KOAc-promoted alkynylation of α-C–H bonds of ethers with alkynyl bromides under transition-metal-free conditions
作者:Jiajun Zhang、Pinhua Li、Lei Wang
DOI:10.1039/c4ob00002a
日期:——
KOAc-promoted α-position C–H activation and alkynylation of ethers with alkynyl bromides to 2-alkynyl ethers was developed under transition-metal-free conditions.
Visible Light‐Enabled sp
<sup>3</sup>
‐C−H Functionalization with Chloro‐ and Bromoalkynes: Chemoselective Route to Vinylchlorides or Alkynes
作者:Tapas Adak、Marvin Hoffmann、Sina Witzel、Matthias Rudolph、Andreas Dreuw、A. Stephen K. Hashmi
DOI:10.1002/chem.202001259
日期:2020.12
valuable vinyl chlorides. The photo‐organocatalytic hydrogen atom transfer strategy gives rise to a broad range of diversely functionalized olefins. When bromoalkynes are applied in the presence of a base, a chemoselectivity switch to an alkynylation is observed. This reaction can even be performed for the alkynylation of unactivated sp3‐C−H bonds, in this case with a preference of the more substituted
实现了氯炔的前所未有的直接原子经济化学和区域选择性加氢烷基化和溴炔的 sp 3 -C-H 炔基化。反应伙伴是未官能化的醚、醇、酰胺,甚至未活化的烃。我们发现家用荧光灯能够激发二芳基酮,然后二芳基酮选择性地从 sp 3 ‐C−H 键中提取 H 原子。用氯炔获得正式炔插入 sp 3 ‐C−H 键的产物,从而提供有价值的氯乙烯。光有机催化氢原子转移策略产生了多种不同官能化的烯烃。当在碱存在下应用溴代炔时,观察到化学选择性转变为炔基化。该反应甚至可以用于未活化的 sp 3 -C-H 键的炔基化,在这种情况下优选取代更多的碳。伴随的量子化学计算表明乙烯基自由基中间体与碳自由基中心具有明显的线性配位,从而能够在H原子抽象后形成两种非对映异构体,表明( Z )-非对映异构体是优选的,这支持了实验观察到的( E / Z )‐分布。
Photochemical Functionalization of Heterocycles with EBX Reagents: C−H Alkynylation versus Deconstructive Ring Cleavage**
作者:Errika Voutyritsa、Marion Garreau、Maroula G. Kokotou、Ierasia Triandafillidi、Jérôme Waser、Christoforos G. Kokotos
DOI:10.1002/chem.202002868
日期:2020.11.11
The development of novel methodologies for the functionalization of saturated heterocycles is highly desirable. Herein, we report a cheap and efficient photochemical method for the C−H functionalization of saturated O‐heterocycles, as well as the deconstructive ring‐cleavage of S‐heterocycles, employing hypervalent iodine alkynylation reagents (ethynylbenziodoxolones, EBX). This photochemical alkynylation
Visible‐Light‐Induced Alkynylation of α‐C–H Bonds of Ethers with Alkynyl Bromides without External Photocatalyst
作者:Xiaofei Xie、Jie Liu、Lei Wang、Min Wang
DOI:10.1002/ejoc.201900872
日期:2020.3.15
An unprecedented direct alkynylation reaction of α‐C(sp3)–H bonds of ethers under visiblelight irradiation at room temperature withoutexternalphotocatalyst was developed.
Functionalisation of ethereal-based saturated heterocycles with concomitant aerobic C–H activation and C–C bond formation
作者:Nehaal Ahmed、Richard J. Spears、Tom D. Sheppard、Vijay Chudasama
DOI:10.1039/d2sc01626e
日期:——
emphasis on sustainable synthesis, aerobic C–Hactivation (the use of oxygen in air to activateC–H bonds) represents a highly attractive conduit for the development of novel synthetic methodologies. Herein, we report the air mediated functionalisation of various saturated heterocycles and ethers via aerobically generated radical intermediates to form new C–C bonds using acetylenic and vinyl triflones as radical