Hydrofunctionalization of Alkenes by Hydrogen‐Atom Transfer

Shenvi, Ryan A.; Matos, Jeishla L. M.; Green, Samantha A.

doi:10.1002/0471264180.or100.07

Cited by 21 publications

(19 citation statements)

References 135 publications

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“…The transition-metal-catalyzed hydrogen atom transfer (TM-HAT) of alkenes has recently attracted significant attention in synthetic organic chemistry . Originally, Halpern proposed the transfer of a hydrogen atom from a cobalt hydride species for the hydrogenation of anthracene .…”

Section: Introductionmentioning

confidence: 99%

Catalyst- and Silane-Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

et al. 2020

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The catalytic enantioselective synthesis of tetrahydrofurans, which are found in the structures of many biologically active natural products, via a transition-metal-catalyzed hydrogen atom transfer (TM-HAT) and radical-polar crossover (RPC) mechanism is described herein. Hydroalkoxylation of nonconjugated alkenes proceeded efficiently with excellent enantioselectivity (up to 94% ee) using a suitable chiral cobalt catalyst, N-fluoro-2,4,6-collidinium tetrafluoroborate, and diethylsilane. Surprisingly, the absolute configuration of the product was highly dependent on the steric hindrance of the silane. Slow addition of the silane, the dioxygen effect on the solvent, thermal dependence, and DFT calculation results supported the unprecedented scenario of two competing selective mechanisms. For the less-hindered diethylsilane, a high concentration of diffused carbon-centered radicals invoked diastereoenrichment of an alkylcobalt(III) intermediate by a radical chain reaction, which eventually determined the absolute configuration of the product. On the other hand, a more hindered silane resulted in less opportunity for a radical chain reaction, instead facilitating enantioselective kinetic resolution during the late-stage nucleophilic displacement of the alkylcobalt(IV) intermediate.

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Section: Introductionmentioning

confidence: 99%

Catalyst- and Silane-Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

et al. 2020

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“… We also used topological strategies in planning, which identified the opportunity to disconnect the topologically strategic C8–C9 bond of 4 breaking a bridged six-membered ringto substantially simplify the overall synthetic route. We speculated that it may be possible to address construction of the bridgehead C8 all-carbon quaternary stereocenter by employing hydrogen atom transfer (HAT)-initiated intramolecular radical conjugate addition, using alkene 5 . Alternatively, keto amine 4 might also be generated from 5 via a stepwise strategy, perhaps using acid- or base-promoted intramolecular cyclization followed by a hydrogenation.…”

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confidence: 99%

Total Synthesis of (−)-Daphnezomines A and B

et al. 2020

J. Am. Chem. Soc.

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Daphnezomines A and B are structurally unusual Daphniphyllum alkaloids that contain a unique aza-adamantane core skeleton. Herein, a modular approach to these alkaloids is presented that exploits a diverse array of reaction strategies. Commencing from a chiral pool terpene–(S)-carvone, the azabicyclo[3.3.1]nonane backbone, which occurs widely in Daphniphyllum alkaloids, was easily accessed through a Sharpless allylic amination and a palladium-catalyzed oxidative cyclization. A protecting group enabled a stereoselective B-alkyl Suzuki–Miyaura coupling sequence and an Fe-mediated hydrogen atom transfer (HAT)-based radical cyclization were then applied to construct C6 and C8 stereocenters. A final epimer locking strategy enabled the assembly of the highly congested aza-adamantane core, thereby achieving the first total synthesis of (−)-daphnezomines A and B in 14 steps.

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“…An emerging strategy in asymmetric hydrofunctionalization chemistry capitalizes on transition-metal hydrides (M–H) that react with alkenes via hydrogen atom transfer (HAT). − The ensuing formation of a solvent-caged metallo/organic radical pair offers a versatile platform for functionalization with a variety of coupling partners (Scheme ). Such catalytic systems are common with first-row transition metals, including Fe, Co, and Mn, and proceed under mild reaction conditions with high levels of chemoselectivity.…”

Section: Metal-hydride Hydrogen Atom Transfermentioning

confidence: 99%

Catalytic Asymmetric Hydroalkoxylation of C–C Multiple Bonds

et al. 2021

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Asymmetric hydroalkoxylation of alkenes constitutes a redox-neutral and 100% atom-economical strategy toward enantioenriched oxygenated building blocks from readily available starting materials. Despite their great potential, catalytic enantioselective additions of alcohols across a C–C multiple bond are particularly underdeveloped, especially compared to other hydrofunctionalization methods such as hydroamination. However, driven by some recent innovations, e.g., asymmetric MHAT methods, asymmetric photocatalytic methods, and the development of extremely strong chiral Brønsted acids, there has been a gratifying surge of reports in this burgeoning field. The goal of this review is to survey the growing landscape of asymmetric hydroalkoxylation by highlighting exciting new advances, deconstructing mechanistic underpinnings, and drawing insight from related asymmetric hydroacyloxylation and hydration. A deep appreciation of the underlying principles informs an understanding of the various selectivity parameters and activation modes in the realm of asymmetric alkene hydrofunctionalization while simultaneously evoking the outstanding challenges to the field moving forward. Overall, we aim to lay a foundation for cross-fertilization among various catalytic fields and spur further innovation in asymmetric hydroalkoxylations of C–C multiple bonds.

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Hydrofunctionalization of Alkenes by Hydrogen‐Atom Transfer

Cited by 21 publications

References 135 publications

Catalyst- and Silane-Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

Catalyst- and Silane-Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

Total Synthesis of (−)-Daphnezomines A and B

Catalytic Asymmetric Hydroalkoxylation of C–C Multiple Bonds

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