We report the preparation of solid and air‐stable polyfunctionalized alkynylzinc pivalates from the corresponding alkynes using TMPZnOPiv (TMP=2,2,6,6‐tetramethylpiperidyl) as base. These organozinc pivalates are obtained as powders under mild conditions in excellent yields and can be manipulated in air for several hours without significant decomposition. These zinc reagents show an excellent reactivity
A new catalytic method for the denitrogenative transannulation/cyclopropanation of in‐situ‐generated 2‐(diazomethyl)pyridines is described using a cobalt‐catalyzed radical‐activation mechanism. The method takes advantage of the inherent properties of a CoIII‐carbene radical intermediate and is the first report of denitrogenative transannulation/cyclopropanation by a radical‐activation mechanism, which
Z-Selective Addition of Diaryl Phosphine Oxides to Alkynes via Photoredox Catalysis
作者:Huamin Wang、Yongli Li、Zilu Tang、Shengchun Wang、Heng Zhang、Hengjiang Cong、Aiwen Lei
DOI:10.1021/acscatal.8b02617
日期:2018.11.2
Radical addition to alkynes is known to predominantly yield thermodynamically more stable E-alkenes. Control of stereoselectivity in these reactions, and the isolation of the higher-energy Z-alkenes, remain an important challenge in chemical synthesis. Herein, directsynthesis of Z-alkenylphosphine oxides via visible-light-induced radical addition to alkynes in water is reported. This protocol was
已知向炔烃中自由基加成主要产生热力学上更稳定的E-烯烃。这些反应中立体选择性的控制以及高能Z-烯烃的分离仍然是化学合成中的重要挑战。本文中,报道了通过可见光诱导的自由基加成至水中的炔烃直接合成Z-烯基膦氧化物。该方案对各种末端和内部炔烃均有效,可提供具有高Z-立体选择性的产物。此外,这种转化以克为单位进行了证明。机理研究支持以下结论:(1)通过自由基加成反应。(2)K 2 CO 3的选择因为水性碱对转化至关重要;(3)π–π堆积相互作用极大地提高了Z选择性。
Copper-Catalyzed Ring Opening of [1.1.1]Propellane with Alkynes: Synthesis of Exocyclic Allenic Cyclobutanes
作者:Dániel Lasányi、Gergely L. Tolnai
DOI:10.1021/acs.orglett.9b03999
日期:2019.12.20
Despite the long history and interesting properties of propellanes, these compounds still have tremendous potential to be exploited in synthetic organic chemistry. Herein we disclose an experimentally simple procedure to achieve cyclobutane-containing allenes and alkynes through a copper-catalyzed ring opening of [1.1.1]propellane and subsequent reaction with ethynes.
The addition of terminal alkynes to acrylate esters in the presence of a ruthenium catalyst and chloride sources proceeds to give the corresponding γ,δ-alkynyl esters in good yields.