Radical Addition to 1,4-Benzoquinones:  Addition at <i>O</i>- versus <i>C</i>-Atom

Kumli, Eveline; Montermini, Florian; Renaud, Philippe

doi:10.1021/ol0624629

Cited by 34 publications

(31 citation statements)

References 19 publications

(15 reference statements)

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“…Recently, we reported that alkyl radicals generated from Balkylcatecholboranes add onto 1,4-benzoquinone at either the C-atom leading to substituted hydroquinones or at the O-atom resulting in aryl ethers. [7] It was shown that competing O-addition strongly depends on the bulkiness of the alkyl radical. The new reaction procedure with in situ generated modified B-alkylcatecholboranes 12 afforded the 1,4-conjugate addition products 23 and aryl ethers 24 in ratios comparable to the original method but with increased isolated yields (Scheme 5).…”

Section: Resultsmentioning

confidence: 99%

“…[7] In the current procedure with 12, this excess amount could be reduced to 1.1 equiv. without observing the formation of 2-alkylated quinones.…”

Section: Resultsmentioning

confidence: 99%

“…[5] This reaction represents a modified and improved version of the Brown-Negishi reaction. [6] More recently, this reaction was extended to the addition of radicals onto benzoquinones, [7] thus creating straightforward access to 2-substituted hydroquinones, which are common subunits in biologically active secondary metabolites (Scheme 1). BAlkylcatecholborane-mediated radical reactions produce, lowed by treatment with the dihydroxytetrahydroisoquinoline.…”

Section: Introductionmentioning

confidence: 99%

“…In such cases, a large discrepancy between yields estimated by GC or NMR analysis of the crude products and isolated yields is observed as shown in the example depicted in Scheme 1. [7] Scheme 1. Radical addition to 1,4-benzoquinone.…”

Section: Introductionmentioning

confidence: 99%

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ModifiedB‐Alkylcatecholboranes as Radical Precursors

2010

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Generation of radicals from B-alkylcatecholboranes represents an efficient tin-free procedure for the generation of alkyl radicals. A modified version of this method has been developed. The simple catechol is replaced by a dihydroxylated tetrahydroisoquinoline, which can be separated from the reaction products by simple extraction with an aqueous acid solution. The modified alkyl radical precursors are easily prepared from alkenes by hydroboration with BH 3 ·Me 2 S fol-

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Section: Resultsmentioning

confidence: 99%

“…[7] In the current procedure with 12, this excess amount could be reduced to 1.1 equiv. without observing the formation of 2-alkylated quinones.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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ModifiedB‐Alkylcatecholboranes as Radical Precursors

2010

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“…[7,8] The formation of a C À Se bond from organoboranes is limited to selenocyanates. [9] Recently, we discovered that B-alkylcatecholboranes are extremely useful radical precursors that can participate in efficient carboncarbon [7,[10][11][12] and carbon-oxygen [12,13] bond formation. [14] Chain reactions involving arenesulfonyl radicals and B-alkylcatecholboranes are particularly efficient as demonstrated by the allylation reaction with allylic sulfones.…”

Section: Introductionmentioning

confidence: 99%

An Efficient Radical Procedure for the Halogenation and Chalcogenation of B‐Alkylcatecholboranes

et al. 2008

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An efficient formal anti-Markovnikov addition of HX (X = Cl, Br, I, SR and SeR) to olefins under mild reaction conditions is described. The procedure is based on the hydroboration of alkenes with catecholborane. The conversion of the intermediate B-alkylcatecholboranes to the corresponding halides, sulfides and selenides is based on a common process, i.e., generation of a radical from the alkylborane followed by abstraction of a heteroatom from an aromatic sulfonyl reagent. The efficiency of these radical reactions is remarkable. The mildness of the reaction conditions is well illustrated by the preparation of iodoalkanes. Despite the notorious reactivity of iodoalkanes under radical reaction conditions, no product degradation was observed.

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Boron‐Mediated Radical Reactions

André‐Joyaux¹,

Gnägi²,

Gnägi‐Lux³

et al. 2022

Patai's Chemistry of Functional Groups

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This chapter focuses on the use of boron‐containing reagents in radical reactions. In all reactions presented here, boron is playing a key role in the radical process either by being part of the radical process or by influencing the reactivity of the radical and nonradical species. The diversity of radical chemistry involving organoboron species is spectacular. They represent a unique source of radicals for chain reactions allowing for instance efficient radical initiation at low temperature and generation of a broad range of functionalized alkyl radicals from easily prepared organoboranes. Recent developments in redox chemistry including photoredox catalysis, electrochemistry, and single‐electron‐transfer processes have allowed the generation of alkyl and aryl radicals from stable organoboron derivatives such as alkyl‐ and aryl‐trifluoroborates. A broad range of synthetic applications such as radical cascade processes, multicomponent reactions, and cross‐coupling reactions in the presence of suitable metals are possible. Besides radical generation, boron‐containing radical precursors and radical traps are becoming of increasing importance to prepare building blocks enclosing a boron moiety suitable for further functionalization. Merging radical processes with classical boron chemistry including Suzuki–Miyaura‐type cross‐coupling processes; homologation via 1,2‐metallate rearrangement; and conversions to alcohols, amines, and related compounds offers unique opportunities for applications in organic synthesis.

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Radical Addition to 1,4-Benzoquinones: Addition at O- versus C-Atom

Cited by 34 publications

References 19 publications

ModifiedB‐Alkylcatecholboranes as Radical Precursors

ModifiedB‐Alkylcatecholboranes as Radical Precursors

An Efficient Radical Procedure for the Halogenation and Chalcogenation of B‐Alkylcatecholboranes

Boron‐Mediated Radical Reactions

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