Decarboxylative Cyanation of Aliphatic Carboxylic Acids via Visible-Light Flavin Photocatalysis

Ramirez, Nieves P.; König, Burkhard; González-Gómez, José C.

doi:10.1021/acs.orglett.9b00064

Cited by 83 publications

(67 citation statements)

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“…dFl dF 0 in its oxidised form serves as a light-harvesting antenna in photolyases 29 . Inspired by nature, artificial Fl derivatives as well as flavoenzymes have been applied in photoredox catalysis and photobiocatalysis, mainly in oxidative transformations or in energy transfer processes 6,20,[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] . Photoenzymatic radical polymerisation employing highly reducing excited FADH* − known from photolyases is rare and a very recent example of a photoreductive process with Fl 45 .…”

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confidence: 99%

Deazaflavin reductive photocatalysis involves excited semiquinone radicals

et al. 2020

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Flavin-mediated photocatalytic oxidations are established in synthetic chemistry. In contrast, their use in reductive chemistry is rare. Deazaflavins with a much lower reduction potential are even better suited for reductive chemistry rendering also deazaflavin semiquinones as strong reductants. However, no direct evidence exists for the involvement of these radical species in reductive processes. Here, we synthesise deazaflavins with different substituents at C5 and demonstrate their photocatalytic activity in the dehalogenation of p-halogenanisoles with best performance under basic conditions. Mechanistic investigations reveal a consecutive photo-induced electron transfer via the semiquinone form of the deazaflavin as part of a triplet-correlated radical pair after electron transfer from a sacrificial electron donor to the triplet state. A second electron transfer from the excited semiquinone to p-halogenanisoles triggers the final product formation. This study provides first evidence that the reductive power of excited deazaflavin semiquinones can be used in photocatalytic reductive chemistry.

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Deazaflavin reductive photocatalysis involves excited semiquinone radicals

et al. 2020

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“…Consequently, the use of this reagent in the photoredox decarboxylation was postulated as a valuable alternative, which would avoid the addition of an oxidant. Such hypothesis was confirmed by the recently published decarboxylative cyanation of carboxylic acids based on the use of TsCN as reagent [20] and an inexpensive and non‐toxic derivative of vitamin B 2 as organic photocatalyst [21]…”

Section: Resultsmentioning

confidence: 79%

(Trifluoromethylselenyl)methylchalcogenyl as Emerging Fluorinated Groups: Synthesis under Photoredox Catalysis and Determination of the Lipophilicity

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Zordo-Banliat

Bourdreux

et al. 2021

Chemistry A European J

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The synthesis of molecules bearing (trifluoromethylselenyl)methylchalcogenyl groups is described via an efficient two‐step strategy based on a metal‐free photoredox catalyzed decarboxylative trifluoromethylselenolation with good yields up to 88 %, which raised to 98 % in flow chemistry conditions. The flow methods allowed also to scale up the reaction. The mechanism of this key reaction was studied. The physicochemical characterization of these emerging groups was performed by determining their Hansch–Leo lipophilicity parameters with high values up to 2.24. This reaction was also extended to perfluoroalkylselenolation with yields up to 95 %. Finally, this method was successfully applied to the functionalization of relevant bioactive molecules such as tocopherol or estrone derivatives.

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“…Selectfluor,– dibromoisocyanuric acid, t BuOCl, DIH, NIS and I 2 were employed for the synthesis of mono‐, di‐ and trifluoromethyl arenes, bromo‐, chloro‐ and iodo‐ methyl arenes. Decarboxylative trifluoromethylation, trifluoromethylthiolation cyanation and acetoxylation, were independently developed (Scheme ).…”

Section: Decarboxylationmentioning

confidence: 99%

Arylacetic Acids in Organic Synthesis

et al. 2019

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Arylacetic acids are widely used in organic reactions and their recent advances are summarized in six categories according to their triggered pathways: (1) the acid as directing group in ortho-or meta-CÀ H activation; (2) decarboxylation; (3) deprotonation; (4) nucleophilic methylenes; (5) nucleophilic acids; (6) electrophilic acids. Reactions with alkenes, alkynes, aldehydes, amines, water, Grignard reagents, silanes and so forth are discussed. We hope this Minireview will promote future research in this area. Recently, the Zeng group [3g] reported a weakly coordinationassisted alkynylation of arylacetic acids with iridium catalysis under air atmosphere (Eq. 2-2). It was supported the sixmembered ring cycloiridiated 2.5 acted as the key intermediate. The alkynylation of indole, thiophene, pyrrole, and benzo[b] thiophene afforded better yields than phenylacetic acids. The acid moiety could also participated in the intramolecular ortho-CÀ H activation, which was developed by the Shi group to obtain lactonization 2.6 (Eq. 2-3) (Scheme 2). Meta-CÀ H ArylationThe study of Yu group [3e] in 2017 revealed a successful control of meta selectivity 3.1 of arylation from aryl iodides (Eq. 3-1). The use of mono-protected 3-amino-2-hydroxypyridine (as ligand) and 2-carbomethoxynorbornene (NBE-CO 2 Me) were crucial. In the absence of NBE-CO 2 Me, only ortho-arylated product was obtained. This method was still efficient in a gramsale (Scheme 3). Decarboxylation Decarboxylative CouplingAs shown in Scheme 4, the decarboxylation could generate benzyl radicals 4.1. Then, direct couplings of 4.1 with diverse [ + ] These authors contributed equally. Scheme 1. Six categories based on triggered mechanism. 2 3 4 5 6 7 8 . Passerini Three-Component ReactionThe Passerini reaction was the oldest multicomponent reaction (MCR) [37d] in which isocyanides, carboxylic acids and aldehydes were used. It was powerful for the rapid construction of complex molecules. The tactic to expand the scope of Passerini reaction was to use surrogates of the carbonyl partners. As described in Scheme 51, syn-chlorooximes, [37b] diazoketones, [37c] alcohols, [37d,e] azirines [37f] and isatins [37g] could be employed instead of aryl or alkyl aldehydes [37a] (Scheme 51). Besides, in 2018, Zhang and co-workers [37] have firstly reported asymmetric phosphoric acid-catalyzed four-component Ugi reaction, which Scheme 45. BTM-catalyzed cycloaddition. Scheme 46. HBTM-catalyzed cycloaddition. Scheme 47. TFA-catalyzed reaction. Scheme 48. Friedel-Crafts triggered tandem reactions. Scheme 49. C-acylation of 1,3-diones. Scheme 50. C-acylation of 1,3-indandiones.

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Decarboxylative Cyanation of Aliphatic Carboxylic Acids via Visible-Light Flavin Photocatalysis

Cited by 83 publications

References 50 publications

Deazaflavin reductive photocatalysis involves excited semiquinone radicals

Deazaflavin reductive photocatalysis involves excited semiquinone radicals

(Trifluoromethylselenyl)methylchalcogenyl as Emerging Fluorinated Groups: Synthesis under Photoredox Catalysis and Determination of the Lipophilicity

Arylacetic Acids in Organic Synthesis

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