Borohydride reduction of acetophenone and esters of dehydrocarboxylic acids in the presence of chiral cobalt(II) diamine complexes

Nindakova, L. O.; Shainyan, B. А.

doi:10.1007/s11172-005-0258-8

Cited by 6 publications

(4 citation statements)

References 18 publications

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“…Thus, base metal catalysts that expand the range of substrates that can be hydrogenated with synthetically useful enantioselectivity would be valuable. While selected examples of asymmetric alkene hydrogenation are known, − H 2 is often not the stoichiometric reductant and the yields and selectivities are typically not synthetically useful. The discovery of high activity iron and cobalt complexes for alkene hydrogenation suggested that asymmetric variants should be within reach if appropriate chiral ligand architectures could be realized.…”

Section: Stereoselective Alkene Hydrogenation With Pyridine(diimine) ...mentioning

confidence: 99%

Iron- and Cobalt-Catalyzed Alkene Hydrogenation: Catalysis with Both Redox-Active and Strong Field Ligands

2015

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The hydrogenation of alkenes is one of the most impactful reactions catalyzed by homogeneous transition metal complexes finding application in the pharmaceutical, agrochemical, and commodity chemical industries. For decades, catalyst technology has relied on precious metal catalysts supported by strong field ligands to enable highly predictable two-electron redox chemistry that constitutes key bond breaking and forming steps during turnover. Alternative catalysts based on earth abundant transition metals such as iron and cobalt not only offer potential environmental and economic advantages but also provide an opportunity to explore catalysis in a new chemical space. The kinetically and thermodynamically accessible oxidation and spin states may enable new mechanistic pathways, unique substrate scope, or altogether new reactivity. This Account describes my group's efforts over the past decade to develop iron and cobalt catalysts for alkene hydrogenation. Particular emphasis is devoted to the interplay of the electronic structure of the base metal compounds and their catalytic performance. First generation, aryl-substituted pyridine(diimine) iron dinitrogen catalysts exhibited high turnover frequencies at low catalyst loadings and hydrogen pressures for the hydrogenation of unactivated terminal and disubstituted alkenes. Exploration of structure-reactivity relationships established smaller aryl substituents and more electron donating ligands resulted in improved performance. Second generation iron and cobalt catalysts where the imine donors were replaced by N-heterocyclic carbenes resulted in dramatically improved activity and enabled hydrogenation of more challenging unactivated, tri- and tetrasubstituted alkenes. Optimized cobalt catalysts have been discovered that are among the most active homogeneous hydrogenation catalysts known. Synthesis of enantiopure, C1 symmetric pyridine(diimine) cobalt complexes have enabled rare examples of highly enantioselective hydrogenation of a family of substituted styrene derivatives. Because improved hydrogenation performance was observed with more electron rich supporting ligands, phosphine cobalt(II) dialkyl complexes were synthesized and found to be active for the diastereoselective hydrogenation of various substituted alkenes. Notably, this class of catalysts was activated by hydroxyl functionality, representing a significant advance in the functional group tolerance of base metal hydrogenation catalysts. Through collaboration with Merck, enantioselective variants of these catalysts were discovered by high throughput experimentation. Catalysts for the hydrogenation of functionalized and essentially unfunctionalized alkenes have been discovered using this approach. Development of reliable, readily accessible cobalt precursors facilitated catalyst discovery and may, along with lessons learned from electronic structure studies, provide fundamental design principles for catalysis with earth abundant transition metals beyond alkene hydrogenation.

