An economical and environmentally friendly oxidative biaryl coupling promoted by activated MnO<sub>2</sub>
作者:Jingjing Yang、Shutao Sun、Ziyu Zeng、Hongbo Zheng、Wei Li、Hongxiang Lou、Lei Liu
DOI:10.1039/c4ob01409j
日期:——
An activated manganese dioxide (MnO2)–BF3·OEt2 oxidation system was developed to efficiently mediate the intramolecular as well as intermolecular biaryl coupling. The oxidative coupling proceeds smoothly at ambient temperature to deliver the corresponding five- to eight-membered tricyclic products in good to excellent yields. The employment of the combination of MnO2 and BF3·OEt2 is attractive on the basis of economical and environmental issues.
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
Modular Access to 9,9-Spirobifluorenes by Oxidative Coupling Using Molybdenum Pentachloride
The strong oxidizing agent molybdenum pentachloride was used for an efficient direct C-C bond formation of 9,9-diarylfluorenes to the corresponding 9,9-spirobifluorenes. Thus, a versatile method that is compatible with labile groups, such as iodo moieties, was established. By this approach important building blocks for light emitting polymers were synthesized in high yields.
Oxidative C−C Bond Formation (Scholl Reaction) with DDQ as an Efficient and Easily Recyclable Oxidant
作者:Linyi Zhai、Ruchi Shukla、Rajendra Rathore
DOI:10.1021/ol901331p
日期:2009.8.6
DDQ in the presence of an acid is known to oxidize a variety of aromatic donors to the corresponding cation radicals. Herein, we now demonstrate that the DDQ/H+ system can be effectively utilized for the oxidative C-C bond formations or biaryl synthesis. The efficient preparation of a variety of polyaromatic hydrocarbons including graphitic hexa-peri-hexabenzocoronenes, ease of isolation of the clean products, and ready regeneration of DDQ from easily recovered reduced DDQ-H-2 advances the use of DDQ/H+ for Scholl reactions.
ARCOLEO A.; NATOLI M. C.; MARINO M. L., SYNTH. COMMUN., 1975, 5, NO 4, 287-292