Tin‐Free Radical Allylation of <i>B</i>‐Alkylcatecholboranes

Schaffner, Arnaud‐Pierre; Renaud, Philippe

doi:10.1002/anie.200351171

Cited by 74 publications

(42 citation statements)

References 40 publications

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“…[34] By using phenyl sulfones, the fragmentation produces a stable phenylsulfonyl radical that should react with B-alkylcatecholborane to sustain the chain reaction (Scheme 18). Oxygen-centered radicals react efficiently with B-alkylcatecholboranes.…”

Section: Radical Allylationmentioning

confidence: 99%

B‐Alkylcatecholborane‐Mediated Radical Reactions

Schaffner

Renaud

2004

Eur J Org Chem

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B‐Alkylcatecholboranes, easily prepared by hydroboration of alkenes, represent a very efficient source of primary, secondary and tertiary alkyl radicals. The very high sensitivity towards oxygen‐and heteroatom‐centered radicals makes them particularly attractive for the development of radical chain processes. Very mild conditions for radical hydroxylation of organoboranes using either TEMPO (= 2,2,6,6‐tetramethylpiperidine‐N‐oxyl) or oxygen have been developed. Conjugate addition of β‐alkylcatecholboranes to enones and enals proceeds very efficiently under oxygen intiation. Inter‐ and intramolecular addition to other radical traps such as α,β‐unsaturated esters, amides and sulfones requires the use of PTOC‐OMe {1‐[(methoxycarbonyl)oxy]pyridine‐2(1H)‐thione} as a chain transfer reagent. Finally, a very general method for the radical hydroallylation of olefins using allyl sulfones as radical traps is presented. This reaction takes advantage of the very efficient reaction of B‐alkylcatecholboranes with the benzenesulfonyl radical. The diversity of the chemistry presented in this microreview demontrates that catecholborane represents a very good alternative to tin derivatives for radical reactions involving alkyl radicals. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Section: Radical Allylationmentioning

confidence: 99%

B‐Alkylcatecholborane‐Mediated Radical Reactions

Schaffner

Renaud

2004

Eur J Org Chem

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“…181,182,184 Hydroboration of (þ)-a-pinene 241 with catecholborane occurs with the anticipated regio-and stereoselectivity to give the alkylborane 242 (Scheme 67). In situ reaction with an allyl sulfone and a radical initiator (di-tert-butyl hyponitrite) then gave the allylated product 243.…”

Section: Intermolecular Addition Reactionsmentioning

confidence: 98%

Radicals in organic synthesis. Part 1

Rowlands

2009

Tetrahedron

201

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“…Precipitation from MeOH/H 2 Og ave the enantiomerically pure product in 15 %y ield from 7. To further illustrate the potential of this approach, hydroallylation, [31] hydrosulfanylation, [32] and hydrobromination [32] reactions of cyclohexene and cyclopentene 1a and 1g were examined by using 2-(ethoxycarbonyl)prop-2-enyl phenyl sulfone, Sphenyl benzenesulfonothioate,and benzenesulfonyl bromide as radical traps (Scheme 6). [30] Theh ydroazidation presented above represents only one of the possible one-pot processes combining an enantioselective hydroboration with ar adical reaction.…”

Section: Scheme 4 Enantioselective Hydroazidationo Ftrisubstituted Amentioning

confidence: 99%

Enantioselective Hydroazidation of Trisubstituted Non‐Activated Alkenes

Meyer

Renaud

2017

Angew Chem Int Ed

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A one-pot procedure for the enantioselective hydroazidation of non-activated trisubstituted alkenes is described. Hydroboration with monoisopinocampheylborane (IpcBH ) provides dialkylboranes that are in situ selectively converted into monoalkyl-substituted catecholboranes; these undergo radical azidation upon treatment with benzenesulfonyl azide and a radical initiator. Enantiomerically enriched azides were thus obtained in yields of 59-81 % and enantioselectivities of up to 94:6 e.r. (98:2 e.r. if the intermediate dialkylborane is purified by crystallization). A rapid access to enantiomerically pure (+)-rodocaine is also described. The use of other arenesulfonyl radical traps enables enantioselective hydroallylation, hydrosulfanylation, and hydrobromination reactions with yields of 71-86 %.

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Tin‐Free Radical Allylation of B‐Alkylcatecholboranes

Cited by 74 publications

References 40 publications

B‐Alkylcatecholborane‐Mediated Radical Reactions

B‐Alkylcatecholborane‐Mediated Radical Reactions

Radicals in organic synthesis. Part 1

Enantioselective Hydroazidation of Trisubstituted Non‐Activated Alkenes

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