Radical 1,2-addition of bromoarenes to alkynes <i>via</i> dual photoredox and nickel catalysis

Xu, Lei; Zhu, Shuaishuai; Huo, Liping; Chen, Fan; Yu, Wei; Chu, Lingling

doi:10.1039/d1qo00365h

Cited by 18 publications

(9 citation statements)

References 82 publications

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“…With the complexes in hand, control experiments to test the viability of Ni II adducts of 4-bromobenzotrifluoride (complex 73 ), bromobenzene (complex 74 ), and 3-bromotoluene (complex 75 ), which are electronically differentiated, were then carried out (Scheme A–C). , In contrast to previous studies, , bromobenzene and 3-bromotoluene were chosen instead of 2-bromotoluene to avoid the potential for either steric bias or influence of the latter. When complex 73 was used as a catalyst (6 mol %) to promote the coupling of 1 and 4-bromobenzotrifluoride, the decarboxylative arylated product 50a was obtained in 80% yield.…”

Section: Resultsmentioning

confidence: 99%

Metallaphotoredox Decarboxylative Arylation of Natural Amino Acids via an Elusive Mechanistic Pathway

et al. 2022

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The merger of photoredox and nickel catalysis for the decarboxylative arylation of carboxylic acids has evolved into an effective strategy to forge C–C bonds from readily available feedstock. Despite its rapid industrial adoption, the mechanism of this dual-catalyzed cross-coupling reaction has remained unclear and under-studied. Here, we propose an alternative mechanism for the photoredox–Ni dual-catalyzed decarboxylative arylation of α-amino acids based on control experiments with NiIIArBr complexes, cyclic voltammetry (CV), and computational studies. Our mechanistic studies revealed that a Ni0–NiII–NiI–NiII–Ni0 cycle is feasible in the dual-catalyzed Csp2 –Csp3 cross-coupling. Distinct from previous mechanism proposals, we show with a series of CV studies and density functional theory (DFT) calculations that a single electron transfer reduction of NiIIArBr to NiIAr by IrII is thermodynamically favorable. Reductive elimination via a NiII-species rather than via a NiIII-species is also supported by DFT calculations. Those mechanistic insights allowed for the reaction scope to be extended to encompass α-amino acids bearing pharmacophoric elements, which were previously unexplored coupling partners. α-Amino acids bearing broad functional groups, including heterocycles, successfully underwent decarboxylative arylation with a diverse set of aryl bromides. This strategy represents an advance in photoredox and Ni-catalysis and broadens its industrial applicability as well as mechanistic understanding.

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Section: Resultsmentioning

confidence: 99%

Metallaphotoredox Decarboxylative Arylation of Natural Amino Acids via an Elusive Mechanistic Pathway

et al. 2022

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“…In addition, 5 was obtained from the Heck reaction of 2 a with styrene in moderate yield with 94 % ee [18b] . Moreover, alkenyl borides 6 was obtained from the boronization of 2 a with 67 % yield in 95 % ee [18c] . Likewise, 7 was obtained in 94 % ee from the reduction of the alkenyl chloride [18d] .…”

Section: Resultsmentioning

confidence: 99%

Palladium‐Catalyzed Enantioselective Cyclization of 1,6‐Enynes through Intramolecular Chlorine Transfer as a Novel Strategy for Asymmetric Halopalladation

Tang

Zhang

et al. 2022

Chemistry A European J

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Palladium-catalyzed enantioselective cyclization of enynes has contributed significantly to the construction of chiral cyclic molecules. In contrast, the catalytic asymmetric cyclization involving halopalladation remains an unresolved challenge with the inevitable disturbance of the halide ions. Herein, an intramolecular chlorine transfer strategy is used to accomplish the enantioselective chloropalladation cyclization of 1,6-enynes. This reaction provides a redox-neutral approach to a variety of chiral α-chloromethylene-γ-butyrolactones with excellent E selectivity and enantioselectivity. The precisely controlled coordination of palladium with both the in situ generated nucleophilic species and the monodentate phosphoramidite ligand is crucial for enantioselectivity.

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“…To test the possibility of such a dual catalytic carbohalogenation reaction, we chose terminal alkyne 1 and bromostyrene 2 ( E/Z =8:1) as the template substrates (Table 1). We found that irradiation of reaction mixture of 1 and 2 with a 90 W Blue LED in the presence of catalytic Ir[dF(CF 3 )ppy] 2 (dtbbpy)PF 6 , NiBr 2 ⋅ DME, 4,4’‐di‐ tert ‐butyl‐2,2’‐bipyridine L1 (dtbbpy), and diisopropylamine (DIPA) afforded the desired bromo‐1,3‐dienes 3 and 4 in 19% and 21% yield, respectively (entry 1) [13c] . To improve the poor regioselectivity, which, we reasoned, could be deterred by migratory insertion step of alkynes into alkenylnickel species, [15] we further evaluated a series of ligands ( L1 – L6 ) and found that the use of bisoxazoline (BOX) ligands ( L5 – L6 ) led to higher regioselectivity, furnishing the formation of bromo‐1,3‐diene 3 as a single regioisomer with moderate yields (entries 2–6).…”

Section: Methodsmentioning

confidence: 99%

Metallaphotoredox‐Enabled Intermolecular Carbobromination of Alkynes with Alkenyl Bromides

Jiao

Fan

et al. 2022

Adv Synth Catal

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A regioselective intermolecular carbohalogenation of alkynes with alkenyl bromides enabled by dual photoredox and nickel catalysis is described. This dual protocol enables an atomeconomic access to a wide array of brominated 1,3dienes from simple starting materials. Broad substrate scope and high regioselectivity are observed. The synthetic utility has been demonstrated and preliminary mechanistic studies have been performed to elucidate the reaction pathway.

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Radical 1,2-addition of bromoarenes to alkynes via dual photoredox and nickel catalysis

Abstract: A regioselective, intermolecular 1,2-addition of aryl bromides to alkynes enabled by photocatalytic generation of bromine radicals via photoredox and nickel catalysis is reported. This mild and redox-neutral protocol tolerates a...

Cited by 18 publications

References 82 publications

Metallaphotoredox Decarboxylative Arylation of Natural Amino Acids via an Elusive Mechanistic Pathway

Metallaphotoredox Decarboxylative Arylation of Natural Amino Acids via an Elusive Mechanistic Pathway

Palladium‐Catalyzed Enantioselective Cyclization of 1,6‐Enynes through Intramolecular Chlorine Transfer as a Novel Strategy for Asymmetric Halopalladation

Metallaphotoredox‐Enabled Intermolecular Carbobromination of Alkynes with Alkenyl Bromides

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