Enantioselective Cobalt-Catalyzed Transformations

Abstract

International audienc

Cobalt‐Catalyzed Asymmetric Hydrogenation of C=N Bonds Enabled by Assisted Coordination and Nonbonding Interactions

“…These advantages,a sw ell as their relatively small atomic radii and unique electronic properties,m ake them attractive and favorable for asymmetric hydrogenation. [10] Cobalt is the earliest researched Earth-abundant metal catalyst in the field of asymmetric hydrogenation, and has shown excellent enantioselectivities with both unfuctionalized and functionalized alkenes. [3a-d, 5a,b, 7a] Compared to other inexpensive transition metals,c obalt can partake in redox (Co 0 /Co II ,C o I /Co III )a nd redox-neutral (Co I and Co II )c atalytic cycles,a nd stably coordinate with both chiral N-and P-donor ligands,w hich has led, therefore, to cobalt being utilized in various enantioselective transformations.…”

Asymmetric Transfer and Pressure Hydrogenation with Earth‐Abundant Transition Metal Catalysts

“…Their relative abundance, ease of use, and lower toxicity, make them particularly intriguing for use as catalysts. [17][18][19][20] Indeed, iron, one of the Earth's most abundant and versatile metals, has been used to catalyze a variety of synthetic transformations such as reductions, eliminations, cyclizations, and many more. Cobalt, another inexpensive transition metal, has shown potential in various reactions, especially crosscouplings.…”

Next‐Generation D2‐Symmetric Chiral Porphyrins for Cobalt(II)‐Based Metalloradical Catalysis: Catalyst Engineering by Distal Bridging

“…[1,2] Despite significant advancements in this endeavor,g eneral strategies for addressing the enduring issues of controlling reactivity and selectivity in radical reactions,particularly enantioselectivity,remain to be uncovered. [4,5] In this context, Co II complexes of porphyrins,a s1 5e stable metalloradicals,h ave exhibited unusual efficiencyinradical activation of diazo compounds to generate the fundamentally new a-Co III -alkyl radicals A1 (Scheme 1A). [4,5] In this context, Co II complexes of porphyrins,a s1 5e stable metalloradicals,h ave exhibited unusual efficiencyinradical activation of diazo compounds to generate the fundamentally new a-Co III -alkyl radicals A1 (Scheme 1A).…”

“…Among recent progresses, [3] metalloradical catalysis (MRC), which explores the use of metalloradical complexes as open-shell catalysts for catalytically generating organic radical intermediates as well as controlling subsequent homolytic radical transformations,h as emerged as ac onceptually new approach. [4,5] In this context, Co II complexes of porphyrins,a s1 5e stable metalloradicals,h ave exhibited unusual efficiencyinradical activation of diazo compounds to generate the fundamentally new a-Co III -alkyl radicals A1 (Scheme 1A). [6] Ther esulting Co-stabilized C-centered radical intermediates can undergo radical addition to alkenes for generation of g-Co III -alkyl radicals (A2), which subsequently undergo intramolecular homolytic radical substitution (3-exotet radical cyclization) to produce cyclopropanes and regenerate the Co II -based metalloradicals.T he outcome of this Co II -based metalloradical catalysis (Co II -MRC) is the revelation of an unprecedented catalytic pathway for olefin cyclopropanation, and it operates by as tepwise radical mechanism (Scheme 1A).…”