XF Bai

A novel Si-based Lewis superacid was synthesized by using highly electron-withdrawing perfluoropinacolato substituents. The formed silane was obtained as the acetonitrile mono-adduct and comprehensively characterized. The reaction with Et₃SiF led to fluoride abstraction yielding the anionic fluorosilicate and the acetonitrile stabilized silylium ion. Catalysis screenings demonstrated high activity in Lewis acid catalyzed reactions.

Abstract

Despite the earth abundance and easy availability of silicon, only few examples of isolable neutral silicon centered Lewis superacids are precedent in the literature. To approach the general drawbacks of limited solubility and unselective deactivation pathways, we introduce a Lewis superacid, based on perfluorinated pinacol substituents. The compound is easily synthesized on a gram-scale as the corresponding acetonitrile mono-adduct 1⋅(MeCN) and was fully characterized, including single crystal X-ray diffraction analysis (SC-XRD) and state-of-the-art computations. Lewis acidity investigations by the Gutmann-Beckett method and fluoride abstraction experiments indicate a Lewis superacidic nature. The challenging Si−F bond activation of Et₃SiF is realized and promising catalytic properties are demonstrated, consolidating the potential applicability of silicon centered Lewis acids in synthetic catalysis.

Nature, Published online: 17 February 2021; doi:10.1038/s41586-020-03149-9

Polycarbonates and polyesters with materials properties like those of high-density polyethylene can be recycled chemically by depolymerization to their constituent monomers, re-polymerization yielding material with uncompromised processing and materials properties.

Nature Chemistry, Published online: 16 September 2021; doi:10.1038/s41557-021-00767-2

Triphenylphosphonium ylides (Wittig reagents) that selectively react with sulfenic acids—a pivotal post-translational cysteine modification in redox biology—are developed. This bioconjugation method enables a site-specific proteome-wide stoichiometry analysis of S-sulfenylation, and visualization of redox-dependent changes in mitochondrial cysteine oxidation and the redox-triggered generation of triphenylphosphonium for the controlled delivery of small molecules to mitochondria.

A Ni-catalyzed direct decarbonylative borylation of aryl carboxylic acids with B₂cat₂ has been established. B₂cat₂ serves as a borylating agent, but also activates the carboxylic acid substrate towards decarbonylative coupling, playing a dual role in this reaction. A combination of experimental and computational studies reveals that the reaction proceeds through a hitherto unknown concerted decarbonylation and reductive elimination step.

Abstract

The Ni-catalyzed decarbonylative borylation of (hetero)aryl carboxylic acids with B₂cat₂ has been achieved without recourse to any additives. This Ni-catalyzed method exhibits a broad substrate scope covering poorly reactive non-ortho-substituted (hetero)aryl carboxylic acids, and tolerates diverse functional groups including some of the groups active to Ni⁰ catalysts. The key to achieve this decarbonylative borylation reaction is the choice of B₂cat₂ as a coupling partner that not only acts as a borylating reagent, but also chemoselectively activates aryl carboxylic acids towards oxidative addition of their C(acyl)−O bond to Ni⁰ catalyst via the formation of acyloxyboron compounds. A combination of experimental and computational studies reveals a detailed plausible mechanism for this reaction system, which involves a hitherto unknown concerted decarbonylation and reductive elimination step that generates the aryl boronic ester product. This mode of boron-promoted carboxylic acid activation is also applicable to other types of reactions.

Nature Catalysis, Published online: 20 October 2021; doi:10.1038/s41929-021-00688-w

Enantioselective C(sp3)–C(sp3) coupling plays an important role in organic synthesis, but limitations remain. Now, cobalt-catalysed enantioselective C(sp3)–C(sp3) coupling between achiral fluoroalkenes and alkyl halides enables the streamlined and auxiliary-free synthesis of chiral fluoroalkanes.

A simple nickel catalyst converts terminal alkynes and formic acid to α-chiral carboxylic acids in high enantioselectivity. The reaction proceeds via the hydrocarboxylation of alkynes and enantioselective transfer hydrogenation of acrylic acids.

Abstract

We report a stereoselective conversion of terminal alkynes to α-chiral carboxylic acids using a nickel-catalyzed domino hydrocarboxylation-transfer hydrogenation reaction. A simple nickel/BenzP* catalyst displayed high activity in both steps of regioselective hydrocarboxylation of alkynes and subsequent asymmetric transfer hydrogenation. The reaction was successfully applied in enantioselective preparation of three nonsteroidal anti-inflammatory profens (>90 % ees) and the chiral fragment of AZD2716.

The facile synthesis of C-aryl nucleoside analogues from readily available furanose acetates and aryl iodides is disclosed. This nickel-catalyzed cross-electrophile coupling showed good functional-group compatibility and excellent β-selectivity. The high chemoselectivity with respect to aryl iodides enabled the efficient preparation of a variety of C-aryl halide furanosides suitable for various post-functionalization reactions.

Abstract

Canonical nucleosides are vulnerable to enzymatic and chemical degradation, yet their stable mimics—C-aryl nucleosides—have demonstrated potential utility in medicinal chemistry, chemical biology, and synthetic biology, although current synthetic methods remain limited in terms of scope and selectivity. Herein, we report a cross-electrophile coupling to prepare C-aryl nucleoside analogues from readily available furanosyl acetates and aryl iodides. This nickel-catalyzed modular approach is characterized by mild reaction conditions, broad substrate scope, excellent β-selectivity, and high functional-group compatibility. The exclusive chemoselectivity with respect to the aryl iodide enables efficient preparation of a variety of C-aryl halide furanosides suitable for various downstream transformations. The practicality of this transformation is demonstrated through the synthesis of a potent analogue of a naturally occurring NF-κB activator.

Nature Chemistry, Published online: 23 September 2021; doi:10.1038/s41557-021-00783-2

The valorization of lignin is generally implemented through the cleavage of labile C–O bonds to produce aromatic monomers in up to 40 wt% yield. The remaining material consists of lignin dimers and oligomers connected by C–C bonds, but now a method has been developed for the oxidative cleavage of these C–C bonds using oxoammonium salts, to produce benzoquinones.

Nature Chemistry, Published online: 07 October 2021; doi:10.1038/s41557-021-00790-3

Diazoolefins tend to be highly reactive compounds, and thus experimental evidence of these species is currently limited. Now, the reactivity and coordination chemistry of N-heterocyclic diazoolefins has been described. Diazoolefins are observed to form in reactions of N-heterocyclic olefins with nitrous oxide. The products benefit from resonance stabilization, enabling isolation on a preparative scale and comprehensive characterization.

Nature Chemistry, Published online: 24 May 2021; doi:10.1038/s41557-021-00698-y

Many C–C bond activation methods involve strain-releasing cleavage of small rings to compensate for unfavourable kinetics and thermodynamics. Now, the 1,2-positional interchange of vicinal C–C and C–Pd bonds has been reported, giving access to quaternary carbon–palladium bonds. This dyotropic rearrangement has been used for the enantioselective synthesis of functionalized fluorinated cyclopentanes.

Nature Chemistry, Published online: 27 May 2021; doi:10.1038/s41557-021-00706-1

Current methods for the synthesis of prostaglandins suffer from low yields and lengthy steps. Now, a strategy for their enantioselective synthesis has been developed with rhodium-catalysed enyne cycloisomerization as the key step. This concise route was scaled up, enabling the preparation of fluprostenol on a 20-gram scale.