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Section: Stereoselective Alkene Hydrogenation With Pyridine(diimine) ...mentioning

confidence: 99%

Iron- and Cobalt-Catalyzed Alkene Hydrogenation: Catalysis with Both Redox-Active and Strong Field Ligands

2015

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“…Cobalt-containing complexes have been reported as effective catalysts for homogeneous hydrogenation. Studies by Pregaglia, 4 Ohgo, 5 Pfaltz, 6 Corma, 7 Shainyan, 8 Budzelaar, 9 Chirik, 10 Hanson, 11 and Peters 12 were reported to support the potential of ligand-assisted cobalt complex for the catalytic hydrogenation of olefinic compounds.…”

Section: ■ Introductionmentioning

confidence: 98%

Mechanistic Insights into the Directed Hydrogenation of Hydroxylated Alkene Catalyzed by Bis(phosphine)cobalt Dialkyl Complexes

Lei

2017

J. Org. Chem.

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The mechanism of directed hydrogenation of hydroxylated alkene catalyzed by bis(phosphine)cobalt dialkyl complexes has been studied by DFT calculations. The possible reaction channels of alkene hydrogenation catalyzed by catalytic species (0, 0, and 0) were investigated. The calculated results indicate that the preferred catalytic activation processes undergo a 1,2 alkene insertion. 0 and 0 prefer the β hydrogen elimination mechanism with an energy barrier of 9.5 kcal/mol, and 0 prefers the reductive elimination mechanism with an energy barrier of 11.0 kcal/mol. The second H coordination in the σ bond metathesis mechanism needs to break the agostic H-βC bond of metal-alkyl intermediates (2 and 2), which owns the larger energetic span compared to the reductive elimination. This theoretical study shows that the most favorable reaction pathway of alkene hydrogenation is the β hydrogen elimination pathway catalyzed by the planar (dppe)CoH. The hydrogenation activity of Co(II) compounds with redox-innocent phosphine donors involves the Co(0)-Co(II) catalytic mechanism.

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“…Unlike carbonyl reductions, which are now well demonstrated with a host of base-metal catalysts, , asymmetric alkene hydrogenations that operate with synthetically useful activities and enantioselectivities are much less developed. Cobalt catalysts for the net hydrogenation of alkenes have been known for some time, but substrate scope is limited, selectivities are generally low, and borohydride rather than hydrogen is used as the terminal reductant. − Our laboratory has reported C 1 -symmetric bis(imino)pyridine cobalt methyl complexes that are active for the hydrogenation of prochiral styrene derivatives with high enantioselectivity using H 2 as the stoichiometric reductant …”

Section: Introductionmentioning

confidence: 99%

Synthesis and Hydrogenation Activity of Iron Dialkyl Complexes with Chiral Bidentate Phosphines

et al. 2014

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The activity of bis(phosphine) iron dialkyl complexes for the asymmetric hydrogenation of alkenes has been evaluated. High-throughput experimentation was used to identify suitable iron−phosphine combinations using the displacement of pyridine from py 2 Fe(CH 2 SiMe 3 ) 2 for precatalyst formation. Preparative-scale synthesis of a family of bis(phosphine) iron dialkyl complexes was also achieved using both ligand substitution and salt metathesis methods. Each of the isolated organometallic iron complexes was established as a tetrahedral and hence high-spin ferrous compound, as determined by Mossbauer spectroscopy, magnetic measurements, and, in many cases, X-ray diffraction. One example containing a Josiphos-type ligand, (SL-J212-1)Fe(CH 2 SiMe 3 ) 2 , proved more active than other isolated iron dialkyl precatalysts. Filtration experiments and the lack of observed enantioselectivity support dissociation of the phosphine ligand upon activation with dihydrogen and formation of catalytically active heterogeneous iron. The larger six-membered chelate is believed to reduce the coordination affinity of the phosphine for the iron center, enabling metal particle formation.

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Borohydride reduction of acetophenone and esters of dehydrocarboxylic acids in the presence of chiral cobalt(II) diamine complexes

Cited by 6 publications

References 18 publications

Iron- and Cobalt-Catalyzed Alkene Hydrogenation: Catalysis with Both Redox-Active and Strong Field Ligands

Iron- and Cobalt-Catalyzed Alkene Hydrogenation: Catalysis with Both Redox-Active and Strong Field Ligands

Mechanistic Insights into the Directed Hydrogenation of Hydroxylated Alkene Catalyzed by Bis(phosphine)cobalt Dialkyl Complexes

Synthesis and Hydrogenation Activity of Iron Dialkyl Complexes with Chiral Bidentate Phosphines

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