Use of Lewis Acids in Free Radical Reactions

Renaud, Philippe; Gerster, Michèle

doi:10.1002/(sici)1521-3773(19981016)37:19<2562::aid-anie2562>3.0.co;2-d

Cited by 264 publications

(14 citation statements)

References 55 publications

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“…Enantiopure sulfoxides have been widely used as chiral auxiliaries in a broad range of synthetic reactions like carbon-carbon 1,2 and carbon-oxygen 3 bond-forming reactions, cycloaddition reactions, [4][5][6] radical addition reactions 7,8 and in asymmetric catalysis. 9 Enantiopure sulfoxides have also found use in the pharmaceutical industry due to their important biological activity, for example, gastric acid proton pump inhibitor like Esomeprazole.…”

Section: Introductionmentioning

confidence: 99%

Catalytic asymmetric oxidation of sulfides to sulfoxides using (R)-6,6$$^{\prime }$$-Diphenyl-BINOL as a chiral ligand

et al. 2019

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The chiral metal complex produced in situ from (R)-6,6-Diphenyl-BINOL and Ti(O−i−Pr) 4 as a catalytic system for asymmetric sulfoxidation of aryl methyl and aryl benzyl sulfides in the presence of 70% aqueous TBHP as the oxidant has been investigated. The influence of variation of reagents mole ratios, temperature, solvent and oxidant was examined, and the optimized conditions were then used to oxidize a number of aryl methyl and aryl benzyl sulfides, producing sulfoxides in high enantiopurities (up to 90% ee) and good yields (up to 81%).

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Section: Introductionmentioning

confidence: 99%

Catalytic asymmetric oxidation of sulfides to sulfoxides using (R)-6,6$$^{\prime }$$-Diphenyl-BINOL as a chiral ligand

et al. 2019

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“…The results were encouraging since, beside an 80% isolated yield, there was a >99% ee (being ZnCl 2 the best solution). The use of a combination of low temperatures and Lewis acid for stereoselective radical cyclization is known [ 118 , 119 , 120 , 121 , 122 , 123 ], however, in this case, the use of zinc chloride proved to be far more better than other LA (such as MgBr 2 or Yb(OTf) 3 ), probably owing to the presence of the polymer-embedded sugar which creates a favorable environment for zinc-mediated stereoselection.…”

Section: Exploitation Of Radical Chemistry In Sp Synthesismentioning

confidence: 99%

From Polymer to Small Organic Molecules: A Tight Relationship between Radical Chemistry and Solid-Phase Organic Synthesis

Mirizzi

Pulici

2011

Molecules

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Since Gomberg’s discovery of radicals as chemical entities, the interest around them has increased through the years. Nowadays, radical chemistry is used in the synthesis of 75% of all polymers, inevitably establishing a close relationship with Solid-Phase Organic Synthesis. More recently, the interest of organic chemists has shifted towards the application of usual “in-solution” radical chemistry to the solid-phase, ranging from the use of supported reagents for radical reactions, to the development of methodologies for the synthesis of small molecules or potential libraries. The aim of this review is to put in perspective radical chemistry, moving it away from its origin as a synthetic means for solid supports, to becoming a useful tool for the synthesis of small molecules.

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“…In conjunction with our studies 19 , 20 on the development of enantioselective, dual-catalysis photoredox reactions 38 – 41 , we speculated that radical coupling reactions 42 , 43 for connecting two distinct odd-electron partners using an extrinsic stereocontrol factor 44 – 46 would provide a complementary and structurally versatile approach for accessing the enantioconvergent products ( b ). This method would avoid the limitation of the narrow substrate scope faced by direct S H 2-based radical transformations 47 , where stereoselectivity is also underdeveloped. Notably, the precise and absolute stereocontrol in a reaction with such a low-energy barrier and rapid bond-forming process is a formidable challenge, especially when building an uncommon full-carbon quaternary stereocenter.…”

Section: Introductionmentioning

confidence: 99%

Formal enantioconvergent substitution of alkyl halides via catalytic asymmetric photoredox radical coupling

Li¹,

Kong²,

Qiao³

et al. 2018

Nat Commun

136

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Classic nucleophilic substitution reactions (SN1 and SN2) are not generally amenable to the enantioselective variants that use simple and racemic alkyl halide electrophiles. The merging of transition metal catalysis and radical chemistry with organometallic nucleophiles is a versatile method for addressing this limitation. Here, we report that visible light-driven catalytic asymmetric photoredox radical coupling can act as a complementary and generic strategy for the enantioconvergent formal substitution of alkyl haldies with readily available and bench-stable organic molecules. Single-electron reductive debrominations of racemic α-bromoketones generate achiral alkyl radicals that can participate in asymmetric Csp3–Csp3 bonds forming cross-coupling reactions with α-amino radicals derived from N-aryl amino acids. A wide range of valuable enantiomerically pure β2- and β2,2-amino ketones were obtained in satisfactory yields with good-to-excellent enantioselectivities by using chiral phosphoric acid catalysts to control the stereochemistry and chemoselectivity. Fluoro-hetero-quaternary and full-carbon quaternary stereocenters that are challenging to prepare were successfully constructed.

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Use of Lewis Acids in Free Radical Reactions

Cited by 264 publications

References 55 publications

Catalytic asymmetric oxidation of sulfides to sulfoxides using (R)-6,6$$^{\prime }$$-Diphenyl-BINOL as a chiral ligand

Catalytic asymmetric oxidation of sulfides to sulfoxides using (R)-6,6$$^{\prime }$$-Diphenyl-BINOL as a chiral ligand

From Polymer to Small Organic Molecules: A Tight Relationship between Radical Chemistry and Solid-Phase Organic Synthesis

Formal enantioconvergent substitution of alkyl halides via catalytic asymmetric photoredox radical coupling

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