782-05-8Relevant articles and documents
Olefin functionalization/isomerization enables stereoselective alkene synthesis
Gutierrez, Osvaldo,Koh, Ming Joo,Liu, Chen-Fei,Martin, Robert T.,Wang, Hongyu,Zhao, Haonan
, p. 674 - 683 (2021/08/06)
Despite tremendous efforts aimed at devising methods for stereoselective alkene synthesis, critical challenges are yet to be addressed. Direct access to a diverse range of 1-aryl(boryl)-1-methyl-functionalized tri- and tetrasubstituted trans alkenes, entities that are prevalent in many important molecules, through a catalytic manifold from readily available α-olefin substrates remains elusive. Here, we demonstrate that catalytic amounts of a non-precious N-heterocyclic carbene–Ni(I) complex in conjunction with a sterically bulky base promote site- and trans-selective union of monosubstituted olefins with a wide array of electrophilic reagents to deliver tri- and tetrasubstituted alkenes in up to 92% yield and >98% regio- and stereoselectivity. The protocol is amenable to the preparation of carbon- and heteroatom-substituted C=C bonds, providing distinct advantages over existing transformations. Utility is highlighted through concise stereoselective synthesis of biologically active compounds. [Figure not available: see fulltext.].
Cathodic reductive couplings and hydrogenations of alkenes and alkynes catalyzed by the B12 model complex
Shimakoshi, Hisashi,Luo, Zhongli,Tomita, Kazuya,Hisaeda, Yoshio
, p. 71 - 77 (2017/05/08)
The reductive coupling and hydrogenation of alkenes were catalyzed by the B12 model complex, heptamethyl cobyrinate perchlorate (1), in the presence of acid during electrolysis at??0.7?V vs. Ag/AgCl in acetonitrile. Conjugated alkenes showed a good reactivity during electrolysis to form reduced products. The product distributions were dependent on the substituents at the C[dbnd]C bond of the alkenes. ESR spin-trapping experiments using 5,5-dimethylpyrroline N-oxide (DMPO) revealed that the cobalt-hydrogen complex (Co–H complex) should be formed during the electrolysis and it functioned as an intermediate for the alkene reduction. The electrolysis was also applied to an alkyne, such as phenylacetylene, to form 2,3-diphenylbutane (racemic and meso) and ethylbenzene via styrene as reductive coupling and hydrogenated products, respectively.
A heterobimetallic complex featuring a Ti-Co multiple bond and its application to the reductive coupling of ketones to alkenes
Wu, Bing,Bezpalko, Mark W.,Foxman, Bruce M.,Thomas, Christine M.
, p. 2044 - 2049 (2015/03/04)
To explore metal-metal multiple bonds between first row transition metals, Ti/Co complexes supported by two phosphinoamide ligands have been synthesized and characterized. The Ti metalloligand Cl2Ti(XylNPiPr2)2 (1) was treated with CoI2 under reducing conditions, permitting isolation of the Ti/Co complex [(μ-Cl)Ti(XylNPiPr2)2CoI]2 (2). One electron reduction of complex 2 affords ClTi(XylNPiPr2)2CoPMe3 (3), which features a metal-metal triple bond and an unprecedentedly short Ti-Co distance of 2.0236(9) ?. This complex is shown to promote the McMurry coupling reaction of aryl ketones into alkenes, with concomitant formation of the tetranuclear complex [Ti(μ3-O)(NXylPiPr2)2CoI]2 (4). A cooperative mechanism involving bimetallic C=O bond activation and a cobalt carbene intermediate is proposed.
