Low-valent titanium and zirconium reagents in situ prepared from metallocene dichlorides (Cp2MCl2: M = Ti, Zr) and magnesium powder activated by 1,2-dibromoethane smoothly reacted with allylpropargylethers to afford 3-methylenetetrahydrofurans in good yields. It is noteworthy that the Cp2Zr- and Cp2Ti-mediated cyclizations proceed with inverse stereoselectivity.
A Simple Nickel Catalyst Enabling an
<i>E</i>
‐Selective Alkyne Semihydrogenation
作者:Niklas O. Thiel、Benyapa Kaewmee、Trung Tran Ngoc、Johannes F. Teichert
DOI:10.1002/chem.201903850
日期:2020.2.3
Stereoselective alkyne semihydrogenations are attractive approaches to alkenes, which are key building blocks for synthesis. With regards to the most atom‐economic reducing agent dihydrogen (H2), only few catalysts for the challenging E‐selectivealkyne semihydrogenation have been disclosed, each with a unique substrate scope profile. Here, we show that a commercially available nickel catalyst facilitates
立体选择性炔烃半氢化是制备烯烃的有吸引力的方法,烯烃是合成的关键组成部分。对于最具原子经济性的还原剂二氢(H 2 ),仅公开了少数用于具有挑战性的E-选择性炔烃半氢化的催化剂,每种催化剂都具有独特的底物范围特征。在这里,我们表明,市售的镍催化剂促进了多种取代内炔的E-选择性炔烃半氢化。这产生了一个简单且广泛适用的整体方案,用于使用 H 2立体选择性地访问E-烯烃,这可以作为通用的合成方法。
Tributylmanganate(II)-Mediated Cyclization of Enynes
Treatment of enynes with tributylmanganate(II) provided cyclized products containing alkylidene substituents. 1-Tridecen-6-yne or 1-tetradecen-7-yne gave 1-heptylidene-2-methylcyclopentane or 1-heptylidene-2-methylcyclohexane in 67 or 50% yield, respectively upon treatment with tributylmanganate(II). The reaction of dimethylvinylsilyl ether of 3-decyn-1-ol with tributylmanganate(II) afforded 4-heptylidene-2,2,3-trimethyl-1-oxa-2-silacyclohexane in good yield.
Defunctionalization of sp<sup>3</sup> C–Heteroatom and sp<sup>3</sup> C–C Bonds Enabled by Photoexcited Triplet Ketone Catalysts
作者:Yiting Gu、Hongfei Yin、Matthew Wakeling、Juzeng An、Ruben Martin
DOI:10.1021/acscatal.1c05329
日期:2022.1.21
defunctionalization of sp3 C–heteroatom and sp3 C–C bonds with tripletketone catalysts and bipyridine additives is disclosed. This protocol is characterized by its broad scope without recourse to transition metal catalysts or stoichiometric exogeneous reductants, thus offering a complementary technique for activating σ sp3 C–C(heteroatom) bonds. Preliminary mechanistic studies suggest that the presence
Consecutive visible-light photoredox decarboxylative couplings of adipic acid active esters with alkynyl sulfones leading to cyclic compounds
作者:Jingjing Li、Hua Tian、Min Jiang、Haijun Yang、Yufen Zhao、Hua Fu
DOI:10.1039/c6cc04386k
日期:——
active esters (bis(1,3-dioxoisoindolin-2-yl)-substituted hexanedioates) with substituted 1-(2-arylethynylsulfonyl)benzenes have been developed under visible-light photocatalysis. The successive photoredox decarboxylative C-Cbondformation...