Catalytic radical difluoromethoxylation of arenes and heteroarenes

Lee, Johnny W.; Zheng, Weijia; Morales‐Rivera, Cristian A.; Liu, Peng; Ngai, Ming‐Yu

doi:10.1039/c8sc05390a

Cited by 49 publications

(38 citation statements)

References 51 publications

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“…The electroneutral reagent 1h failed to produce the desired product under irradiation, which may due to the low reduction potential (E 1/2 red = −1.808 V vs SCE) (entry 8). This result validated the precedential presumption that the cationic reagent can serve as a better electron acceptor to furnish N-centered neutral radicals [48][49][50][51] . Other diboron reagents, such as bis(pinacolato)diboron (B 2 pin 2 ) and bis(neopentylglycolato)-diboron (B 2 neop 2 ), did not provide the corresponding borylated products (entries 9-10).…”

Section: Resultssupporting

confidence: 79%

Integrated redox-active reagents for photoinduced regio- and stereoselective fluorocarboborylation

et al. 2020

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Vinylboronates and alkylboronates are key components in variegated transformations in all facets of chemical science. The synthesis of vinylboronates and alkylboronates suffers from step-tedious and poor stereoselective procedures. We have developed a regulated radical difunctionalization strategy for the construction of fluorine-containing vinylboronates and alkylboronates with an integrated redox-active reagent IMDN-SO 2 R F. This bench-stable imidazolium sulfonate cationic salt offers a scalable and operational protocol for the fluoroalkylation-borylation of unsaturated hydrocarbons in a high regio-and stereoselective manner. The products can be further transformed into valuable fluorinated building blocks.

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Section: Resultssupporting

confidence: 79%

Integrated redox-active reagents for photoinduced regio- and stereoselective fluorocarboborylation

et al. 2020

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“…for 3b'a, NaOH is more effective than LiOH. Starting from readily available difluoroacetic acid, the reaction gives convenient and sustainable access to Ngai difluoromethoxylating reagents (3f′b-3f′d) 68 , which effectively promote the direct C-H difluoromethoxylation of (hetero)arenes. Tertiary carboxylic acids or those with a strong stabilising effect for the corresponding CCR (e.g.…”

Section: Resultsmentioning

confidence: 99%

Taking electrodecarboxylative etherification beyond Hofer–Moest using a radical C–O coupling strategy

et al. 2020

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Established electrodecarboxylative etherification protocols are based on Hofer-Moest-type reaction pathways. An oxidative decarboxylation gives rise to radicals, which are further oxidised to carbocations. This is possible only for benzylic or otherwise stabilised substrates. Here, we report the electrodecarboxylative radical-radical coupling of lithium alkylcarboxylates with 1-hydroxybenzotriazole at platinum electrodes in methanol/pyridine to afford alkyl benzotriazole ethers. The substrate scope of this electrochemical radical coupling extends to primary and secondary alkylcarboxylates. The benzotriazole products easily undergo reductive cleavage to the alcohols. They can also serve as synthetic hubs to access a wide variety of functional groups. This reaction prototype demonstrates that electrodecarboxylative CO bond formation can be taken beyond the intrinsic substrate limitations of Hofer-Moest mechanisms.

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“…The mechanistic hypothesis of the proposed transformation is outlined in Scheme 1. We envisioned that the reaction proceeds through an oxidative redox cycle beginning SET between di‐ or trifluoromethoxylating reagent 1 a ( E p =+0.11 V vs. SCE) [18g] or 1 b ( E p =+0.14 V vs. SCE) [18e] and TEMPO . ( E 1/2 =+0.62 V vs. SCE), [12b] generating 2,2,6,6‐tetramethyl‐1‐oxo‐1λ 4 ‐piperidine (TEMPO + ) and the di‐ or trifluoromethoxy radical ( .…”

Section: Figurementioning

confidence: 99%

Redox‐Neutral TEMPO Catalysis: Direct Radical (Hetero)Aryl C−H Di‐ and Trifluoromethoxylation

et al. 2020

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Applications of TEMPOC catalysis for the development of redox-neutral transformations are rare. Reported here is the first TEMPOC-catalyzed, redox-neutral CÀH di-and trifluoromethoxylation of (hetero)arenes. The reaction exhibits a broad substrate scope, has high functional-group tolerance, and can be employed for the late-stage functionalization of complex druglike molecules. Kinetic measurements, isolation and resubjection of catalytic intermediates, UV/Vis studies, and DFT calculations support the proposed oxidative TEMPOC/ TEMPO + redox catalytic cycle. Mechanistic studies also suggest that Li 2 CO 3 plays an important role in preventing catalyst deactivation. These findings will provide new insights into the design and development of novel reactions through redox-neutral TEMPOC catalysis. Figure 1. TEMPOC-catalyzed redox-neutral aryl CÀH functionalization.

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Catalytic radical difluoromethoxylation of arenes and heteroarenes

Abstract: The first visible light photocatalytic generation and utilization of the OCF2H radical for direct (hetero)aryl C–H difluoromethoxylation at room temperature.

Cited by 49 publications

References 51 publications

Integrated redox-active reagents for photoinduced regio- and stereoselective fluorocarboborylation

Integrated redox-active reagents for photoinduced regio- and stereoselective fluorocarboborylation

Taking electrodecarboxylative etherification beyond Hofer–Moest using a radical C–O coupling strategy

Redox‐Neutral TEMPO Catalysis: Direct Radical (Hetero)Aryl C−H Di‐ and Trifluoromethoxylation

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