Oxidative Cross-Coupling of Two Different Phenols: An Efficient Route to Unsymmetrical Biphenols

More, Nagnath Yadav; Jeganmohan, Masilamani

doi:10.1021/acs.orglett.5b01324

Cited by 88 publications

(43 citation statements)

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“…[18] Waldvogel and co-workers reported an [b] 19 %AcOOH (1 equiv electrochemical oxidative cross-coupling reaction of phenols. [20] More recently,t he iron-catalyzed oxidative cross-coupling reaction of two different phenols was achieved by the group of Pappo, [21] in which the cross-coupling selectivities of two different phenols are nicely controlled. [20] More recently,t he iron-catalyzed oxidative cross-coupling reaction of two different phenols was achieved by the group of Pappo, [21] in which the cross-coupling selectivities of two different phenols are nicely controlled.…”

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Organo‐Iodine(III)‐Catalyzed Oxidative Phenol–Arene and Phenol–Phenol Cross‐Coupling Reaction

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“…Similarly, 1e reacted with 1c,thus affording the cross-coupling product 4ce in moderate yield. [20] In another example,the group of Pappo reported the oxidative coupling of 1a with various phenols (1e, 1f, 1h, and 1k)in4 0-96 %yields. Tr eatment of the disubstituted 4methyl phenol (1k)with 1a gave the coupling product 4ak in 46 %y ield.…”

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Organo‐Iodine(III)‐Catalyzed Oxidative Phenol–Arene and Phenol–Phenol Cross‐Coupling Reaction

et al. 2016

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“…[8,9] Classically, nonsymmetric 2,2'-biphenols are prepared via transition-metal-catalyzed coupling reactions. [11][12][13][14][15] This approach has been addressed by a variety of efficient protocols. The leaving-group chemistry along with complex and costly catalysts (e.g.…”

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Selective Synthesis of Partially Protected Nonsymmetric Biphenols by Reagent‐ and Metal‐Free Anodic Cross‐Coupling Reaction

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The oxidative cross-coupling of aromatic substrates without the necessity of leaving groups or catalysts is described. The selective formation of partially protected nonsymmetric 2,2'-biphenols via electroorganic synthesis was accomplished with a high yield of isolated product. Since electric current is employed as the terminal oxidant, the reaction is reagent-free; no reagent waste is generated as only electrons are involved. The reaction is conducted in an undivided cell, and is suitable for scale-up and inherently safe. The implementation of O-silyl-protected phenols in this transformation results in both significantly enhanced yields and higher selectivity for the desired nonsymmetric 2,2'-biphenols. The use of a bulky silyl group to block one hydroxyl moiety makes the final product less prone to oxidation. Furthermore, the partially silyl-protected 2,2'-biphenols are versatile building blocks that usually require tedious or low-yielding synthetic pathways. Additionally, this strategy facilitates a large variety of new substrate combinations for oxidative cross-coupling reactions.

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“…Theg roup of Jeganmohan tried the oxidative cross-coupling for the synthesis the biphenols 4ag and 4ah, thus giving the products in 48 %a nd 56 %y ields,r espectively. [20] In another example,the group of Pappo reported the oxidative coupling of 1a with various phenols (1e, 1f, 1h, and 1k)in4 0-96 %yields. [21] Aplausible catalytic cycle for the present iodine-catalyzed oxidative coupling of phenols is illustrated in Scheme 3.…”

Section: Methodsmentioning

confidence: 99%

“…[19] Jeganmohan and co-workers also described an oxidative cross-coupling of two different phenols using K 2 S 2 O 8 and Bu 4 N + HSO 3 À (10 mol %) in CF 3 COOH. [20] More recently,t he iron-catalyzed oxidative cross-coupling reaction of two different phenols was achieved by the group of Pappo, [21] in which the cross-coupling selectivities of two different phenols are nicely controlled.…”

Section: Methodsmentioning

confidence: 99%

Organo‐Iodine(III)‐Catalyzed Oxidative Phenol–Arene and Phenol–Phenol Cross‐Coupling Reaction

et al. 2016

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The direct oxidative coupling reaction has been an attractive tool for environmentally benign chemistry.Reported herein is that the hypervalent iodine catalyzed oxidative metalfree cross-coupling reaction of phenols can be achieved using Oxone as at erminal oxidant in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP). This method features ah igh efficiency and regioselectivity,a sw ell as functional-group tolerance under very mild reaction conditions without using metal catalysts.The biaryl unit including phenol is an important structural motif for aw ide range of functional molecules such as bioactive natural products,l iquid crystals,a nd ligands for transition-metal catalysts.[1] Thec ommon approaches to the syntheses of these structures involve cross-couplings between aryl halides and organometallic reagents.[2] In these cases of multistep syntheses,s uch as Suzuki or Stille coupling,t he phenol moiety usually has to be protected. Recently,t ransition-metal-catalyzed direct functionalization of the CÀH bonds on aromatic compounds,involving the activation of the aromatic C À Hbond, has attracted much attention in terms of synthetic efficiencya nd minimization of atomic waste. [3,4] In contrast, the oxidative cross-coupling of unprotected phenols has received considerable attention because of the atom-economical and environmentally friendly processes. [5] Although various kinds of homocoupling reactions of unprotected phenols involving the use of Fe,C u, Mn, and Ti salts have been developed, [6] thecatalytic oxidative cross-coupling reaction of phenols by CÀH/CÀH' coupling has remained challenging. [7] This reaction is ac hallenge because,w hen simple phenols are employed in oxidative cross-couplings,the desired products are often concomitantly formed along with homocoupling by-products.M oreover,t he formation of higher-molecular-weight polymers or C,O-connected phenol portions,for example,quinol ethers,might also occur depending on the oxidant and the reaction conditions.[2b] Am ajor reason for this side reaction is the difficulty associated with the tunable reactivity of phenols by controlling their oxidation potential using aprotecting group for the phenol hydroxy group.T herefore,t he development of an efficient catalytic cross-coupling of unprotected phenols for the construction of biaryl compounds is still highly desirable.R ecently,W aldvogel and co-workers reported an electrochemical phenolarene cross-coupling reaction using boron-doped diamond electrodes.[8] Very recently,the iron-catalyzed oxidative crosscoupling reaction of phenols with arenes was successfully achieved.[9] While recent metal-catalyzed cross-couplings of phenols have been studied, the organocatalytic cross-coupling reaction still remains particularly challenging.R ecently,w e developed the oxidative cross-coupling reaction of aromatic compounds using hypervalent iodine reagents. [10][11][12][13][14][15] Inspired by these studies,wenow report abroadly applicable organoiodine(III)-catalyzed oxidative cross-coupling reaction of pheno...

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Oxidative Cross-Coupling of Two Different Phenols: An Efficient Route to Unsymmetrical Biphenols

Cited by 88 publications

References 46 publications

Organo‐Iodine(III)‐Catalyzed Oxidative Phenol–Arene and Phenol–Phenol Cross‐Coupling Reaction

Organo‐Iodine(III)‐Catalyzed Oxidative Phenol–Arene and Phenol–Phenol Cross‐Coupling Reaction

Selective Synthesis of Partially Protected Nonsymmetric Biphenols by Reagent‐ and Metal‐Free Anodic Cross‐Coupling Reaction

Organo‐Iodine(III)‐Catalyzed Oxidative Phenol–Arene and Phenol–Phenol Cross‐Coupling Reaction

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