Synthesis of quaternary centres by single electron reduction and alkylation of alkylsulfones

Nambo, Masakazu; Tahara, Yasuyo; Yim, Jacky C.‐H.; Yokogawa, Daisuke; Crudden, Cathleen M.

doi:10.1039/d1sc00133g

Cited by 36 publications

(21 citation statements)

References 60 publications

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“… 3 The photogeneration of these radicals has been only sparsely reported using Barton esters, 32 N -(acyloxy)phthalimides, 33 alkyl N -phthalimidoyl oxalates, 34 and alkyl carboxylates. 5b Thermal generation of these intermediates involved electrophiles such as alkyl halides 35 or alkylsulfones, 36 despite that in some cases, the desired C(sp 3 )–C(sp 3 ) bond formation failed to occur. 37 …”

Section: Resultsmentioning

confidence: 99%

Alkyl Radical Generation via C–C Bond Cleavage in 2-Substituted Oxazolidines

et al. 2022

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There is an urgent need to develop uncharged radical precursors to be activated under mild photocatalyzed conditions. 2-Substituted-1,3-oxazolidines ( E ox < 1.3 V vs SCE, smoothly prepared from the corresponding aldehydes) have been herein employed for the successful release of tertiary, α-oxy, and α-amido radicals under photo-organo redox catalysis. The reaction relies on the unprecedented C–C cleavage occurring from the radical cation of these heterocyclic derivatives. Such a protocol is applied to the visible-light-driven conjugate radical addition onto Michael acceptors and vinyl (hetero)arenes under mild metal-free conditions.

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Section: Resultsmentioning

confidence: 99%

Alkyl Radical Generation via C–C Bond Cleavage in 2-Substituted Oxazolidines

et al. 2022

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“…Building on Baran’s report, Nambo and Crudden reported an approach for the generation of reactive tertiary radicals through single-electron reduction of alkylsulfones 87 - 1 promoted by Zn and 1,10-phenanthroline (Scheme A) . The formed intermediates underwent Giese reaction with electron-withdrawing alkenes to form new quaternary carbon centers upon radical addition and hydrogenation.…”

Section: Radical-mediated Desulfonylation Of Sulfones Via C–s Bond Cl...mentioning

confidence: 99%

“…As expected, the formation of ring-opening product 86-3k from cyclopropylmethyl sulfone, 5-exo-trig cyclized product 86-3l from linear alkenyl sulfone, and racemic product from an enantioenriched sulfone 86-3m was observed, suggesting that a single-electron radical cross-coupling pathway Building on Baran's report, Nambo and Crudden reported an approach for the generation of reactive tertiary radicals through single-electron reduction of alkylsulfones 87-1 promoted by Zn and 1,10-phenanthroline (Scheme 87A). 304 The formed intermediates underwent Giese reaction 305 the present method was demonstrated through intramolecular cyclization of sulfones possessing olefin moieties to give a variety of spiro structures (Scheme 87B). Desulfonylative borylation of benzyl sulfones 88-1 with bis(pinacolato) diboron (B 2 pin 2 ) was revealed by Crudden, Nambo, and co-workers in 2019 (Scheme 88A).…”

Section: Radical-mediated Desulfonylation Of (Fluoro)alkylmentioning

confidence: 99%

Desulfonylation via Radical Process: Recent Developments in Organic Synthesis

et al. 2021

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As the "chemical chameleon", sulfonyl-containing compounds and their variants have been merged with various types of reactions for the efficient construction of diverse molecular architectures by taking advantage of their incredible reactive flexibility. Currently, their involvement in radical transformations, in which the sulfonyl group typically acts as a leaving group via selective C−S, N−S, O−S, S−S, and Se−S bond cleavage/ functionalization, has facilitated new bond formation strategies which are complementary to classical two-electron cross-couplings via organometallic or ionic intermediates. Considering the great influence and synthetic potential of these novel avenues, we summarize recent advances in this rapidly expanding area by discussing the reaction designs, substrate scopes, mechanistic studies, and their limitations, outlining the state-of-the-art processes involved in radical-mediated desulfonylation and related transformations. With a specific emphasis on their synthetic applications, we believe this review will be useful for medicinal and synthetic organic chemists who are interested in radical chemistry and radical-mediated desulfonylation in particular. CONTENTS

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“…7 Very recently, Crudden and her group members were able to generate quaternary centers by reducing alkylsulfones using Zn and 1,10-phenanthroline to generate tertiary radicals. 8 Recent developments in photoredox chemistry have enabled Hu 9 a and others 9 b – d to develop strategies involving radical fluoroalkylation. And the Gouverneur and Davis group used a photocatalytic radical modification of proteins.…”

mentioning

confidence: 99%

“…Inspection of the literature also provided evidence for this type of fragmentation. 8 Note, however, that generation of an alkyl sulfonyl radical cannot be ruled out. In fact, Wu et al and Ley et al reported the addition of alkyl sulfonyl radical to electron-deficient olefins.…”

mentioning

confidence: 99%