Organoboranes as a Source of Radicals

and, Cyril Ollivier; Renaud, Philippe

doi:10.1021/cr010001p

Cited by 497 publications

(306 citation statements)

References 231 publications

(411 reference statements)

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“…Due to π bonding between boron and oxygen, boronic esters are less reactive than trialkylboranes toward alkoxyl radicals. Very interestingly, B-alkylcatecholboranes (= 2-alkylbenzo[d] [1,3,2]dioxaboroles) behave differently. They are extremely sensitive toward oxygen and react readily with alkoxyl radicals.…”

Section: Reactivity Of B-alkylcatecholboranesmentioning

confidence: 99%

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Boron: A key element in radical reactions

Renaud

Beauseigneur

Brecht‐Forster

et al. 2007

Pure and Applied Chemistry

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Boron derivatives are becoming key reagents in radical chemistry. Here, we describe reactions where an organoboron derivative is used as a radical initiator, a chain-transfer reagent, and a radical precursor. For instance, B-alkylcatecholboranes, easily prepared by hydroboration of alkenes, represent a very efficient source of primary, secondary, and tertiary alkyl radicals. Their very high sensitivity toward oxygen-and heteroatom-centered radicals makes them particularly attractive for the development of radical chain processes such as conjugate addition, allylation, alkenylation, and alkynylation. Boron derivatives have also been used to develop an attractive new procedure for the reduction of radicals with alcohols and water. The selected examples presented here demonstrate that boron-containing reagents can efficiently replace tin derivatives in a wide range of radical reactions.

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Section: Reactivity Of B-alkylcatecholboranesmentioning

confidence: 99%

“…The ability of organoboron compounds to participate in free radical reactions has been identified since the earliest investigation of their chemistry [1][2][3]. For instance, the autoxidation of organoboranes (Scheme 1) has been proven to involve radical intermediates [4,5].…”

Section: Introductionmentioning

confidence: 99%

Boron: A key element in radical reactions

Renaud

Beauseigneur

Brecht‐Forster

et al. 2007

Pure and Applied Chemistry

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“…The use of organoboranes as a source of radicals has been recently reviewed. 4 It has been extensively used in the development of tin-free radical chemistry, bypassing the tedious purification procedures often associated with the use of tin reagents. [5][6][7] It has also been used in solid-supported radical C-C bond formation.…”

Section: Methodsmentioning

confidence: 99%

Triethylborane (Et₃B)

O’Mahony¹

2004

Synlett

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This feature focuses on a reagent chosen by a postgraduate, highlighting the uses and preparation of the reagent in current research Triethylborane (Et 3 B) Gavin O'MahonyGavin O'Mahony was born in Donegal, Ireland in 1980 and began studying chemistry at Queen's University Belfast in 1997. After receiving his B.Sc. in 2000, he joined the research group of Dr Paul J. Stevenson at Queen's and is currently undertaking a Ph.D. project in conjunction with CSS Ltd. as part of the CAST Award Scheme. His research is in palladium and ruthenium catalysed approaches to pumiliotoxin alkaloids.

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“…The radical 7 underwent coupling with cyclopentenone 6a (5 eq), producing adduct 8a in 77% yield. The C-Se bond of 5a was inert upon treatment with Et 3 B (3 eq)/O 2 at 0°C, 58,59) and 5a was quantitatively recovered. In contrast, the C-Te bond of 5b was effectively cleaved using the above Et 3 B/O 2 system to generate bridgehead radical 7, which reacted with 6a (3 eq) at 0°C to afford 8a in 85% yield.…”

Section: Radical-mediated Three-component Reactionmentioning

confidence: 99%

Radical-Mediated Three-Component Reaction: A Study toward the Total Synthesis of Resiniferatoxin

Urabe

2015

CHEMICAL & PHARMACEUTICAL BULLETIN

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This review summarizes the efforts to develop a radical-mediated three-component reaction and its application to a convergent approach to synthesize the 5/7/6-tricyclic framework (ABC-rings) of the densely functionalized dephnane diterpene, resiniferatoxin. The α-alkoxy bridgehead radical species, which was designed as the radical donor of the three-component reaction, was generated from O,Se-and O,Te-acetals under two different conditions. The generated α-alkoxy bridgehead radical effectively underwent the threecomponent reaction with α,β-unsaturated ketones and allyltributyltin/aldehyde under each of the conditions, giving rise to a wide variety of multiply functionalized 2,3-trans disubstituted cyclopentenone moieties. One of the established reactions was utilized as the key assembling reaction of the ABC-tricyclic framework of resiniferatoxin. The reaction of the bridgehead radical of the highly functionalized 6-membered C-ring, the 5-membered A-ring, and an allyltributyltin derivative effectively produced the C4-branched AC-rings. The last B-ring was constructed from the coupling adduct in two steps through the 7-endo cyclization, delivering the tricyclic framework possessing the correct C8 and 9-stereocenters of resiniferatoxin. The present methods demonstrate the power of the three-component reaction using an α-alkoxy bridgehead radical in a convergent approach to the complex architectures of daphnane diterpenes.

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Organoboranes as a Source of Radicals

Cited by 497 publications

References 231 publications

Boron: A key element in radical reactions

Boron: A key element in radical reactions

Triethylborane (Et₃B)

Radical-Mediated Three-Component Reaction: A Study toward the Total Synthesis of Resiniferatoxin

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Organoboranes as a Source of Radicals

Cited by 497 publications

References 231 publications

Boron: A key element in radical reactions

Boron: A key element in radical reactions

Triethylborane (Et3B)

Radical-Mediated Three-Component Reaction: A Study toward the Total Synthesis of Resiniferatoxin

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Triethylborane (Et₃B)