MarjoW

Abstract

Amines are a very important class of compounds and the selective synthesis of differently substituted primary, secondary and tertiary alkyl amines is challenging. Here we present the synthesis of primary, secondary, and tertiary alkyl amines from ammonia and alcohols, aldehydes, ketones and hydrogen by combining borrowing hydrogen or hydrogen autotransfer and reductive amination with hydrogen. The key is a nanostructured, bimetallic Co/Sc catalyst able to mediate both reactions or concepts efficiently. We observe a broad product scope, a very good functional group tolerance, upscaling is easily accomplished and our catalyst is reusable.

Synlett
DOI: 10.1055/a-2102-7006

A decarboxylative oxidation of carboxylic acids was developed through visible-light-induced photocatalysis with molecular oxygen as a green oxidant and copper as a co-catalyst. This reaction worked smoothly on various type of acids, and could potentially be used in modifications of natural products. The high efficiency of this transformation was demonstrated on over 40 substrates.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Synlett
DOI: 10.1055/a-2097-1051

Electrochemical potentials of photocatalysts are solvent dependent. One of the largest discrepancies is observed when water is used in place of organic solvents as the reaction media. Unfortunately, the redox potentials for many photocatalysts in water have not been determined, at least under one unifying set of conditions, and this greatly hinders the rational design of sustainable and biocompatible photoredox reactions. Herein, we measure the spectral and electrochemical properties of the most common photoredox catalysts in water and catalog their absorption and fluorescence maxima and ground- and excited-state potentials.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Synthesis
DOI: 10.1055/a-2081-1830

The ubiquity of carboxylic acids as naturally derived or man-made chemical feedstocks has spurred the development of powerful, decarboxylative C–C bond-forming transformations for organic synthesis. Carboxylic acids benefit not only from extensive commercial availability, but are stable surrogates for organohalides or organometallic reagents in transition-metal-catalysed cross-coupling. Open shell reactivity of carboxylic acids (or derivatives thereof) to furnish carbon-centred radicals is proving transformative for synthetic chemistry, enabling novel and strategy-level C(sp3)–C bond disconnections with exquisite chemoselectivity. This short review will summarise several of the latest advances in this ever-expanding area.1 Introduction2 Improved Decarboxylative Arylations3 sp3–sp3 Cross-Coupling of Carboxylic Acids with Aliphatic Bromides4 sp3–sp3 Cross-Coupling of Carboxylic Acids with Aliphatic Alcohols and Amines5 Doubly Decarboxylative sp3–sp3 Cross-Coupling of Carboxylic Acids6 Decarboxylative C–C Bond Formation from (Hetero)aryl Carboxylic Acids7 Conclusions
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Visible-light-induced decarboxylative and deboronative radical addition of aliphatic carboxylic acids and arylboronic acid pinacol esters to electron-deficient alkenes using two-molecule organic photoredox catalysts, such as dibenzo[g,p]chrysene and 1,4-dicyanobenzene, proceeded efficiently to furnish radical adducts via the generation of alkyl and aryl radicals.

Abstract

Visible-light-induced decarboxylative and deboronative radical addition of aliphatic carboxylic acids and arylboronic acid pinacol esters to electron-deficient alkenes using two-molecule organic photoredox catalysts, such as dibenzo[g,p]chrysene as an electron donor and 1,4-dicyanobenzene as an electron acceptor, proceeded efficiently to furnish radical adducts via the generation of alkyl and aryl radicals. The base and substrate play important roles in this photochemical system, and the sequential photoinduced decarboxylation of glutamic acid having two different carboxy groups was successful.

Synlett
DOI: 10.1055/a-1948-6798

A ZnI2-catalyzed addition of ammonium thiocyanate to olefins in the presence of 4-toluenesulfonic acid and tetrabutylammonium iodide has been developed. The reaction proceeds by a Markovnikov-type process and a radical isomerization, and gives the corresponding isothiocyanates selectively and in good yields.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Nature Catalysis, Published online: 19 October 2022; doi:10.1038/s41929-022-00858-4

Photoexcited nickel catalysis enabled silyl-radical-mediated activation of carbamoyl chlorides. This process provides an operationally simple and widely applicable amidation reaction of a plethora of aryl and heteroaryl halides. Mechanistic understanding suggests that the reaction involves an energy-transfer mechanism for aryl bromide; while a single-electron-transfer mechanism is operating for aryl chlorides.

Abstract

Amide bonds connect the amino acids in proteins and exist as a prevalent structural motif in biomolecules. Herein, we have exploited the concept of cross-electrophile coupling by merging the photo-redox and transition-metal catalysis to construct carbamides from superabundant (hetero)aryl halides along with commercially feasible carbamoyl chlorides. The success of this method relies on the prior formation of Ni^II-aryl halide intermediates, which involves in a photoexcited Ni-halide homolysis event by energy transfer from aryl bromide and single-electron transfer from aryl chloride to assist generation of the vital carbamoyl radical. The breadth of application of this technique is demonstrated both in inter- as well as intramolecular routes for the synthesis of a plethora of (hetero)aryl carbamides with diverse functionalities, and biologically important benzolactams.

Nature, Published online: 24 August 2022; doi:10.1038/d41586-022-02213-w

Synthesis
DOI: 10.1055/a-1892-5473

Enamides, as prefunctionalized electron-rich heteroatom-substituted alkenes represent a powerful platform to synthesize useful nitrogen-containing natural products and bioactive molecules. This review discloses recent progress in the transition-metal-catalyzed enantioselective functionalization of enamides, including the Heck reaction, hydrofunctionalization, and difunctionalization, with a focus on the general scope, current limitations, stereochemical reaction control, and mechanistic aspects.1 Introduction2 Asymmetric Heck Reaction of Enamides3 Asymmetric Hydrofunctionalization of Enamides3.1 Nickel Catalysis3.2 Copper Catalysis3.3 Rhodium Catalysis3.4 Iridium Catalysis4 Asymmetric Difunctionalization of Enamides4.1 Palladium Catalysis4.2 Nickel Catalysis4.3 Copper Catalysis5 Summary and Outlook
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Publication date: 13 October 2022

Source: Chem, Volume 8, Issue 10

Author(s): Xianhong Wu, Yi Wang, Zhong-Shuai Wu

Nature, Published online: 22 August 2022; doi:10.1038/d41586-022-02297-4