三取代烯烃的立体选择性合成是有机化学中长期存在的挑战,因为三取代烯烃的 E 和 Z 异构体之间的能量差异很小(与 1,2-二取代烯烃相比)。1,1-二取代烯烃的过渡金属催化异构化可以作为三取代烯烃的替代方法,但由于与反应效率和立体选择性有关的问题,它仍然不发达。在这里,我们展示了一种新型钴催化剂可以克服这些挑战,为获得广泛的三取代烯烃提供有效和立体选择性的途径。该协议与单烯和二烯兼容,并表现出良好的官能团耐受性和可扩展性。而且,它已被证明是构建有机发光体和氘代三取代烯烃的有用工具。对该机制的初步研究表明,该反应涉及钴氢化物途径。该反应的高立体选择性归因于 π-π 堆积效应和底物和催化剂之间的空间位阻。
三取代烯烃的立体选择性合成是有机化学中长期存在的挑战,因为三取代烯烃的 E 和 Z 异构体之间的能量差异很小(与 1,2-二取代烯烃相比)。1,1-二取代烯烃的过渡金属催化异构化可以作为三取代烯烃的替代方法,但由于与反应效率和立体选择性有关的问题,它仍然不发达。在这里,我们展示了一种新型钴催化剂可以克服这些挑战,为获得广泛的三取代烯烃提供有效和立体选择性的途径。该协议与单烯和二烯兼容,并表现出良好的官能团耐受性和可扩展性。而且,它已被证明是构建有机发光体和氘代三取代烯烃的有用工具。对该机制的初步研究表明,该反应涉及钴氢化物途径。该反应的高立体选择性归因于 π-π 堆积效应和底物和催化剂之间的空间位阻。
The palladium-catalyzed synthesis of unsymmetrical 1,3-diarylpropenes from allyl esters through a Mizoroki–Heck-type reaction with aryl iodides followed by allyl cross-coupling with a variety of arylboronicacids was developed; the products are obtained in moderate to good yields by using a hydrazone–Pd(OAc)2 system.
<scp>Copper‐Catalyzed</scp>
Aerobic Oxidative Cleavage of Unstrained
<scp>Carbon‐Carbon</scp>
Bonds of 1,
<scp>1‐Disubstituted</scp>
Alkenes with Sulfonyl Hydrazides
carbon‐carbon bond cleavages have emerged as a powerful strategy to complement traditional ionic‐type transformations. However, carbon‐carbon cleavage reaction triggered by alkoxy radical intermediate derived from the combination of alkyl radical and dioxygen, is scarce and underdeveloped. Herein, we report alkoxy radical, which was generated from alkyl radical and dioxygen, mediated selective cleavage of unstrained
A photoredox/nickeldual catalyzed reductive hydrobenzylation of alkynes and benzyl chlorides by employing alkyl amines as a stoichiometric reductant is described. This synergistic protocol proceeds via Markovnikov-selective migratory insertion of an alkyne into nickel hydride, followed by cross-coupling with benzyl chloride, providing facile access to important 1,1-disubstituted olefins. This reaction
The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mechanism triggered strategy is developed by using Al(OTf)3 as a hidden Brønsted acid catalyst, which provides facile access to value-added acyclic tri- and tetra-substituted alkenes in good yields with high stereoselectivity under mild conditions. The practicality of this
Cross coupling of vinyl triflates and alkyl Grignard reagents catalyzed by nickel(0)-complexes
作者:Carl A. Busacca、Magnus C. Eriksson、Rita Fiaschi
DOI:10.1016/s0040-4039(99)00439-6
日期:1999.4
The scope and limitations of the Nickel(0)-catalyzed crosscoupling of vinyl triflates with alkyl Grignard reagents have been studied. The effect of triflate substitution, solvent, and especially ligands have been examined. Ligands which are successful for sp2 and sp Grignard reagents fail for sp3 Grignard reagents.