Decarboxylative Giese‐Type Reaction of Carboxylic Acids Promoted by Visible Light: A Sustainable and Photoredox‐Neutral Protocol

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

doi:10.1002/ejoc.201601478

Cited by 71 publications

(57 citation statements)

References 57 publications

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“…Although the product was obtained in a synthetically useful yield (48 %), a significant decreased was observed compared to the reaction at 0.25 mmol (68 %) . Moreover, to show that the allyl moiety can also serve as a radical acceptor, we conducted the Giese decarboxylative alkylation using reaction conditions previously developed in our group . Under these conditions, when carboxylic acid 1d was employed, compound 6 was obtained in an unoptimized 45 % yield.…”

Section: Resultsmentioning

confidence: 99%

Direct Decarboxylative Allylation and Arylation of Aliphatic Carboxylic Acids Using Flavin‐Mediated Photoredox Catalysis

2019

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We describe herein a direct decarboxylative allylation of aliphatic carboxylic acids with allylsulfones using visible light and riboflavin tetraacetate (RFTA) as photocatalyst. The reaction proceeds at room temperature tolerating a wide range of functionalities, avoiding the use of external bases or additives. Mechanistic studies support that alkyl radicals are involved in the reaction and that a true photocatalytic cycle is operating. It is proposed that the carboxylic acid is deprotonated by [RFTA]·–, and the corresponding carboxylate acts as a reductive quencher of RFTA*, which after decarboxylation produces the alkyl radical. The methodology was adapted to prepare benzothiazoles substituted at C2, by reacting some carboxylic acids with 2‐(phenylsulfonyl)benzothiazole. The number of carboxylic acids suitable for this arylation was lower than for the allylation and this different reactivity was briefly commented.

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Section: Resultsmentioning

confidence: 99%

Direct Decarboxylative Allylation and Arylation of Aliphatic Carboxylic Acids Using Flavin‐Mediated Photoredox Catalysis

2019

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“…More specifically, the possibility of a mechanistic spectrum where the electronics of an α-substituent would control whether the cyclization proceeds through a radical or anionic pathway. Whereas photoredox Giese-type processes are established for α-carbonyl 28 and α-boryl 29 olefins, similar reactivity in more electron-rich olefins is not established. Thus, we evaluated the energetics of anionic and radical ring closure for a representative system, 1,1-diphenylethylene (Scheme 7).…”

Section: Discussionmentioning

confidence: 99%

Redox-Neutral Photocatalytic Cyclopropanation via Radical/Polar Crossover

et al. 2018

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A benchtop stable, bifunctional reagent for the redox-neutral cyclopropanation of olefins has been developed. Triethylammonium bis(catecholato)iodomethylsilicate can be readily prepared on multigram scale. Using this reagent in combination with an organic photocatalyst and visible light, cyclopropanation of an array of olefins, including trifluoromethyl- and pinacolatoboryl-substituted alkenes, can be accomplished in a matter of hours. The reaction is highly tolerant of traditionally reactive functional groups (carboxylic acids, basic heterocycles, alkyl halides, etc.) and permits the chemoselective cyclopropanation of polyolefinated compounds. Mechanistic interrogation revealed that the reaction proceeds via a rapid anionic 3- exo- tet ring closure, a pathway consistent with experimental and computational data.

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“…Most photoredox catalyzed, decarboxylative generations of carbon-centered radicals are based on the formation of "stabilized" α-amino [59][60][61][62][63][64][65] or benzyl [66][67][68][69][70] radical species. However, the generation of unstabilized alkyl radical species is also known [71][72][73][74]. Based on these observations and considerations, we attempted to use monochloroacetic acid as a precursor for cyclopropanation.…”

Section: Resultsmentioning

confidence: 99%

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

Vliet¹,

Leeuwen²,

Brouwer³

et al. 2020

Beilstein J. Org. Chem.

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Where monochloroacetic acid is widely used as a starting material for the synthesis of relevant groups of compounds, many of these synthetic procedures are based on nucleophilic substitution of the carbon chlorine bond. Oxidative or reductive activation of monochloroacetic acid results in radical intermediates, leading to reactivity different from the traditional reactivity of this compound. Here, we investigated the possibility of applying monochloroacetic acid as a substrate for photoredox catalysis with styrene to directly produce γ-phenyl-γ-butyrolactone. Instead of using nucleophilic substitution, we cleaved the carbon chlorine bond by single-electron reduction, creating a radical species. We observed that the reaction works best in nonpolar solvents. The reaction does not go to full conversion, but selectively forms γ-phenyl-γ-butyrolactone and 4-chloro-4-phenylbutanoic acid. Over time the catalyst precipitates from solution (perhaps in a decomposed form in case of fac-[Ir(ppy)3]), which was proven by mass spectrometry and EPR spectroscopy for one of the catalysts (N,N-5,10-di(2-naphthalene)-5,10-dihydrophenazine) used in this work. The generation of HCl resulting from lactone formation could be an additional problem for organometallic photoredox catalysts used in this reaction. In an attempt to trap one of the radical intermediates with TEMPO, we observed a compound indicating the generation of a chloromethyl radical.

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Decarboxylative Giese‐Type Reaction of Carboxylic Acids Promoted by Visible Light: A Sustainable and Photoredox‐Neutral Protocol

Cited by 71 publications

References 57 publications

Direct Decarboxylative Allylation and Arylation of Aliphatic Carboxylic Acids Using Flavin‐Mediated Photoredox Catalysis

Direct Decarboxylative Allylation and Arylation of Aliphatic Carboxylic Acids Using Flavin‐Mediated Photoredox Catalysis

Redox-Neutral Photocatalytic Cyclopropanation via Radical/Polar Crossover

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

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