Copper–Carbon Homolysis Competes with Reductive Elimination in Well-Defined Copper(III) Complexes

Yan, Wenhao; Carter, Samantha; Hsieh, Chi-Tien; Krause, Jeanette A.; Cheng, Mu-Jeng; Zhang, Shiyu; Liu, Wei

doi:10.1021/jacs.3c08510

Cited by 16 publications

(3 citation statements)

References 63 publications

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“…We have assigned complex 4 as a neutral benzyl–Cu III –(CF 3 ) 2 given that a similar species has been synthesized in our prior study via the selective removal of a CF 3 group from a tetra-coordinate and anionic Cu III species . In good agreement with the previous work, compound 4 formed via oxidative addition decomposed rapidly, via a reductive elimination pathway, even at low temperatures (Figure S1).…”

Section: Resultssupporting

confidence: 90%

“…Contrastingly, in complexes 5 and 5b – 5f , the CH 2 groups resonate at higher frequencies, e.g., 4.08 and 3.45 ppm for 5 and 5d , respectively. Notably, the CH 2 protons in our previously reported four-coordinate and anionic complex, PPh 4 [(CF 3 ) 3 Cu(CH 2 C 6 F 5 )], resonate at a lower frequency (2.85 ppm) . In addition, the CH 2 protons in the related Au III complexes, [(IPr)Au III (CF 3 ) 2 (CH 2 R)], reported by Toste, resonate at the range of ∼1.5 (R = CH 3 ) to 2.5 (R = alkenyl) ppm .…”

Section: Resultsmentioning

confidence: 70%

“…These EPR results are consistent with the formation of a four-coordinate complex, [Cu II (CH 3 CN) 2 (CF 3 ) 2 ] 6 . Notably, the formation of this species has been indicated in our recently reported Cu III –C bond homolysis process …”

Section: Resultsmentioning

confidence: 99%

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Catalytically Relevant Organocopper(III) Complexes Formed through Aryl-Radical-Enabled Oxidative Addition

Yan,

Poore,

Yin

et al. 2024

J. Am. Chem. Soc.

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Stepwise oxidative addition of copper(I) complexes to form copper(III) species via single electron transfer (SET) events has been widely proposed in copper catalysis. However, direct observation and detailed investigation of these fundamental steps remain elusive owing largely to the typically slow oxidative addition rate of copper(I) complexes and the instability of the copper(III) species. We report herein a novel aryl-radical-enabled stepwise oxidative addition pathway that allows for the formation of well-defined alkyl–CuIII species from CuI complexes. The process is enabled by the SET from a CuI species to an aryl diazonium salt to form a CuII species and an aryl radical. Subsequent iodine abstraction from an alkyl iodide by the aryl radical affords an alkyl radical, which then reacts with the CuII species to form the alkyl–CuIII complex. The structure of resultant [(bpy)CuIII(CF3)2(alkyl)] complexes has been characterized by NMR spectroscopy and X-ray crystallography. Competition experiments have revealed that the rate at which different alkyl iodides undergo oxidative addition is consistent with the rate of iodine abstraction by carbon-centered radicals. The CuII intermediate formed during the SET process has been identified as a four-coordinate complex, [CuII(CH3CN)2(CF3)2], through electronic paramagnetic resonance (EPR) studies. The catalytic relevance of the high-valent organo-CuIII has been demonstrated by the C–C bond-forming reductive elimination reactivity. Finally, localized orbital bonding analysis of these formal CuIII complexes indicates inverted ligand fields in σ(Cu–CH2) bonds. These results demonstrate the stepwise oxidative addition in copper catalysis and provide a general strategy to investigate the elusive formal CuIII complexes.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 70%

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Catalytically Relevant Organocopper(III) Complexes Formed through Aryl-Radical-Enabled Oxidative Addition

Yan,

Poore,

Yin

et al. 2024

J. Am. Chem. Soc.

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High‐Valent Copper Catalysis Enables Regioselective Fluoroarylation of Gem‐Difluorinated Cyclopropanes

Wu,

Song,

Xia

2024

Advanced Science

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Transition‐metal (TM) catalyzed reaction of gem‐difluorinated cyclopropanes (gem‐DFCPs) has drawn much attention recently. The reaction generally occurs via the activation of the distal C─C bond in gem‐DFCPs by a low‐valent TM through oxidative addition, eventually producing mono‐fluoro olefins as the coupling products. However, achieving regioselective activation of the proximal C─C bond in gem‐DFCPs that overcomes the intrinsic reactivity via TM catalysis remains elusive. Here, a new reaction mode of gem‐DFCPs enabled by high‐valent copper catalysis, which allows exclusive activation of the congested proximal C─C bond is presented. The reaction that achieves fluoroarylation of gem‐DFCPs uses NFSI (N‐fluorobenzenesulfonimide) as electrophilic fluoro reagent and arenes as the C─H nucleophiles, enabling the synthesis of diverse CF3‐containing scaffolds. It is proposed that a high‐valent copper species plays an important role in the regioselective activation of the proximal C─C bond possibly via a σ‐bond metathesis.

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Site‐Specific Deaminative Trifluoromethylation of Aliphatic Primary Amines**

Xue,

Li,

Liu

et al. 2024

Angewandte Chemie

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The introduction of trifluoromethyl groups into organic molecules is of paramount importance in modern synthetic chemistry and medicinal chemistry. While methods for constructing C(sp2)‐CF3 bonds have been well established, the advancement of practical and comprehensive approaches for forming C(sp3)‐CF3 bonds remains considerably restricted. In this work, we describe an efficient and site‐specific deaminative trifluoromethylation reaction of aliphatic primary amines to afford the corresponding alkyl trifluoromethyl compounds. The reaction proceeds at room temperature with readily accessible N‐anomeric amide (Levin’s reagent) and bench‐stable bpyCu(CF3)3 (Grushin’s reagent) under blue light. The protocol features mild reaction conditions, good functional group tolerance, and moderate to good yields. Remarkably, the method can be applied to the direct, late‐stage trifluoromethylation of natural products and bioactive molecules. Experimental mechanistic studies were conducted, and a radical mechanism is proposed, wherein the dual roles of Grushin’s reagent have been elucidated.

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Copper–Carbon Homolysis Competes with Reductive Elimination in Well-Defined Copper(III) Complexes

Cited by 16 publications

References 63 publications

Catalytically Relevant Organocopper(III) Complexes Formed through Aryl-Radical-Enabled Oxidative Addition

Catalytically Relevant Organocopper(III) Complexes Formed through Aryl-Radical-Enabled Oxidative Addition

High‐Valent Copper Catalysis Enables Regioselective Fluoroarylation of Gem‐Difluorinated Cyclopropanes

Site‐Specific Deaminative Trifluoromethylation of Aliphatic Primary Amines**

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