Robby Vroemans

Abstract

Herein, we describe an isolable, air-stable, homogeneous, nickel catalyst that performs dehydrogenative cross-coupling reaction between secondary and primary alcohols to result α-alkylated ketone products selectively. The sequence of steps involve in this one-pot reaction is dehydrogenation of both alcohols, condensation between the ketone and the aldehyde, and hydrogenation of the in situ-generated α,β-unsaturated ketone. Preliminary mechanistic investigation hints a radical mechanism following borrowing hydrogen reaction.

Synlett 2021;
DOI: 10.1055/s-0037-1612268

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© Georg Thieme Verlag Stuttgart · New York

Article in Thieme eJournals:
Table of contents  |  Abstract

Synlett
DOI: 10.1055/a-1608-5633

Organic photoredox catalysts with a long excited-state lifetime have emerged as promising alternatives to transition-metal-complex photocatalysts. This paper explains the effectiveness of using long-lifetime photoredox catalysts for organic transformations, focusing on the structures and photophysics that enable long excited-state lifetimes. The electrochemical potentials of the reported organic, long-lifetime photocatalysts are compiled and compared with those of the representative Ir(III)- and Ru(II)-based catalysts. This paper closes by providing recent demonstrations of the synthetic utility of the organic catalysts.1 Introduction2 Molecular Structure and Photophysics3 Photoredox Catalysis Performance4 Catalysis Mediated by Long-Lifetime Organic Photocatalysts4.1 Photoredox Catalytic Generation of a Radical Species and its Addition to Alkenes4.2 Photoredox Catalytic Generation of a Radical Species and its Addition to Arenes4.3 Photoredox Catalytic Generation of a Radical Species and its Addition to Imines4.4 Photoredox Catalytic Generation of a Radical Species and its Addition to Substrates Having C≡X Bonds (X=C, N)4.5 Photoredox Catalytic Generation of a Radical Species and its Bond Formation with Transition Metals4.6 Miscellaneous Reactions of Radical Species Generated by Photoredox Catalysis5 Conclusions
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
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This review summarizes the synthesis of several porous organic polymers (POPs) that can be used for CO₂ catalytic conversion, systematically listing the progress of heterogeneous metal-supported POPs catalysts in CO₂ catalytic conversion and summarizes the current challenges in this field. Finally, the prospects of catalysts for ideal catalytic conversion of CO₂ in the future is mentioned.

Abstract

To overcome the challenges of global warming and environmental pollution, it is necessary to reduce the concentration of carbon dioxide (CO₂) in the atmosphere, which is mainly accumulated in the air through the burning of fossil fuels. Therefore, the development of environmentally friendly strategies to capture carbon dioxide and convert it into value-added products offers a promising way forward for reducing carbon dioxide concentration in the atmosphere. In this context, POPs (porous organic polymers) have shown great potential as CO₂ selective adsorbents due to their high specific surface area, chemical stability, nanoscale porosity and structural diversity, as well as POPs based heterogeneous catalysts for CO₂ conversion. This review provides a concise account of preparation methods of various POPs, challenges and current development trends of POPs in photocatalytic CO₂ reduction, electrocatalytic CO₂ reduction and chemical CO₂ conversion.

Nature, Published online: 29 September 2021; doi:10.1038/d41586-021-02585-5

Homogeneous catalysts based on ruthenium and manganese enable the generation of gaseous CO and H₂ (syngas) from conveniently storable and easily transportable methanol. Conversion/time profiles and kinetic isotope effects together with spectroscopically detected intermediates indicate rapid dehydrogenation followed by two possible catalytic pathways via formaldehyde or methyl formate for decarbonylation as mechanistic manifold.

Abstract

The acceptorless dehydrogenation of methanol to carbon monoxide and hydrogen was investigated using homogeneous molecular complexes. Complexes of ruthenium and manganese comprising the MACHO ligand framework showed promising activities for this reaction. The molecular ruthenium complex [RuH(CO)(BH₄)(HN(C₂H₄PPh₂)₂)] (Ru-MACHO-BH) achieved up to 3150 turnovers for carbon monoxide and 9230 turnovers for hydrogen formation at 150 °C reaching pressures up to 12 bar when the decomposition was carried out in a closed vessel. Control experiments affirmed that the metal complex mediates the initial fast dehydrogenation of methanol to formaldehyde and methyl formate followed by subsequent slow decarbonylation. Depending on the catalyst and reaction conditions, the CO/H₂ ratio in the gas mixture thus varies over a broad range from almost pure hydrogen to the stoichiometric limit of 1:2.

β-Keto amides are versatile building-blocks in organic chemistry. This Review summarized the up-to-date advancement in the synthesis and reactivities of β-keto amides and their applications for heterocycle constructions and coordination chemistry. A special focus is given to the enlightening developments under the background of transition-metal- and organocatalysis.

Abstract

β-Keto amides are a versatile class of compounds that find wide applications in organic chemistry owing to the juxtaposition of multiple reaction sites within their molecular structures. Due to the importance of β-keto amides in modern organic chemistry, numerous novel preparation methods, synthetic applications and unprecedented reactivities have been recorded over the past decade. Taking advantage of transition-metal-catalysis and organocatalysis, β-keto amides have emerged into a jack-of-all-trades building block for many stereoselective or tandemized multicomponent reactions. But so far, no reviews have been documented on these recent achievements with β-keto amides. Our Review aims to provide a thorough summary regarding: (a) the synthesis of β-keto amides, (b) the reactivities of β-keto amides, (c) the synthetic applications of β-keto amides in various important heterocyclic compounds, and (d) the coordination of β-keto amides with main group elements and transition metals and the relevant applications.

Nature, Published online: 29 September 2021; doi:10.1038/d41586-021-02624-1

Nature, Published online: 28 September 2021; doi:10.1038/d41586-021-02612-5