aromatic rings in the presence of catalytic amounts of an oxidising agent is herein described. The oxidative coupling is realised under indirect anodic conditions, utilising 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) as an efficient redox mediator under acidic conditions. In comparison, for the stoichiometric oxidative coupling reaction of hexakis
A Practical One-Pot Synthesis of Soluble Hexa-<i>p</i><i>eri-</i>hexabenzocoronene and Isolation of Its Cation-Radical Salt
作者:Rajendra Rathore、Carrie L. Burns
DOI:10.1021/jo034271e
日期:2003.5.1
and the oxidative cyclodehydrogenation to planar HBC is achieved in a one-pot reaction using ferricchloride both as a Lewis acid catalyst and as an oxidant in excellent yields. The ready availability of HBC allows the isolation of its pure cation-radical salt using a variety of chemical oxidants such as antimonypentachloride and triethyloxonium and nitrosonium hexachloroantimonate salts.