Mild and Highly Efficient Copper(I) Inspired Acylation of Alcohols and Polyols

Mensah, Enoch A.; Earl, Lindsey

doi:10.3390/catal7010033

Cited by 8 publications

(6 citation statements)

References 40 publications

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“…The residue was purified by silica gel column chromatography (eluent: n -hexane:EtOAc = 6:1 to 4:1) to give 2b as a colorless oil (0.80 g, 90% yield). Spectral data for 2b were consistent with those reported in ref .…”

Section: Methodssupporting

confidence: 88%

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

2023

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We describe an efficient method for benzylic C−H fluorination via sequential hydrogen-atom transfer (HAT) and oxidative radical-polar crossover utilizing the Ag(I)/Selectfluor system. Amide ligands, such as benzamide and sulfonamide, substantially facilitate the processes leading to a carbocation intermediate, which subsequently reacts with nucleophilic fluorinating reagent to form a C−F bond. This protocol is applicable to the fluorination of all 1°, 2°, and 3°C−H bonds as well as to late-stage C−H fluorination of bioactive molecules.T he introduction of a C−F bond into organic molecules alters their physical, chemical, and biological properties, and consequently, fluorine-containing compounds are of interest in many research fields. 1 However, few fluorinecontaining compounds are found in nature, 2 and therefore, artificial construction of the C−F bond is required. Tremendous effort has been devoted to the development of C−F bond-forming reactions 3 by many research groups including ours, 4 but there is still a need for methods to form C−F bonds under mild conditions, which would be suitable for late-stage modification.An oxidation system using Ag(I) and Selectfluor (1) is one of the most powerful tools for the construction of the C−F bond under very mild conditions. 5 In this system, Ag(I) is considered to be oxidized by 1 to produce high-valent silver species, such as Ag(II) or Ag(III), acting as a strong singleelectron oxidant. The oxidation of Ag(I) is operationally simple, occurring even at room temperature, and various radical fluorinations using the Ag(I)/Selectfluor system have been developed (Scheme 1A). For example, Li and co-workers reported efficient methods for decarboxylative fluorination 5a and deboronofluorination. 5c These reactions begin with singleelectron transfer (SET) between high-valent silver species and appropriate functional groups to afford an alkyl radical, followed by fluorine-atom transfer (FAT) from 1 to give the corresponding product. Although these methods can form the C−F bond in a site-specific fashion, preinstallation of certain functional groups in the starting material is required. Given that most biologically active compounds possess an abundance of C(sp 3 )−H bonds, direct and regioselective C(sp 3 )−H fluorination would be an attractive option for rapid fluoro derivatization. In this context, Baxter and co-workers developed benzylic C−H fluorination with the Ag(I)/ Selectfluor system, 5f,h in which the diazabicyclo radical cation 1′ generated from 1 is considered to serve as a hydrogen-atom transfer (HAT) reagent. Then, FAT from 1 to the resulting alkyl radical leads to the fluorinated product (Scheme 1B). However, this reaction is not applicable to 3°C−H

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Section: Methodssupporting

confidence: 88%

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

2023

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“…The results of the optimization are summarized in Table , which clearly shows that the optimal condition for the acetylation was the reaction of aniline (1 mmol) with acetic anhydride (1.2 mmol) in the presence of WTMC (1 mmol) and two drops of H 3 PO 4 on heating for 10 min, which gave 98% yield of acetanilide. Although H 3 PO 4 was used as the catalyst in the synthesis of aspirin from salicylic acid by using acetic anhydride, and the acylation of phenol and amine with copper(I) and nickel(II) in the presence of imidazole is mild at room temperature, no systematic studies have been done for the acetylation of phenols and anilines.…”

Section: Resultsmentioning

confidence: 99%

“…The reaction condition was optimized by conducting the acetylation of aniline with acetic anhydride in the presence of various quantities of WTMC. The results of the optimization are summarized in Table 2, which clearly shows that the optimal condition for the acetylation was the reaction of SCHEME 1 Acetylation of phenols and anilines mediated by transitionmetal complexes PO 4 was used as the catalyst in the synthesis of aspirin from salicylic acid by using acetic anhydride, [49] and the acylation of phenol and amine with copper(I) and nickel(II) in the presence of imidazole is mild at room temperature, [50,51] no systematic studies have been done for the acetylation of phenols and anilines.…”

Section: Introductionmentioning

confidence: 99%

Werner transition‐metal complex (WTMC)‐mediated mild and efficient chemo‐selective acylation of phenols and anilines under solvent‐free condition

Sarief

Haque

Feroze

et al. 2018

J Chinese Chemical Soc

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Werner‐type transition‐metal complexes (WTMC) such as [Co(NH3)5Cl]Cl2, Cu[(NH3)4]SO4, Mn(acac)3, Ni[(NH3)6]Cl2, Ni[(en)3]S2O3, and Hg[Co(SCN)4] efficiently promote the chemoselective acetylation of phenols and anilines under solvent‐free condition. The results of this study clearly shows that the optimal condition for the acetylation of anilines/phenols (1 mmol) (2a–r) with acetic anhydride (1.2 mmol) in the presence of WTMC (1 mmol) and two drops of H3PO4 on heating for 10 min under solvent‐free condition gives the corresponding acetanilides/phenyl acetate (3a–r) in good to excellent yield. Furthermore, the method is simple, efficient, chemoselective, and eco‐friendly under solvent‐free condition for the acetylation of anilines and phenols promoted by WTMC by using acetic anhydrate as the acetylating agent. The simple preparation of the catalyst, easy procedure of the acetylation reaction, and simple work‐up indicate the importance of WTMC for such reactions.

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“…In general, several reagents have been used as catalysts for esterification from organic compounds such as DMAP [7], DBU [8], p-TSA [9], alkoxide [10], to transition metal complexes of titanium [11], copper [12], iron [13], and zinc [14,15]. Another approach to this catalytic esterification is using biocatalyst such as enzymes to achieve asymmetric ester products [16].…”

Section: Introductionmentioning

confidence: 99%

Catalyst Free Hydroxyl Protection of Quinine via Esterification

Roswanda

Putra

Mardiastuti

et al. 2019

KEM

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A method to protect the hydroxyl group of quinine via esterification is developed. The method uses acetyl and benzoyl as the protection group. The method employs no catalyst that generates reasonable yield at 83% for acetyl and 73% for benzoyl. This catalyst free method emphasizes on the importance substrate reactivity to achieve free catalyst procedure. Ester form of quinine synthesized might be further functionalized for various aims in accordance to its rich functional group and building block of quinine.

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Mild and Highly Efficient Copper(I) Inspired Acylation of Alcohols and Polyols

Cited by 8 publications

References 40 publications

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

Amide-Ligand-Promoted Silver-Catalyzed C–H Fluorination via Radical/Polar Crossover

Werner transition‐metal complex (WTMC)‐mediated mild and efficient chemo‐selective acylation of phenols and anilines under solvent‐free condition

Catalyst Free Hydroxyl Protection of Quinine via Esterification

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