Enroute sustainability: metal free C–H bond functionalisation

Roy, Sayan; Panja, Subir; Sahoo, Sumeet Ranjan; Chatterjee, Sagnik

doi:10.1039/d0cs01466d

Cited by 30 publications

(15 citation statements)

References 326 publications

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“…5 could also be synthesized in a second synthetic procedure on small scales from the addition of LiInd to [{Rh(μ-Cl)(CO) 2 } 2 ], then by the subsequent addition of IDipp to the reaction mixture to yield 5. The carbonyl 13 C NMR signal was observed at 195.1 ppm with a 1 J Rh−C coupling of 92.3 Hz. The carbenic carbon was visible at 186.9 ppm with a 1 J Rh−C coupling of 72.5 Hz.…”

Section: Synthesis Of Cp Rh Complexes [Rhcp(coe) 2 ]mentioning

confidence: 99%

Catalyst Design for Rh-Catalyzed Arene and Alkane C–H Borylation: The NHC Affects the Induction Period, and Indenyl is Superior to Cp

Morton,

Boyce,

Pišpek

et al. 2024

Organometallics

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In order to establish design criteria for Rh C−H borylation catalysts, analogues of the successful catalyst [Rh(Ind)(SIDipp)(COE)] (Ind = η 5 -indenyl, SIDipp = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene, and COE = cis-cyclooctene) were synthesized by changing the indenyl and carbene ligands. [RhCp(SIDipp)-(COE)] (1) formed alongside the C−C activated, cyclometalated byproduct [RhCp-(κ 2 C Ar ,C carbene -SIDipp′)( i Pr)] (rac-2; SIDipp′ = 1-(6-isopropylphenyl)-3-(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene). Computational modeling of COE dissociation showed that both C−C and C−H activation of the SIDipp aryl group is thermally attainable and reversible under experimental conditions, with the C−C activation products being the more thermodynamically stable species. Oxidative addition of 1 with SiH(OEt) 3 gave the Rh silyl hydride [RhCp(H){Si(OEt) 3 }(SIDipp)] (rac-3). [Rh(Ind)(IDipp)(COE)] (4; IDipp = 1,3-bis(2,6-diisopropylphenyl)-imidazole-2ylidene), the carbonyl analogue [Rh(Ind)(IDipp)(CO)] (5; ν CO = 1940 cm −1 , cf. 1944 cm −1 for [Rh(Ind)(SIDipp)(COE)]), and [Rh(Ind)(IMe 4 )(COE)] ( 6; IMe 4 = 1,3,4,5-tetramethylimidazol-2-ylidene) were also characterized, but attempts to synthesize Rh carbene complexes with fluorenyl or 1,2,3,4-tetrahydrofluorenyl ligands were not successful. For the catalytic C−H borylation of benzene using B 2 pin 2 , 1 was inactive at 80 °C, and [Rh(Ind)(SIDipp)(COE)] was superior to all other complexes tested due to the shortest induction period. However, the addition of HBpin to precatalyst 4 eliminated the induction period. Catalytic n-alkane C−H borylation using [Rh(Ind)(NHC)(COE)] gave yields of up to 21% alkylBpin, but [RhCp*(C 2 H 4 ) 2 ] was the better catalyst.

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Section: Synthesis Of Cp Rh Complexes [Rhcp(coe) 2 ]mentioning

confidence: 99%

Catalyst Design for Rh-Catalyzed Arene and Alkane C–H Borylation: The NHC Affects the Induction Period, and Indenyl is Superior to Cp

Morton,

Boyce,

Pišpek

et al. 2024

Organometallics

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“…The activation of inert C–H bonds has been a challenging reaction for the functionalization of organic compounds in many chemical and pharmaceutical industries. − In the biological system, high-valent metal–(hydr)oxo species have been invoked in a variety of metalloenzymes as a remarkable class of intermediates that cleave and functionalize strong C–H bonds through a hydrogen atom transfer (HAT) mechanism. − To date, through synthetic model chemistry, the mechanism of the C–H bond activation by metal oxido complexes has actively been discussed with regard to driving forces of the HAT between the C–H bond being cleaved and the O–H bond being formed. − The paradigm of thermodynamics on bond dissociation free energies (BDFEs) renders multiple mechanisms for the HAT involving (synchronous or asynchronous) proton-coupled electron transfer (PCET), and stepwise proton–electron transfer (PT/ET), or electron–proton transfer (ET/PT). These studies have expanded our understanding of the behavior of various catalysts involved in the C–H bond functionalization.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization, and Reactivity of a Highly Oxidative Mononuclear Manganese(IV)–Bis(Fluoro) Complex

