Recent Advances in Enantioselective C–C Bond Formation via Organocobalt Species

Yoshikai, Naohiko

doi:10.1055/s-0037-1610397

Cited by 30 publications

(5 citation statements)

References 36 publications

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“…Recently, earth-abundant metal catalysts for selective alkyne hydrosilylation are more attractive due to their low cost, long-term sustainability, and low toxicity . Our group has been interested in the discovery of new cobalt-catalyzed transformations. , Although a variety of Co-based catalysts have been revealed in hydrosilylation of simple alkynes and 1,3-enynes in high site- and stereoselectivity (Scheme a), single Si–H addition was exclusively involved in these processes. Cascade reactions of two Si–H bonds sequentially to a single unsaturated molecule in high chemo-, site-, and stereoselectivity remains unknown.…”

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confidence: 99%

Cobalt-Catalyzed Sequential Site- and Stereoselective Hydrosilylation of 1,3- and 1,4-Enynes

Zhao

Meng

2022

J. Am. Chem. Soc.

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Catalytic sequential hydrosilylation of 1,3-enynes and 1,4-enynes promoted by cobalt complexes derived from bisphosphines are presented. Site- and stereoselective Si–H addition of primary silanes to 1,3-enynes followed by sequential intramolecular diastereo- and enantioselective Si–H addition afforded enantioenriched cyclic alkenylsilanes with simultaneous construction of a carbon-stereogenic center and a silicon-stereogenic center. Reactions of 1,4-enynes proceeded through sequential isomerization of the alkene moiety followed by site- and stereoselective hydrosilylation. A wide range of alkenylsilanes were afforded in high efficiency and selectivity. Functionalization of the enantioenriched silanes containing a stereogenic center at silicon delivered a variety of chiral building blocks that are otherwise difficult to access.

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confidence: 99%

Cobalt-Catalyzed Sequential Site- and Stereoselective Hydrosilylation of 1,3- and 1,4-Enynes

Zhao

Meng

2022

J. Am. Chem. Soc.

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“…We reasoned that cobalt might lead to better selectivities in reactions of dienes by reducing the number of possible intermediates in the catalytic cycle (Figure E; see later Figure B for full details of a possible mechanism). These expectations have been borne out and the explorations that followed have evolved over the past few years as we recognized the unique role of Co(I) complexes, especially the cationic complexes, in catalyzing not only heterodimerization reactions, but also cycloaddition and hydrofunctionalization reactions of alkenes and alkynes …”

Section: Nickel-catalyzed Asymmetric Hydrovinylationmentioning

confidence: 99%

A New Paradigm in Enantioselective Cobalt Catalysis: Cationic Cobalt(I) Catalysts for Heterodimerization, Cycloaddition, and Hydrofunctionalization Reactions of Olefins

et al. 2021

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Conspectus One of the major challenges facing organic synthesis in the 21st century is the utilization of abundantly available feedstock chemicals for fine chemical synthesis. Regio- and enantioselective union of easily accessible 1,3-dienes and other feedstocks like ethylene, alkyl acrylates, and aldehydes can provide valuable building blocks adorned with latent functionalities for further synthetic elaboration. Through an approach that relies on mechanistic insights and systematic examination of ligand and counterion effects, we developed an efficient cobalt-based catalytic system [(P∼P)CoX2/Me3Al] (P∼P = bisphosphine) to effect the first enantioselective heterodimerization of several types of 1,3-dienes with ethylene. In addition to simple cyclic and acyclic dienes, siloxy-1,3-dienes participate in this reaction, giving highly functionalized, nearly enantiopure silyl enolates, which can be used for subsequent C–C and C–X bond-forming reactions. As our understanding of the mechanism of this reaction improved, our attention was drawn to more challenging partners like alkyl acrylates (one of the largest volume feedstocks) as the olefin partners instead of ethylene. Prompted by the intrinsic limitations of using aluminum alkyls as the activators for this reaction, we explored the fundamental chemistry of the lesser known (P∼P)Co(I)X species and discovered that in the presence of halide sequestering agents, such as sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBARF) or (C6F5)3B, certain chiral bisphosphine complexes are superb catalysts for regio- and enantioselective heterodimerization of 1,3-dienes and alkyl acrylates. We have since found that these cationic Co(I) catalysts, most conveniently prepared in situ by reduction of the corresponding cobalt(II) halide complexes by zinc in the presence of NaBARF, promote enantioselective [2 + 2]-cycloaddition between alkynes and an astonishing variety of alkenyl derivatives to give highly functionalized cyclobutenes. In reactions between 1,3-enynes and ethylene, the [2 + 2]-cycloaddition between the alkyne and ethylene is followed by a 1,4-addition of ethylene in a tandem fashion to give nearly enantiopure cyclobutanes with an all-carbon quaternary center, giving a set of molecules that maps well into many medicinally relevant compounds. In another application, we find that the cationic Co(I)-catalysts promote highly selective hydroacylation and 1,2-hydroboration of prochiral 1,3-dienes. Further, we find that a cationic Co(I)-catalyst promotes cycloisomerization followed by hydroalkenylation of 1,6-enynes to produce highly functionalized carbo- and heterocyclic compounds. Surprisingly the regioselectivity of the alkene addition depends on whether it is a simple alkene or an acrylate, and the acrylate addition produces an uncommon Z-adduct. This Account will provide a summary of the enabling basic discoveries and the attendant developments that led to the unique cationic Co(I)-complexes as catalysts for disparate C–C and C–B bond-forming reactions. It...

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“…Cobalt, a cheap and biocompatible 3d-metal, recently was found to exhibit excellent catalytic activity in asymmetric coupling reactions . In 2021, Xia and co-workers realized an ingenious reductive coupling reaction between alkynes and aldehydes via photoredox/cobalt dual catalysis for synthesizing allyl alcohols with high regio- and enantioselectivities .…”

Section: Introductionmentioning

confidence: 99%

Photoassisted Cobalt-Catalyzed Asymmetric Reductive Grignard-Type Addition of Aryl Iodides

Jiang

Yang

et al. 2022

J. Am. Chem. Soc.

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Grignard addition is one of the most important methods used for syntheses of alcohol compounds and has been known for over a hundred years. However, research on asymmetric catalysis relies on the use of organometallic nucleophiles. Here, we report the first visible-light-induced cobalt-catalyzed asymmetric reductive Grignard-type addition for synthesizing chiral benzyl alcohols (>50 examples, up to 99% yield, and 99% ee). This methodology has the advantages of mild reaction conditions, good functionality tolerance, excellent enantiocontrol, the avoidance of mass metal wastes, and the use of precious metal catalysts. Kinetic realization studies suggested that migratory insertion of an aryl cobalt species into the aldehyde was the rate-determining step of the reductive addition reaction.

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Recent Advances in Enantioselective C–C Bond Formation via Organocobalt Species

Cited by 30 publications

References 36 publications

Cobalt-Catalyzed Sequential Site- and Stereoselective Hydrosilylation of 1,3- and 1,4-Enynes

Cobalt-Catalyzed Sequential Site- and Stereoselective Hydrosilylation of 1,3- and 1,4-Enynes

A New Paradigm in Enantioselective Cobalt Catalysis: Cationic Cobalt(I) Catalysts for Heterodimerization, Cycloaddition, and Hydrofunctionalization Reactions of Olefins

Photoassisted Cobalt-Catalyzed Asymmetric Reductive Grignard-Type Addition of Aryl Iodides

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