Palladium-Catalyzed Aryl C(sp2)–H Bond Hydroxylation of 2-Arylpyridine Using TBHP as Oxidant
摘要:
An efficient synthesis of phenols via Pd-catalyzed, pyridyl-directed homogeneous hydroxylation of the aryl C-H bond was developed, in which tert-butyl hydroperoxide was used as the sole oxidant. The method had a broad group tolerance and was available for both electron-rich and electron-deficient substrates. The reaction of a series of 2-arylpyridine derivatives gave the ortho-hydroxylation products in moderate to good yields.
We have developed an efficient Pd‐catalyzed directed C—H bromination protocol, in which dimethyl sulfoxide (DMSO) is employed as oxidant with hydrobromic acid aqueous solution (HBr(aq)) as bromide source. The DMSO/HBr(aq) system, which is novelly and efficiently utilized in transition‐metal catalyzed C—H activation, illustrates its practicability by the operational simplicity, inexpensive and readily
Brønsted Acid Enhanced Rhodium-Catalyzed Conjugate Addition of Aryl CH Bonds to α,β-Unsaturated Ketones under Mild Conditions
作者:Lei Yang、Bo Qian、Hanmin Huang
DOI:10.1002/chem.201201348
日期:2012.7.27
With a Brønsted acid as the solvent, the rhodium‐catalyzed direct addition of arylCH bonds to α,β‐unsaturated ketones was realized undermild reaction conditions (see scheme). The acid may assist by interceding in the conflict of the two proton‐transfer events and averting the substrate inhibition involved in this type of CH addition reaction.
A novel and efficient Rh/O2 catalytic system has been developed and shown to catalyze highly efficient oxidative C-H activation/annulation reactions, producing a broad range of isoquinolinium salts with high turnover numbers (up to 740). Mechanistic studies provided strong evidence of facile oxidation of Rh(I) to Rh(III) by molecularoxygen facilitated by acid.
Cu-Mediated Direct Aryl CH Halogenation: a Strategy to Control Mono- and Di-Selectivity
作者:Zhi-Jun Du、Lian-Xun Gao、Ying-Jie Lin、Fu-She Han
DOI:10.1002/cctc.201300734
日期:2014.1
A protocol for the copper‐mediated directarylCHhalogenation is presented. Highly selective mono‐ and di‐halogenations are achieved by using acyl hypohalites, generated in situ from the readily available carboxylic acid and N‐halosuccinimides (NXS; X=Br and Cl) as powerful halogenating reagents. The correct choice of carboxylic acid additives and solvents is essential for both high yield and selectivity
提出了铜介导的直接芳基CH卤化的方案。通过使用酰基次卤酸盐来实现高度选择性的单卤化和二卤化,酰基次卤酸盐是由现成的羧酸和N-卤代琥珀酰亚胺(NXS; X = Br和Cl)原位生成的,作为强力卤化试剂。正确选择羧酸添加剂和溶剂对于高收率和选择性都至关重要。因此,使用廉价的铜催化剂和从容易负担得起且易于处理的羧酸和NXS(X = Br和Cl)原位生成酰基次卤酸盐卤化试剂的新策略为实际应用提供了优势。
C−H Activation Based Copper‐Catalyzed One‐Shot Synthesis of N,O‐Bidentate Organic Difluoroboron Complexes
作者:Guangying Tan、Malte L. Schrader、Constantin Daniliuc、Felix Strieth‐Kalthoff、Frank Glorius
DOI:10.1002/anie.202008311
日期:2020.11.23
Organic BF2 complexes exhibit characteristics such as large Stokes shift, high quantum yield, strong emission intensity, and robust chemical stability, thereby being extensively used in various applications. Herein, we disclose a novel copper‐catalyzed cascade C−H activation/acyloxylation and difluoroboronation of 2‐phenylpyridine derivatives, thus providing a straightforward and rapid gateway to a