Recent advances in dual transition metal–visible light photoredox catalysis

Tóth, Balázs L.; Tischler, Orsolya; Novàk, Zoltán

doi:10.1016/j.tetlet.2016.08.081

Cited by 71 publications

(21 citation statements)

References 110 publications

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“…In this scenario, one of the most promising approaches is developing cooperative photoredox-transition metal catalysis using organometallic catalysts incorporating earth abundant first row transition metals, such as nickel.7, 10,14,15 This combined photoredox-nickel dual catalysis has been proved to be an effective strategy for activating non-traditional cross-coupling nucleophiles. 10,11,16 Among the most notable examples is the decarboxylative coupling of aliphatic carboxylic acids with aryl-bromides, where an alkyl radical -generated by decarboxylative SET between the carboxylic acid and the Irphotocatalyst -is coupled with an aryl-bromide by the nickel complex.17-20 Other notable studies expanded this methodology to use benzyl potassium trifluoroborate salts,21-27 4-alkyl-1,4dihydropyridines,28 or potassium alkylbis(catecholato) silicates as radical precursors,29 and demonstrated broad functional group tolerance in the cross-coupling of different C(sp3)-radical precursors with aryl or vinyl halides. 30 These successful examples have shown that photoredox-Considering that this catalysis still is in its infancy, we decided to embark in a systematic computational study aimed at providing a comprehensive mechanistic scenario of a prototype reaction in the field.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino C_sp3–H Bonds

et al. 2020

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We report here a comprehensive computational analysis of the mechanisms of the photoredox-nickel-HAT (HAT: hydrogen atom transfer) catalyzed arylation and alkylation of αamino Csp3-H bonds developed by MacMillan and coworkers. Different alternatives for the three catalytic cycles were tested to identify unambiguously the operative reaction mechanism. Our analysis indicated that the IrIII photoredox catalyst, upon irradiation with visible light, can be either reduced or oxidized by the HAT and nickel catalysts, respectively, indicating that both reductive and oxidative quenching catalytic cycles can be operative, although the reductive cycle is favored. Our analysis of the HAT cycle indicated that activation of a -amino Csp3-H bond of the substrate is facile and selective relative to activation of a -amino Csp3-H bond. Finally, our analysis of the nickel cycle indicated that both arylation and alkylation of α-amino Csp3-H bonds occurs via the sequence of nickel oxidation states NiI-NiII-NiI-NiIII, and of elementary steps: radical addition-SET-oxidative addition-reductive elimination. transition metal catalysis can be a winning methodology to solve some of the challenges related to functionalization of Csp3-H bonds within C-C cross-coupling schemes.31-34 Recently, a strategy for the functionalization of α-amino Csp3-H bonds using photoredox catalysis, induced by visible-light in combination with a nickel and an organocatalyst, was reported by MacMillan and coworkers (Scheme 1).20, [35][36][37] In this protocol the organocatalyst acts as a hydrogen atom transfer, HAT, agent, generating an alkyl radical by selective activation of a α-amino Csp3-H bond. This merger has culminated in the ability to cross-couple alkyl radicals with metal-activated electrophiles, such as aryl and alkyl bromides, to forge new Csp3-Csp2 and Csp3-Csp3 bonds.Despite a large number of experimental papers in the field of photoredox-nickel dual catalysis, a comprehensive mechanistic picture of this chemistry is still missing. Focusing on theoretical studies, for C-N cross-coupling reaction it has been proposed that a Ni0 species, generated in situ, is the active coupling catalyst and the mechanism involves the modulation of the nickel oxidation state by SET from the photoredox catalyst, rather than by EnT.38 In contrast, for C-O cross-coupling it has been proposed that a NiI species is the active coupling catalyst.39 Different conclusions have been also proposed to explain formation of C-C bonds. In the case of the cross-coupling of aryl bromides with C-centered radicals derived from alkyltrifluoroborates it was proposed that a Ni0 species is the active coupling catalyst, with the Ni0-NiI-NiIII-NiI sequence of oxidation states.24 27, 40 Instead, for difunctionalization of alkynes to tri-substituted alkenes, an experimental and computational study indicated that NiI serves as the active catalyst.41 Scheme 1. Reactions and catalysts investigated in this work. The HAT catalyst Q is used for arylation reaction while Q' is used for alkylation reac...

