A SN1 mechanistic approach to the Williamson ether reaction via photoredox catalysis applied to benzylic C(sp3)–H bonds

Fitzpatrick, Nicholas A.; Zamani, Leila; Das, Mrinmoy; Yayla, Hatice G.; Lall, Manjinder S.; Zhang, Patricia

doi:10.1016/j.tet.2022.132986

Cited by 13 publications

(10 citation statements)

References 32 publications

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“…The influence of steric hindrance was subsequently examined. Surprisingly, good yields were obtained for both hydrogen sulfates in the reactions with secondary alcohols ( 20 , 21 , 23 , 24 ), superior to conventional etherification method as reported previously [11] . However, tertiary alcohols as substrates are not able to achieve the desired transesterification yields due to the difficulty of weakly nucleophilic reagents with enhanced steric resistances to initiate transesterification reaction [26] and the generation of a large number of symmetric amine ethers as by‐products detected by GC–MS ( 22 , 25 ).…”

Section: Resultssupporting

confidence: 63%

“…Surprisingly, good yields were obtained for both hydrogen sulfates in the reactions with secondary alcohols (20,21,23,24), superior to conventional etherification method as reported previously. [11] However, tertiary alcohols as substrates are not able to achieve the desired transesterification yields due to the difficulty of weakly nucleophilic reagents with enhanced steric resistances to initiate transesterification reaction [26] and the generation of a large number of symmetric amine ethers as byproducts detected by GC-MS (22,25). Further, in the reaction of the hydrogen sulfates with diols, monoesterification was preferred with high selectivity instead of diesterication (26,27,6,29,30,32); notably, the hydroxyl group with lower steric hindrance was more reactive (28,31).…”

Section: Resultsmentioning

confidence: 99%

“…[9] However, these methods are deficient in the synthesis of asymmetric amine ethers for reasons of poor selectivity, incompatibility, inertness of the system, etc. Recently, the cutting-edge means like catalysis with ionic liquid, [10] photocatalysis, [11] electrocatalysis, [12] copolymerized cotton fabric catalysis, [13] promotion with supercritical carbon dioxide, [14] have been employed to prepare ethers. However, they also suffer from high cost and harsh reaction conditions.…”

Section: Introductionmentioning

confidence: 99%

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General Construction of Asymmetric Amine Ethers via Efficient Transesterification

Li,

Hong,

Qian

et al. 2023

Chemistry A European J

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A novel method to prepare asymmetric amine ethers is reported. Tertiary amine alcohol hydrogen sulfate intermediates are prepared through a reactive distillation process, followed by the transesterification process to afford eventually asymmetric amine ethers. Experiments and DFT calculations revealed the essential roles the sulfate group plays in the highly selective monoesterification process. This clean method is tolerant towards various functional groups with good yields under mild condition, which is obviously superior compared to the conventional processes.

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Section: Resultssupporting

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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General Construction of Asymmetric Amine Ethers via Efficient Transesterification

Li,

Hong,

Qian

et al. 2023

Chemistry A European J

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“…The Supporting Information is available free of charge at the Supporting experimental data: experimental procedures, characterization data, and copies of the 1 H and 13 NMR spectra (PDF). Additional references cited within the Supporting Information [41–59] …”

Section: Supporting Informationmentioning

confidence: 99%

Lewis Base‐Boryl Radicals Promoted Selective Mono‐ and Di‐ Hydrodechlorination of Trichloroacetamides and Acetates

Bo,

Phang,

Zhao

et al. 2024

Eur J Org Chem

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Mono and dichloro‐substituted organic molecules are shown to possess significant roles in various fields, especially in medicinal chemistry. One approach to synthesizing these compounds involves the selective dechlorination of easily prepared trichloromethyl compounds. Nevertheless, developing a practical approach that allows selective mono‐ and dihydrodechlorination is a challenging task. Herein, we introduced a method for selective mono‐ and dihydrodechlorination of trichloroacetamides and acetates which was promoted by two different Lewis base‐boryl radicals. Accordingly, 4‐dimethylaminopyridine (DMAP)‐borane enabled mono‐substitution of chlorine atom by hydrogen while dihydro‐substitution of chlorine atoms was promoted by N‐heterocyclic carbene (NHC)‐boryl radical. Using deuterated Lewis base‐borane as deuterium atom source, mono‐ and dideuterodechlorination were also successfully took place. This protocol features broad substrate scope and operates under mild reaction conditions.

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“…While all three methods proceed via a carbocation intermediate, noticeably lacking in the scope of each protocol is the formation of fully substituted centers arising from in situ -generated tertiary carbocations. Recently, our group, concurrently with the Doyle group, published a visible-light photoredox-catalyzed [HAT+RPC] mechanism that can engage classically weak nucleophiles, including fluoride, and readily forge fully substituted centers from tertiary C–H precursors. We hypothesized that the established platform could be extended to the formation of an array of N -benzyl azoles, including those bearing fully substituted centers.…”

mentioning

confidence: 99%

Azolation of Benzylic C–H Bonds via Photoredox-Catalyzed Carbocation Generation

et al. 2023

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A visible-light photoredox-catalyzed method is reported that enables the coupling between benzylic C−H substrates and N−H azoles. Classically, medicinally relevant N-benzyl azoles are produced via harsh substitution conditions between the azole and a benzyl electrophile in the presence of strong bases at high temperatures. Use of C−H bonds as the alkylating partner streamlines the preparation of these important motifs. In this work, we report the use of N-alkoxypyridinium salts as a critically enabling reagent for the development of a general C(sp 3 )−H azolation. The platform enables the alkylation of electron-deficient, -neutral, and -rich azoles with a range of C−H bonds, most notably secondary and tertiary partners. Moreover, the protocol is mild enough to tolerate benzyl electrophiles, thus offering an orthogonal approach to existing S N 2 and cross-coupling methods.

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A SN1 mechanistic approach to the Williamson ether reaction via photoredox catalysis applied to benzylic C(sp3)–H bonds

Cited by 13 publications

References 32 publications

General Construction of Asymmetric Amine Ethers via Efficient Transesterification

General Construction of Asymmetric Amine Ethers via Efficient Transesterification

Lewis Base‐Boryl Radicals Promoted Selective Mono‐ and Di‐ Hydrodechlorination of Trichloroacetamides and Acetates

Azolation of Benzylic C–H Bonds via Photoredox-Catalyzed Carbocation Generation

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