Cobalt-Catalyzed Migrational Isomerization of Styrenes
摘要:
An efficient cobalt-catalyzed migrational isomerization of styrenes was developed using the thiazoline iminopyridine (TIP) ligand. This reaction is operationally simple and atom economical using readily available starting materials to access trisubstituted alkenes. Even when using a 0.1 mol % catalyst loading, the reaction could be conducted in neat and completed in 1 h with excellent conversion and high E stereoselectivity.
Iron catalyzed methylation and ethylation of vinyl arenes
作者:Nengbo Zhu、Jianguo Zhao、Hongli Bao
DOI:10.1039/c6sc04274k
日期:——
Short alkyl chain Heck (type) reactions, especially methyl Heck reactions, are a difficult aspect of the alkyl Heck reaction. To provide a solution to this problem, iron-catalyzed methyl, ethyl and propyl Heck reactions were developed using readily available alkyl peroxides as alkyl sources. The reaction conditions were mild, clean, and easy to handle. No additive was needed, and no hazardous waste
Cobalt(II)-Catalyzed Stereoselective Olefin Isomerization: Facile Access to Acyclic Trisubstituted Alkenes
作者:Sheng Zhang、Deepika Bedi、Lu Cheng、Daniel K. Unruh、Guigen Li、Michael Findlater
DOI:10.1021/jacs.0c02101
日期:2020.5.13
Stereoselective synthesis of trisubstitutedalkenes is a long-standing challenge in organic chemistry, due to the small energy differences between E and Z isomers of trisubstitutedalkenes (compared with 1,2-disubstituted alkenes). Transition metal-catalyzed isomerization of 1,1-disubstituted alkene can serve as an alternative approach to trisubsti-tuted alkenes, but it remains underdeveloped owing
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。
Regioselective Diboron-Mediated Semireduction of Terminal Allenes
作者:Ashley M. Gates、Webster L. Santos
DOI:10.1055/s-0039-1690207
日期:2019.12
A method for the regioselective reduction of the terminaldoublebond of 1,1-disubstituted allenes has been developed. In the presence of a palladium catalyst, tetrahydroxydiboron and stoichiometric water, allene semireduction proceeds in high yield to afford Z-alkenes selectively.
Triarylphosphine Ligands with Hemilabile Alkoxy Groups: Ligands for Nickel(II)-Catalyzed Olefin Dimerization Reactions. Hydrovinylation of Vinylarenes, 1,3-Dienes, and Cycloisomerization of 1,6-Dienes
作者:Souvagya Biswas、Aibin Zhang、Balaram Raya、T. V. RajanBabu
DOI:10.1002/adsc.201400237
日期:2014.7.7
practical synthesis of these compounds. In sharp contrast, hydrovinylation of a variety of 1,3‐dienes is best catalyzed by nickel(II) complexes of 2‐benzyloxyphenyldiphenylphosphine, L5. The other two ligands, 2‐benzyloxymethyl‐ (L6) and 2‐benzyloxyethyldiphenylphosphine (L7) are much less effective in the HV of 1,3‐dienes. Nickel(II)‐catalyzed cycloisomerization of 1,6‐dienes into methylenecyclopentanes
Iron Catalyzed Isomerization of
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Styrenes to Access Trisubstituted Alkenes
作者:Songgen Xu、Guixia Liu、Zheng Huang
DOI:10.1002/cjoc.202000492
日期:2021.3
supported by phosphine‐pyridine‐oxazoline (PPO) ligand. The protocol provides an atom‐efficient and operationally simple approach to trisubstituted alkenes in high yields with excellent regio‐ and stereoselectivities under mild conditions. The results of deuterium‐labelling and radical trap experiments are consistent with an iron‐hydride pathway involving reversible alkene insertion and β‐H elimination.