Reductive radical-polar crossover: traditional electrophiles in modern radical reactions

Pitzer, Lena; Schwarz, J. Luca; Glorius, Frank

doi:10.1039/c9sc03359a

Cited by 227 publications

(130 citation statements)

References 41 publications

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“…Then, the generated [ArBr] •− radical anion undergoes fragmentation to release a bromide anion and an aryl radical II 56,57 , which undergoes facile intramolecular radical addition to the C2-C3 double bond of indole to afford the benzylic radical III. The following SET with 4CzIPN •− delivers the carbon anion intermediate IV 58,59 , which could undergo nucleophilic addition to CO 2 [60][61][62][63] . Following protonation provides the dearomative arylcarboxylation product 2.…”

Section: Resultsmentioning

confidence: 99%

Reductive dearomative arylcarboxylation of indoles with CO2 via visible-light photoredox catalysis

et al. 2020

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Catalytic reductive coupling of two electrophiles and one unsaturated bond represents an economic and efficient way to construct complex skeletons, which is dominated by transitionmetal catalysis via two electron transfer. Herein, we report a strategy of visible-light photoredox-catalyzed successive single electron transfer, realizing dearomative arylcarboxylation of indoles with CO 2. This strategy avoids common side reactions in transition-metal catalysis, including ipso-carboxylation of aryl halides and β-hydride elimination. This visible-light photoredox catalysis shows high chemoselectivity, low loading of photocatalyst, mild reaction conditions (room temperature, 1 atm) and good functional group tolerance, providing great potential for the synthesis of valuable but difficultly accessible indoline-3-carboxylic acids. Mechanistic studies indicate that the benzylic radicals and anions might be generated as the key intermediates, thus providing a direction for reductive couplings with other electrophiles, including D 2 O and aldehyde.

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Section: Resultsmentioning

confidence: 99%

Reductive dearomative arylcarboxylation of indoles with CO2 via visible-light photoredox catalysis

et al. 2020

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“…In contrast to the above reductive generation of iodomethyl radical, the general access of halomethyl radical was realized via oxidative SET process with halosilicate as the methylene source (Scheme b) , . Of note, these cyclopropanation reactions based on photooxidative generation of halomethyl radical proceed efficiently via redox‐neutral radical‐polar crossover without any aid of external additives. Due to the superior leaving group ability of iodide over bromide and chloride, the use of high reactive iodomethyl radical has more opportunities to prevent the formation of the undesired noncyclized Giese‐type addition product .…”

Section: Figurementioning

confidence: 99%

Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical‐Polar Crossover Cyclopropanation of Alkenes

et al. 2020

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A general protocol for visible‐light‐induced cyclopropanation of alkenes was developed with bromomethyl silicate as a methylene transfer reagent, offering a robust tool for accessing highly valuable cyclopropanes. In addition to α‐aryl or methyl‐substituted Michael acceptors and styrene derivatives, the unactivated 1,1‐dialkyl ethylenes were also shown to be viable substrates. Apart from realizing the cyclopropanation of terminal alkenes, the methyl transfer reaction has been further demonstrated to be amenable to the internal olefins. The photocatalytic cyclopropanation of 1,3‐bis(1‐arylethenyl)benzenes was also achieved, giving polycyclopropane derivatives in excellent yields. With late‐stage cyclopropanation as the key strategy, the synthetic utility of this transformation was also demonstrated by the total synthesis of LG100268.

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“…[60][61][62][63][64][65][66] Moreover, owing to the generally mild reaction conditions and often high functional group tolerance, radical chemistry represents a well-suited strategy for chemoselective modifications of peptides and proteins. [61][62][63][64][65][66] In general, radical approach [67][68][69][70][71][72] is widely applied in the field of organic synthesis for the rapid construction of complex molecular architectures [73][74][75] and the total synthesis of natural products under safe and mild conditions. [76][77][78][79][80][81] Even in nature many of oxidation processes catalyzed by heme proteins and metalloporphyrins have proceeded through a radical mechanism.…”

Section: Introductionmentioning

confidence: 99%

Advances in Asymmetric Amino Acid Synthesis Enabled by Radical Chemistry

2020

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Chiral amino acids (AAs), being the main "building" blocks of the living organisms, are also an important class of organic compounds which broadly applied in synthetic chemistry, biochemistry, catalysis and the designing of new drugs. According to the industrial-commodity market, chiral non-proteinogenic AAs containing various functional groups come to the fore. To date, radical cross-coupling reactions are becoming an option as an attractive powerful tool for AA syntheses. Owing to mild reaction conditions and high functional-group tolerance, radical chemistry represents an ideal strategy for the synthesis of challenging complex non-proteinogenic AAs. Moreover, the radical cross-coupling allows introducing AA residue into drug scaffolds and natural compounds. In the present review, we wish to summarize and discuss all the reported to date methods of the asymmetric synthesis of AAs using radical chemistry by presenting a comprehensive account of the literature in this field going back to 1990. We especially emphasize on a radical chemistry approach and, exclusively, on stereoselective synthesis of various α-, β-, γ-AAs and derivatives employing a different type of radical initiators starting from AIBN and organostannes and ending with powerful photoredox catalysis. Furthermore, the mechanism of the reported reactions will be discussed. Radicals Generated from AA Derivatives in Conjugate Additions 6.1. Radicals Generated from α-Substituted Glycine Derivatives in AA Synthesis 6.2. Modification of Chiral AA Side Chain by Radical Chemistry 7.

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Reductive radical-polar crossover: traditional electrophiles in modern radical reactions

Abstract: The concept of reductive radical-polar crossover (RRPCO) reactions has recently emerged as a valuable and powerful tool to overcome limitations of both radical and traditional polar chemistry.

Cited by 227 publications

References 41 publications

Reductive dearomative arylcarboxylation of indoles with CO2 via visible-light photoredox catalysis

Reductive dearomative arylcarboxylation of indoles with CO2 via visible-light photoredox catalysis

Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical‐Polar Crossover Cyclopropanation of Alkenes

Advances in Asymmetric Amino Acid Synthesis Enabled by Radical Chemistry

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