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Section: Introductionmentioning

confidence: 99%

Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino C_sp3–H Bonds

et al. 2020

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“…1,2 This classical methodology has ushered in unprecedented opportunities for innovation, more recently, in the wake of visible-light mediated photoredox catalysis. 3–10 The last decade has witnessed the innovative merger of these two catalytic modes, 11–18 which is termed as metallaphotocatalysis, 18 for tackling some intractable problems. In this context, nickel catalysis, which was initially used as a cheaper alternative to noble metals in traditional cross-coupling reactions, 19 has played a more prominent role in this arena, 20–25 due to its ability to engage in single-electron transfer (SET), energy transfer (ET) or radical-capture reaction pathways.…”

Section: Introductionmentioning

confidence: 99%

A nickel/organoboron catalyzed metallaphotoredox platform for C(sp²)–P and C(sp²)–S bond construction

Zhu

Tian

et al. 2022

Org. Chem. Front.

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“…While describing such methodologies, difluoromethylation reactions of diverse families of organic substrates such as (hetero)aromatic compounds, olefins, [24,18] isocyanides, [17] alkynes, carbonyl compounds, [48,20] alcohols, hydrazones, tertiary amines,s ulfides, and azo compounds will be presented. The methodology described for such reactions will include metalmediated photocatalytic [50][51][52] and thermal processes, as well as metal-free methodologies. The two tables presented critically summarize all reagents employed either for late stage CF 2 H (Table 1) or CF 2 Y(Ta ble 2) group introductioninto organic compounds.…”

Section: Introductionmentioning

confidence: 99%

Difluoromethylation Reactions of Organic Compounds

Yerien

Barata‐Vallejo

Postigo

2017

Chemistry A European J

391

153

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The relevance of the -CF H moiety has attracted considerable attention from organic synthetic and medicinal chemistry communities, because this group can act as a more lipophilic isostere of the carbinol, thiol, hydroxamic acid, or amide groups. Being weakly acidic, the CF H moiety can establish hydrogen-bonding interactions to improve the binding selectivity of biologically active compounds. Therefore, the hydroxyl, amino, and thio substituents of lead structures are routinely replaced by a CF H motif in drug discovery, with great benefits in the pharmacological activity of drugs and drug candidates and agrochemicals. Consequently, the late-stage introduction of CF H is a sought-after strategy in designing bioactive compounds. Secondly, but nonetheless relevant and meaningful, is the study of synthetic pathways to introduce a CF -Y moiety (Y≠H, F) into organic substrates because compounds that contain a CF -Y functionality have also found vast applications in medicinal chemistry and in other areas, such as that of fungicides, insecticides, etc., and thus, this functionality deserves special attention. Although emphasis is made on difluoromethylation strategies to functionalize different families of organic compounds, three main methodological protocols will be presented in this review article for the late-stage introduction of a CF H or CF Y moieties into organic substrates: i) a metal-photoredox catalysis; ii) through transition metal-catalyzed thermal protocols; and iii) from transition-metal-free strategies.

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Recent advances in dual transition metal–visible light photoredox catalysis

Cited by 71 publications

References 110 publications

Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino C_sp3–H Bonds

Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino C_sp3–H Bonds

A nickel/organoboron catalyzed metallaphotoredox platform for C(sp²)–P and C(sp²)–S bond construction

Difluoromethylation Reactions of Organic Compounds

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Recent advances in dual transition metal–visible light photoredox catalysis

Cited by 71 publications

References 110 publications

Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino Csp3–H Bonds

Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino Csp3–H Bonds

A nickel/organoboron catalyzed metallaphotoredox platform for C(sp2)–P and C(sp2)–S bond construction

Difluoromethylation Reactions of Organic Compounds

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Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino C_sp3–H Bonds

Mechanistic Insight into the Photoredox-Nickel-HAT Triple Catalyzed Arylation and Alkylation of α-Amino C_sp3–H Bonds

A nickel/organoboron catalyzed metallaphotoredox platform for C(sp²)–P and C(sp²)–S bond construction