Silver-Catalyzed Radical Transformation of Aliphatic Carboxylic Acids to Oxime Ethers

Zhu, Yuchao; Wen, Xiaojin; Song, Song; Jiao, Ning

doi:10.1021/acscatal.6b02074

Cited by 51 publications

(23 citation statements)

References 135 publications

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“…In recent years, the well-designed sulfonyl oxime ether reagents showed great reactivity in alkyl radical chemistry 42 – 46 . Inspired by the recently developed silver-catalyzed radical reactions 47 – 60 and our continues interest in developing radical reactions with sulfonyl reagents 58 , 59 , we envisioned that the sequence silver-catalyzed radical process would achieve the challenging C–H bond functionalization. To investigate our hypothesis, we initially chose A as the radical acceptor for the direct functionalization of the widely existed 1-octanol ( 1a ).…”

Section: Resultsmentioning

confidence: 99%

Silver-catalyzed remote Csp3-H functionalization of aliphatic alcohols

et al. 2018

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Aliphatic alcohols are common and bulk chemicals in organic synthesis. The site-selective functionalization of non-activated aliphatic alcohols is attractive but challenging. Herein, we report a silver-catalyzed δ-selective Csp3-H bond functionalization of abundant and inexpensive aliphatic alcohols. Valuable oximonitrile substituted alcohols are easily obtained by using well-designed sulphonyl reagents under simple and mild conditions. This protocol realizes the challenging δ-selective C–C bond formation of simple alkanols.

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Section: Resultsmentioning

confidence: 99%

Silver-catalyzed remote Csp3-H functionalization of aliphatic alcohols

et al. 2018

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“…We had hypothesized that DMSO can selectively form the hydrogen bonding with the hydroxyl. To prove this, we studied the reaction between 3,3‐diphenylpropan‐1‐ol 12 and a radical acceptor 8 , which afforded phenyl migration product 13 in 18 % yield via silver catalyzed O−H homolysis process [15g, 20] . Interestingly, the yield of 13 increased with the addition of DMSO, and then decreased when DMSO was added too much.…”

Section: Methodsmentioning

confidence: 99%

DMSO‐Enabled Selective Radical O−H Activation of 1,3(4)‐Diols

et al. 2020

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Control of selectivity is one of the central topics in organic chemistry. Although unprecedented alkoxyl-radicalinduced transformations have drawn a lot of attention, compared to selective CÀH activation, selective radical OÀH activation remains less explored. Herein, we report a novel selective radical O À H activation strategy of diols by combining spatial effects with proton-coupled electron transfer (PCET). It was found that DMSO is an essential reagent that enables the regioselective transformation of diols. Mechanistic studies indicated the existence of the alkoxyl radical and the selective interaction between DMSO and hydroxyl groups. Moreover, the distal C À C cleavage was realized by this selective alkoxylradical-initiation protocol. The selective transformation of hydroxyl (OH) groups in diand polyols is a frequently encountered problem in organic synthesis, in contexts ranging from simple alcohol transformations to the preparation of highly functionalized natural products. [1] Despite the importance of this issue, strategies for the selective O À H activation are rare compared to the fastgrowing studies on selective CÀH activation. [2] The classic methods for selective activation of one hydroxyl in diols involve ionic transformations by steric regulation or based on special hydrocarbon structure. [3] Unlike traditional ionic alcohol transformations involving nucleophilic substitution/ addition, [4] oxidation [5] and elimination [6] of hydroxyls, the alkoxyl radical induced transformations have drawn more attention with the discovery of unprecedented strategies for the generation of alkoxy radicals from alcohol without the need for pre-activation. [7] The OÀH radical processes greatly enlarged the reaction types of alcohols either with alkoxyl radical induced b scission [8] or hydrogen abstraction. [9, 10] However, to the best of our knowledge, the general methods for the alkoxyl radical induced distal CÀC cleavage remains unexplored (Scheme 1 a). Moreover, the realized OÀH radical transformations are limited to the activation of mono-ols, so far, there is a lack of selective radical O À H activation due to the almost identical bond-dissociation energy between two hydroxyls in diols (% 105 kcal mol À1) [11] (Scheme 1 b). To address this problem, we paid our attention to the strategy of proton coupled electron transfer (PCET), which was reported that a Brønsted base and an oxidant can synergistically remove a proton and an electron from the substrate to afford a free radical (Scheme 1 c). [12] Recently, Knowles and co-workers significantly achieved the O À H bond homolysis through PCET. [13] Inspired by these reports, we hypothesized that if we could find a proper Brønsted or Lewis base that can selectively form a hydrogen bond with one hydroxyl in diols, we would have a chance to selectively activate one O À H bond and realize the selective alkoxyl radical transformation of diols (Scheme 1 d). Scheme 1. Selective hydroxyl activation of diols.

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“…Notably, the leaving sulfonyl radicals can be utilized providing β-sulfonyl carbonyl compounds which is without precedence in the chemistry of these well-developed sulfone-based radical trap reagents. 11,12 …”

Section: Introductionmentioning

confidence: 99%