在此,我们报道了由镍分子催化剂介导的碳酸炔丙酯催化还原为丙二烯。该催化系统使用光作为驱动力,胺作为唯一的氢源。与其他催化方法相反,该过程的进行无需金属氢化物物质的中介。过渡金属催化还原过程中常见的途径被涉及一系列电子转移和质子转移的途径所取代。使用这种催化方法,可以在温和条件下获得多种丙二烯。实验研究支持三烷基胺作为还原剂和质子源的双重作用,并揭示了该反应的关键机理特征。提出了Ni( II ) 联烯基中间体的关键原脱镍步骤来解释还原过程。最后,我们还证明选择性 S N 2 ' 还原过程也可以通过电化学方法有效驱动。
N-Heterocyclic Carbene-Catalyzed Internal Redox Reaction of Alkynals: An Efficient Synthesis of Allenoates
摘要:
An efficient N-heterocyclic carbene (NHC)-catalyzed internal redox reaction of alkynals that bear a y leaving group has been developed. This process provides a new access to a range of allenoates in good yields. Preliminary results demonstrate that the enantioselective variant can also be achieved.
Synthesis of Functionalized [3], [4], [5] and [6]Dendralenes through Palladium‐Catalyzed Cross‐Couplings of Substituted Allenoates
作者:Daniel J. Lippincott、Roscoe T. H. Linstadt、Michael R. Maser、Bruce H. Lipshutz
DOI:10.1002/anie.201609636
日期:2017.1.16
A mild method for the synthesis of highly functionalized [3]–[6]dendralenes is reported, representing a general strategy to diversely substituted higher homologues of the dendralenes. The methodology utilizes allenoates bearing various substitution patterns, along with a wide range of boron and alkenyl nucleophiles that couple under palladium catalysis leading to sp‐, sp2‐, and sp3‐substituted arrays
α-Fluoroallenoate Synthesis via N-Heterocyclic Carbene-Catalyzed Fluorination Reaction of Alkynals
作者:Xu Wang、Zijun Wu、Jian Wang
DOI:10.1021/acs.orglett.5b03615
日期:2016.2.5
The first catalytic alpha-fluoroallenoate synthesis is described. With a suitable combination of N-heterocyclic carbene precatalyst, base, and fluorine reagent, the reaction proceeded smoothly to yield a wide range of alpha-fluoroallenoates with excellent chemoselectivity. These substituted alpha-fluorinated allenoates have been synthesized for the first time, and they are versatile synthetic intermediates toward other useful fluorine-containing building blocks.