Jeong,

Lee,

Lee

et al. 2024

J. Am. Chem. Soc.

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Recently, transition-metal terminal nonoxo complexes have shown a remarkable ability to activate and functionalize C−H bonds via proton-coupled electron transfer (PCET). Here we report the first example of a mononuclear manganese(IV) bis(fluoro) complex bearing a tetradentate pyridinophane ligand, [Mn IV (TBDAP)(F) 2 ] 2+ (3), with an X-ray single crystal structure and physicochemical characterization. The manganese(IV) bis(fluoro) complex has a very high reduction potential of 1.61 V vs SCE, thereby enabling the four-electron oxidation of mesitylene to 3,5-dimethylbenzaldehyde. Kinetic studies, including the kinetic isotope effect and employment of other toluene derivatives, reveal the electron transfer (ET)-driven PCET in the C−H bond activation of mesitylene by 3. This novel metal halide intermediate would be prominently valuable for expanding transition-metal halide chemistry.

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“…Modern C–H functionalization chemistries have introduced late-stage functionalization (LSF) strategies in medicinal chemistry, targeting drug lead C–H bonds for creating new analogues. This toolbox includes photoredox-mediated and radical reactions and among them, amination reactions for the direct formation of C–N bonds. , Recently, the focus is shifting from metal to organocatalytic protocols, paving the way to sustainability and adhering to green chemistry principles to minimize waste and improve yield and atom economy . This approach aligns with the EU’s sustainable development policy. , Numerous research groups are exploring new C(sp 3 )-H functionalization reactions with high chemo-, regio-, and stereoselectivity.…”

Section: Introductionmentioning

confidence: 99%

Regioselective Rearrangement of Nitrogen- and Carbon-Centered Radical Intermediates in the Hofmann–Löffler–Freytag Reaction

Zubčić,

You,

Zott

et al. 2024

J. Phys. Chem. A

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The Hofmann−Loffler−Freytag (HLF) reaction serves as a late-stage functionalization technique for generating pyrrolidine heterocyclic ring systems. Contemporary HLF protocols utilize in situ halogenated sulfonamides as precursors in the radical-mediated rearrangement cycle. Despite its well-established reaction mechanism, experiments toward the detection of radical intermediates using EPR techniques have only recently been attempted. However, the obtained spectra lack the distinct features of the Ncentered radicals expected for the employed reactants. This paper presents phenylbutylnitrone spin-trapped C-centered and N-centered radicals, generated via light irradiation from N-halogen-tosyl-sulfonamide derivatives and detected using EPR spectroscopy. NMR spectroscopy and DFT calculations are used to explain the observed regioselectivity of the HLF reaction.

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Enroute sustainability: metal free C–H bond functionalisation

Abstract: The metal-free C–H functionalisation is providing environmentally benign, cost-effective, sustainable catalytic systems. Comprehensive developments of various metal-free C–H functionalisation reactions are the focal point of this review.

Cited by 30 publications

References 326 publications

Catalyst Design for Rh-Catalyzed Arene and Alkane C–H Borylation: The NHC Affects the Induction Period, and Indenyl is Superior to Cp

Catalyst Design for Rh-Catalyzed Arene and Alkane C–H Borylation: The NHC Affects the Induction Period, and Indenyl is Superior to Cp

Synthesis, Characterization, and Reactivity of a Highly Oxidative Mononuclear Manganese(IV)–Bis(Fluoro) Complex

Regioselective Rearrangement of Nitrogen- and Carbon-Centered Radical Intermediates in the Hofmann–Löffler–Freytag Reaction

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