Carbonate-promoted C–H carboxylation of electron-rich heteroarenes

Porter, Tyler M.; Kanan, Matthew W.

doi:10.1039/d0sc04548a

Cited by 16 publications

(7 citation statements)

References 44 publications

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“…The observation of benzothiophene-3-carboxylate at low Cs 2 CO 3 loadings on TiO 2 is consistent with a separate electrophilic aromatic substitution mechanism for the carboxylation that is promoted by the TiO 2 surface. We previously observed that carboxylation at the most nucleophilic position is favored for more electron-rich heterocycles such as 1-methylindole using a variety of dispersed carbonate materials . The small amounts of benzothiophene-3-carboxylate observed with DMC and OMC-0 may arise from reactivity with residual MgO and SiO 2 from the synthesis procedures.…”

Section: Resultsmentioning

confidence: 98%

Improving Carbonate-Promoted C–H Carboxylation Using Mesoporous Carbon Supports

Chant

Kanan

2023

ACS Sustainable Chem. Eng.

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C–H carboxylation is an attractive way to utilize CO2 for chemical production provided that it does not consume resource-intensive reagents. Alkali carbonates dispersed into the pores of mesoporous supports display strongly basic reactivity under CO2, allowing them to be used as base promoters for C–H carboxylation of (hetero)arenes in the absence of other reagents or catalysts. Mesoporous oxides are convenient support materials, but only a relatively small fraction of the dispersed carbonate (ca. 10–20%) is converted to carboxylate products when metal oxide supports are used. Here, we compare mesoporous oxide and carbon supports and investigate the dependence of carbonate reactivity on the pore structure. We show that using mesoporous carbon supports can increase the carbonate conversion by 2–4× when compared to oxide supports. This improved carbonate reactivity is maintained across a variety of mesoporous carbons with different pore structures (ordered vs disordered) and pore diameters, indicating that the dispersed carbonate is intrinsically more reactive on the surface of a carbon material compared to an oxide surface. Reaction of the carboxylate products with dimethyl carbonate yields isolable methyl esters as the final product and regenerates the dispersed carbonate. We show that mesoporous carbon supports are robust to at least five cycles of successive C–H carboxylation and methylation. Understanding how the support structure affects dispersed carbonate reactivity is valuable for advancing C–H carboxylation toward practical application and utilizing these materials in other CO2 transformations.

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Section: Resultsmentioning

confidence: 98%

Improving Carbonate-Promoted C–H Carboxylation Using Mesoporous Carbon Supports

Chant

Kanan

2023

ACS Sustainable Chem. Eng.

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“…The Kanan group developed a strategy for C−H carboxylation of indoles using alkali carbonates dispersed in mesoporous TiO 2 in the presence of CO 2 (Scheme 19). [36] This method utilizes mild alkali carbonates, such as Na 2 CO 3 , K 2 CO 3 or Cs 2 CO 3 to accomplish C−H carboxylation by an electrophilic substitution mechanism. The base/TiO 2 support can be regenerated by heating under vacuum, resulting in a closed cycle for CO 2 utilization.…”

Section: Functionalization At the C3 Positionmentioning

confidence: 99%

“… C3−H selective carboxylation of indoles with M 2 CO 3 /TiO 2 materials by Kanan [36] …”

Section: Functionalization At the C3 Positionmentioning

confidence: 99%

Recent Advances in Metal‐Catalyzed Functionalization of Indoles

et al. 2021

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Indole is one of the most important heterocycles in organic synthesis, natural products, and drug discovery. Recently, tremendous advances in the selective functionalization of indoles have been reported. Although the most important advances have been powered by transition metal catalysis, exceedingly useful methods in the absence of transition metals have also been reported. In this review, we provide an overview of functionalization reactions of indoles that have been published in the last years with a focus on the most recent advances, aims, and future trends. The review is organized by the positional selectivity and type of methods used for functionalization. In particular, we discuss major advances in transition‐metal‐catalyzed C−H functionalization at the classical C2/C3 positions, transition‐metal‐catalyzed C−H functionalization at the remote C4/C7 positions, transition‐metal‐catalyzed cross‐coupling, and transition‐metal‐free functionalization.

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“…Interestingly, effective reactions such as phosgene gas with alcohol or phenol and epoxide with CO 2 molecules under the condition of zinc halides also furnish plenty of opportunities and choices for easy access to desirable carbonates on a large scale. 47,48 However, related research on the CO 2 adsorption and separation properties in carbonate-based HCPs, to the best of our knowledge, has been rarely reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

Carbonate-based hyper-cross-linked polymers with pendant versatile electron-withdrawing functional groups for CO₂adsorption and separation

Hou¹,

Hu²,

Liang³

et al. 2022

J. Mater. Chem. A

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Carbonate-promoted C–H carboxylation of electron-rich heteroarenes

Abstract: Carboxylation of heteroarenes with CO2 is achieved using alkali carbonate dispersed in mesoporous titania as a regenerable reagent.

Cited by 16 publications

References 44 publications

Improving Carbonate-Promoted C–H Carboxylation Using Mesoporous Carbon Supports

Improving Carbonate-Promoted C–H Carboxylation Using Mesoporous Carbon Supports

Recent Advances in Metal‐Catalyzed Functionalization of Indoles

Carbonate-based hyper-cross-linked polymers with pendant versatile electron-withdrawing functional groups for CO₂adsorption and separation

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Carbonate-promoted C–H carboxylation of electron-rich heteroarenes

Abstract: Carboxylation of heteroarenes with CO2 is achieved using alkali carbonate dispersed in mesoporous titania as a regenerable reagent.

Cited by 16 publications

References 44 publications

Improving Carbonate-Promoted C–H Carboxylation Using Mesoporous Carbon Supports

Improving Carbonate-Promoted C–H Carboxylation Using Mesoporous Carbon Supports

Recent Advances in Metal‐Catalyzed Functionalization of Indoles

Carbonate-based hyper-cross-linked polymers with pendant versatile electron-withdrawing functional groups for CO2adsorption and separation

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Product

Resources

About

Carbonate-based hyper-cross-linked polymers with pendant versatile electron-withdrawing functional groups for CO₂adsorption and separation