Alkynylation of radicals: spotlight on the “Third Way” to transfer triple bonds

Vaillant, Franck Le; Waser, Jérôme

doi:10.1039/c9sc03033f

Cited by 88 publications

(74 citation statements)

References 142 publications

(107 reference statements)

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“…The CF 3 -radical released can then add to an alkene to sustain a chain reaction, 17,18,19 and accordingly, reagent 2a was successfully applied to the a-trifluoromethyl-b-alkynylation of alkenes (1,2-difunctionalization). 20,18 We were very pleased to find that the cascade worked as planned, and reaction optimization (see Supplemental Information for full screening) revealed that this sequence is best conducted by using a a 0 -azobisisobutyronitrile as an initiator (30 mol %) in ethyl acetate as the solvent at 85 C by using 2 equivalents of the alkynyl triflone reagent 2a. The desired product, boronic ester 3a, was isolated in 72% yield, and the 1,2-difunctionalization product 21 that could be formed by direct trapping of the b-trifluoromethyl alkyl radical with reagent 2a was not identified.…”

Section: Resultsmentioning

confidence: 99%

Radical 1,3-Difunctionalization of Allylboronic Esters with Concomitant 1,2-Boron Shift

Jana

Bhunia

Studer

2020

Chem

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Radical 1,3-trifluoromethylation/alkynylation of various allylboronic esters with concomitant 1,2-boron shift with alkynyl triflones is reported. These chain reactions proceed via CF 3-radical addition to the allylic double bond, and the adduct radical undergoes 1,2-boron migration to give a translocated C-radical that is trapped by the alkynyl triflone. As products, 1,2,3-trisubstituted alkanes with the trifluoromethyl group at position 1 and the alkynyl functionality at position 3 are formed. The valuable boron moiety is retained in the product and is rearranged to position 2. By using trifluoromethanesulfonyl azide as the radical trapping reagent, the cascade provides a 1-trifluoromethyl-3-azidyl-alk-2-ylboronic ester as the product and Michael acceptors as trapping reagents in combination with the Langlois reagent as the CF 3-radical precursor applying photoredox catalysis afford the corresponding 3-alkylated congeners in a three-component process. Further, the stereochemical course of the 1,2-boron migration and the trapping reaction are investigated.

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Section: Resultsmentioning

confidence: 99%

Radical 1,3-Difunctionalization of Allylboronic Esters with Concomitant 1,2-Boron Shift

Jana

Bhunia

Studer

2020

Chem

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“…Vinylation of Free Radical . As several other hypervalent iodine transfer reagents, [65,66] VBXs proved to be good electrophilic radical acceptors. With the recent advent of photoredox catalysis several groups have started to apply VBX reagents under such conditions.…”

Section: Vbxmentioning

confidence: 98%

Vinylbenziodoxol(on)es: Synthetic Methods and Applications

Declas

Pisella

Waser

2020

Helvetica Chimica Acta

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Cyclic hypervalent iodine reagents are now frequently used in synthetic organic chemistry, either as oxidants or group-transfer reagents. Vinylbenziodoxol(on)es (VBXs) bearing alkene substituents have been less investigated than the corresponding trifluoromethyl or alkynyl reagents. Nevertheless, since 2016 the development of new synthetic methods to access VBXs has awakened the interest of the synthetic community, leading to new transformations highlighting their unique reactivity as electrophilic alkene synthons. In this review, an overview of the synthesis and applications of VBX reagents will be presented. The review is organized according to the two main classes of VBX reagents reported so far-simple alkyl/aryl-substituted VBXs and heteroatom (S, O, N, X)-substituted VBXs-as they differ significantly from the point of view of synthetic access.

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“…[34][35][36][37][38][39][40] Therefore, hypervalent iodine compounds have found wide application as efficient oxidative reagents and ligand transfer reagents in many reactions. [41][42][43][44][45][46][47][48][49] In fact, numerous oxidative reactions, benzyne-mediated reactions, and new bondforming reactions, such as carbon-carbon, carbon-heteroatom, or hetero-heteroatom bonds, have been accomplished using hypervalent iodine reagents under metal-free conditions. In particular, these reagents have been used for various ring construction reactions.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Oxazoline and Oxazole Derivatives by Hypervalent-Iodine-Mediated Oxidative Cycloaddition Reactions

et al. 2020

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Organohypervalent iodine reagents are widely used for the preparation of various oxazolines, oxazoles, isoxazolines, and isoxazoles. In the formation of these heterocyclic compounds, hypervalent iodine species can serve as the activating reagents for various substrates, as well as the heteroatom donor reagents. In recent research, both chemical and electrochemical approaches toward generation of hypervalent iodine species have been utilized. The in situ generated active species can react with appropriate substrates to give the corresponding heterocyclic products. In this short review, we summarize the hypervalent-iodine-mediated preparation of oxazolines, oxazoles, isoxazolines, and isoxazoles starting from various substrates.1 Introduction2 Synthesis of Oxazolines3 Synthesis of Oxazoles4 Synthesis of Isoxazolines5 Synthesis of Isoxazoles6 Conclusion

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Alkynylation of radicals: spotlight on the “Third Way” to transfer triple bonds

Abstract: This review explores the alkynylation of radicals as approach for the flexible and efficient synthesis of alkynes.

Cited by 88 publications

References 142 publications

Radical 1,3-Difunctionalization of Allylboronic Esters with Concomitant 1,2-Boron Shift

Radical 1,3-Difunctionalization of Allylboronic Esters with Concomitant 1,2-Boron Shift

Vinylbenziodoxol(on)es: Synthetic Methods and Applications

Synthesis of Oxazoline and Oxazole Derivatives by Hypervalent-Iodine-Mediated Oxidative Cycloaddition Reactions

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