LongLarf

Na-exchanged X type zeolite, commercially available as MS-13X, effectively catalyzes thiol-disulfane exchange reactions under aerobic mild conditions to give the unsymmetrical disulfanes in good-to-high yields. Various thiols and disulfanes are tolerant in the catalytic systems. Preliminary mechanistic studies suggest the involvement of base-catalyzed S_N2-S displacement and/or addition-elimination mechanisms assisted by H-bonding interactions.

Abstract

Convenient catalytic synthetic methods for the preparation of unsymmetrical disulfanes are described. Na-exchanged X type zeolite (Na-X), commercially available as MS-13X, effectively catalyzes thiol-disulfane exchange reactions with 1.0 equivalent of thiols and 2.5–3.0 equivalents of disulfanes at 10 °C to room temperature under air. The reactions of sterically-hindered disulfanes or electron-deficient thiol substrates require high temperatures under inert atmospheres to maintain the good product yields. Various functionalized thiols and disulfanes are tolerant in the present catalytic systems, affording the corresponding unsymmetrical disulfanes in good-to-high yields (up to 96 %). The Na-X catalyst was successfully recycled 10 times without loss of yield. Preliminary mechanistic studies suggest the involvement of base-catalyzed S_N2-S displacement and/or addition-elimination mechanisms, assisted by hydrogen-bonding interactions.

Nature Catalysis, Published online: 21 September 2021; doi:10.1038/s41929-021-00675-1

Methods for the direct one-step replacement of a hydrogen atom in a C–H bond by an organic functional group can create enormous possibilities for synthetic applications. On the way to solve this challenge, the discovery of the reaction of organopalladium complexes with olefins opened a new era in catalysis and organic chemistry.

Publication date: 22 October 2021

Source: Tetrahedron, Volume 99

Author(s): Keying Ding

Synthesis
DOI: 10.1055/a-1643-8526

Reported here is an efficient enantioselective transfer hydrogenation of cyclic oxocarbenium ions generated in situ through collapse of the corresponding acetal substrates. The asymmetric approach provides straightforward access to a variety of chiral α-aryl substituted 1,3-dihydroisobenzofurans in high yields with excellent enantioselectivities. α-Alkynyl substituted 1,3-dihydroisobenzofurans were also proved to be suitable substrates. In addition, when the reaction was performed at gram scale, the desired product was obtained in good yields with excellent enantioselectivity.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
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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.

Publication date: 1 December 2021

Source: Ecotoxicology and Environmental Safety, Volume 225

Author(s): Marisa A. Wirth, Lars Longwitz, Marion Kanwischer, Peter Gros, Peter Leinweber, Thomas Werner

Green and versatile! The photocatalytic C(sp²)−H azolation of arenes using heterogeneous carbon nitride is reported. This strategy exhibits a broad substrate scope and is amenable to the late-stage functionalization of several pharmaceuticals. The catalyst can be easily recovered and reused leading to greener and more sustainable routes.

Abstract

The functionalization of aryl C(sp²)−H bonds is a useful strategy for the late-stage modification of biologically active molecules, especially for the regioselective introduction of azole heterocycles to prepare medicinally-relevant compounds. Herein, we describe a practical photocatalytic transformation using a mesoporous carbon nitride (mpg-CN _x ) photocatalyst, which enables the efficient azolation of various arenes through direct oxidation. The method exhibits a broad substrate scope and is amenable to the late-stage functionalization of several pharmaceuticals. Due to the heterogeneous nature and high photocatalytic stability of mpg-CN _x , the catalyst can be easily recovered and reused leading to greener and more sustainable routes, using either batch or flow processing, to prepare these important compounds of interest in pharmaceutical and agrochemical research.

Directed evolution of P411 heme enzymes enables intermolecular C−H amidation with high yields and exquisite enantioselectivity. The biocatalytic process utilizes stable hydroxamate esters as nitrenoid precursors and is amenable to scaleup. Mechanistic studies reveal rate-determining nitrenoid formation followed by a stepwise, hydrogen atom transfer-mediated C−H functionalization.

Abstract

Directed evolution of heme proteins has opened access to new-to-nature enzymatic activity that can be harnessed to tackle synthetic challenges. Among these, reactions resulting from active site iron-nitrenoid intermediates present a powerful strategy to forge C−N bonds with high site- and stereoselectivity. Here we report a biocatalytic, intermolecular benzylic C−H amidation reaction operating at mild and scalable conditions. With hydroxamate esters as nitrene precursors, feedstock aromatic compounds can be converted to chiral amides with excellent enantioselectivity (up to >99 % ee) and high yields (up to 87 %). Kinetic and computational analysis of the enzymatic reaction reveals rate-determining nitrenoid formation followed by stepwise hydrogen atom transfer-mediated C−H functionalization.

Nature, Published online: 15 September 2021; doi:10.1038/d41586-021-02479-6

The departing German chancellor’s support for science and rigour in policymaking has proved transformative — except on climate change.

This Minireview provides an overview of methods employing DAST to obtain valuable building blocks and compounds having pharmacological features. Fluorination of β-amino alcohols, proceeding through opening of an aziridinium ion, leading to rearranged products was described in detail. In addition, the intramolecular cyclization induced by DAST resulting in unprecedent heterocyclic compounds was presented. The description of neighboring group participation and debenzylative cycloetherification in the synthesis of sugars derivatives will probably be of interest to scientists dealing with carbohydrate chemistry.

Abstract

Nucleophilic fluorination is one of the fundamental reactions in organic chemistry, as well as a convenient tool for the synthesis of fluorinated building blocks with a potential biological activity. In this minireview, diethylaminosulfur trifluoride (DAST) mediated reactions leading to valuable building blocks and bioactive compounds will be discussed. We focused on results that have been published since 2010. Transformation of β-amino alcohols, heterocyclic frameworks synthesis, as well as rearrangement reactions have been described in detail.