A photocatalytic decarboxylative/defluorinative [4 + 3] annulation of <i>o</i>-hydroxyphenylacetic acids and trifluoromethyl alkenes: synthesis of fluorinated dihydrobenzoxepines

Chen, Haoguo; He, Yuwei; Zhou, Lei

doi:10.1039/c8qo00970h

Cited by 48 publications

(52 citation statements)

References 62 publications

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“…Capitalizing on readily formed benzyl-stabilized radicals from o-hydroxyphenyl acetic acids, in 2018, Zhou et al focused on a mental-free photocatalytic decarboxylative/defluorinative [4 + 3] annulation, which mainly relied on the fine-tuning reactivity of radical/nucleophilic intermediates (Scheme 45). 87 The observation of simple phenol 45-4 failed to give rise to C-O coupled product 45-5 was consistent with a photocatalytic decarboxylative radical-triggered cascade mechanism (control experiment A). Meanwhile, detection of gem-difluoroalkene 45-7 in the reaction of phenylacetic acid 45-6 and 45-1a further confirmed the above supposition (control experiment B).…”

Section: α-Tifluoromethyl Alkenesupporting

confidence: 62%

Multiple-fold C–F bond functionalization for the synthesis of (hetero)cyclic compounds: fluorine as a detachable chemical handle

Ge¹,

Chu²

2022

Org. Chem. Front.

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Section: α-Tifluoromethyl Alkenesupporting

confidence: 62%

Multiple-fold C–F bond functionalization for the synthesis of (hetero)cyclic compounds: fluorine as a detachable chemical handle

Ge¹,

Chu²

2022

Org. Chem. Front.

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“…The chloromethyl radical generation by photoredox catalysis is a useful strategy for cyclopropanation [58]. 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].…”

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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“…However, this protocol was limited to the synthesis of N-containing heterocyclic compounds because α-aminoalkyl radicals are necessary intermediates for both steps of C-F bond cleavage. In the combination of the photoredox catalysis and base-mediated S N V reaction, our group developed a photocatalytic decarboxylative/defluorinative [4 + 3] annulation of o-hydroxyphenylacetic acids and trifluoromethyl alkenes (Scheme 38) [90]. The first photocatalytic C-F bond cleavage of trifluoromethyl alkenes led to gem-difluoroalkenes, which were readily converted into fluorinated dihydrobenzoxepines by cleaving a second C-F bond in the presence of base.…”

Section: Trifluoromethyl Alkenesmentioning

confidence: 99%

Recent Advances in C-F Bond Cleavage Enabled by Visible Light Photoredox Catalysis

Zhou

2021

Molecules

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The creation of new bonds via C-F bond cleavage of readily available per- or oligofluorinated compounds has received growing interest. Using such a strategy, a myriad of valuable partially fluorinated products can be prepared, which otherwise are difficult to make by the conventional C-F bond formation methods. Visible light photoredox catalysis has been proven as an important and powerful tool for defluorinative reactions due to its mild, easy to handle, and environmentally benign characteristics. Compared to the classical C-F activation that proceeds via two-electron processes, radicals are the key intermediates using visible light photoredox catalysis, providing new modes for the cleavage of C-F bonds. In this review, a summary of the visible light-promoted C-F bond cleavage since 2018 was presented. The contents were classified by the fluorosubstrates, including polyfluorinated arenes, gem-difluoroalkenes, trifluoromethyl arenes, and trifluoromethyl alkenes. An emphasis is placed on the discussion of the mechanisms and limitations of these reactions. Finally, my personal perspective on the future development of this rapidly emerging field was provided.

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A photocatalytic decarboxylative/defluorinative [4 + 3] annulation of o-hydroxyphenylacetic acids and trifluoromethyl alkenes: synthesis of fluorinated dihydrobenzoxepines

Abstract: A photocatalytic decarboxylative/defluorinative [4 + 3] annulation of o-hydroxyphenylacetic acids and trifluoromethyl alkenes was developed. The reaction led to fluorinated dihydrobenzoxepines through two consecutive C–F substitutions in a CF3 group.

Cited by 48 publications

References 62 publications

Multiple-fold C–F bond functionalization for the synthesis of (hetero)cyclic compounds: fluorine as a detachable chemical handle

Multiple-fold C–F bond functionalization for the synthesis of (hetero)cyclic compounds: fluorine as a detachable chemical handle

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

Recent Advances in C-F Bond Cleavage Enabled by Visible Light Photoredox Catalysis

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