Robby Vroemans

Publication date: 15 January 2022

Source: Coordination Chemistry Reviews, Volume 451

Author(s): Ishani Borthakur, Anirban Sau, Sabuj Kundu

Journal of Porphyrins and Phthalocyanines, Volume 26, Issue 01, Page 84-89, January 2022.
Herein, we report on the mechanochemical reaction of pyrrole and substituted benzaldehyde precursors to produce freebase corroles and demonstrate the one-pot mechanochemical synthesis of 5,10,15-Tris(4-[math]-butylphenyl)corrole (H[math]-buPhC), in which both, the condensation and oxidation reactions steps, took place in the ball mill. Moreover, we could achieve the mechanochemical synthesis of copper corroles with decent overall yields of 10–12%. With the mechanochemical approach we could shift the EcoScale obtained from common synthesis procedures to significant more positive values and the E-factor for the mechanochemical copper insertion was lowered by factor of 3.0.

Metal ligand cooperation. Two different iminophosphoryl-substituted methandiide-derived carbene complexes have been applied in the P−H bond activation of secondary phosphines. Surprisingly versatile reaction outcomes were observed depending on the imine substituent at the methandiide ligand and the phosphine used. While more-electron-rich combinations led to either cyclometallation or an imine transfer, electron-poor combinations enabled selective P−H bond activation, thus impressively demonstrating the importance of tuning the M=C in this type of carbene complex for bond activation.

Abstract

The use of iminophosphoryl-tethered ruthenium carbene complexes to activate secondary phosphine P−H bonds is reported. Complexes of type [(p-cymene)-RuC(SO₂Ph)(PPh₂NR)] (with R = SiMe₃ or 4-C₆H₄−NO₂) were found to exhibit different reactivities depending on the electronics of the applied phosphine and the substituent at the iminophosphoryl moiety. Hence, the electron-rich silyl-substituted complex undergoes cyclometallation or shift of the imine moiety after cooperative activation of the P−H bond across the M=C linkage, depending on the electronics of the applied phosphine. Deuteration experiments and computational studies proved that cyclometallation is initiated by the activation process at the M=C bond and triggered by the high electron density at the metal in the phosphido intermediates. Consistently, replacement of the trimethylsilyl (TMS) group by the electron-withdrawing 4-nitrophenyl substituent allowed the selective cooperative P−H activation to form stable activation products.

The first enantioselective synthesis of C7-indolino- and C7-indolo-biaryl atropisomers by means of C−H functionalisation catalysed by our chiral rhodium complex (RhJasCp) is reported. The reaction works for a wide range of substrates and gives excellent yields (up to 92 %) and very good level of enantioselectivity (up to 90 % ee). Furthermore, this transformation tolerates a variety of functional groups in both indoles and indolines.

Abstract

Axially chiral atropisomeric compounds are widely applied in asymmetric catalysis and medicinal chemistry. In particular, axially chiral indole- and indoline-based frameworks have been recognised as important heterobiaryl classes because they are the core units of bioactive natural alkaloids, chiral ligands and bioactive compounds. Among them, the synthesis of C7-substituted indole biaryls and the analogous indoline derivatives is particularly challenging, and methods for their efficient synthesis are in high demand. Transition-metal catalysis is considered one of the most efficient methods to construct atropisomers. Here, we report the enantioselective synthesis of C7-indolino- and C7-indolo biaryl atropisomers by means of C−H functionalisation catalysed by chiral RhJasCp complexes.

Two classes of tetrasubstituted axially chiral olefins have been accessed in excellent enantioselectivity via Rh^III-catalyzed asymmetric C−H activation assisted by a migratable directing group.

Abstract

Axially chiral open-chain olefins represent an underexplored class of chiral platform. In this report, two classes of tetrasubstituted axially chiral acyclic olefins have been accessed in excellent enantioselectivity and regioselectivity via C−H activation of (hetero)arenes assisted by a migratable directing group en route to coupling with sterically hindered alkynes. The coupling of indoles bearing an N-aminocarbonyl directing group afforded C–N axially chiral acrylamides with the assistance of a racemic zinc carboxylate additive. DFT studies suggest a β-nitrogen elimination–reinsertion pathway for the directing group migration. Meanwhile, the employment of N-phenoxycarboxamide delivered C−C axially chiral enamides via migration of the oxidizing directing group. Experiments suggest that in both cases the (hetero)arene substrate adopts a well-defined orientation during the C−H activation, which in turn determines the disposition of the alkyne in migratory insertion. Synthetic applications of representative chiral olefins are demonstrated.

Addressing the challenge of switching the raw material basis in plastics production from fossil to bio-based feedstocks, the synthesis of bicyclic plasticizers, which are accessible from the biorenewable compounds 2-methylfuran, maleic anhydride and 2-ethylhexanol, is presented as well as their use in performance tests. Among involved reactions are Diels-Alder reactions and hydrogenations.

Abstract

The search for more sustainable solutions for plastics production, moving away from petrochemical feedstocks as today's major raw material basis, is a research area of increasing interest. This task goes far beyond the issue of designing greener polymers and their related monomers as tailor-made plastics require, besides the polymer itself, further components. These additives also need to be switched from typically fossil-based to bio-renewable raw materials. One of such necessary components for many applications are plasticizers, and a major application of them is related to polyvinyl chloride (PVC) as one of the leading polymers with a wide range of applications. Typically today‘s plasticizers are based on fossil feedstocks, and some of them such as specific ortho-phthalates as the most important product class of plasticizers are now subject to restrictions and authorization by the EU's REACH legislation due to their toxicological profile. In this contribution, we report the synthesis and technical evaluation of alternative, novel bicyclic plasticizer candidates, which are fully accessible from renewable feedstocks. In detail, these new plasticizer target molecules are based on the use of the furan-derivative 2-methylfuran, maleic anhydride and 2-ethylhexanol as bio-based starting materials. The synthetic concept consists of an initial Diels-Alder reaction with 2-methylfuran and a subsequent hydrogenation and optional esterification step. The applied reactions are well-known as economic and sustainable technologies. Thus, not only the starting materials (being of bio-based origin) but also the selected reaction technologies for the syntheses of the target molecules are sustainable. Furthermore, a range of performance tests enabled an insight into structure-performance relationships and revealed promising plasticizing properties of this new bio-based plasticizer generation with, e. g., an attractive solution temperature fulfilling the criterium for a “fast fuser” as well as good compatibility with PVC.

Nature, Published online: 20 October 2021; doi:10.1038/d41586-021-02844-5

I turned down the role of adviser to a de-extinction company — that task belongs to everyone.

Metal nanoparticles (MNPs) and single atom catalysts (SACs) can be stabilized on porous supports including metal-organic frameworks (MOFs), graphitic carbon nitride (g-C₃N₄) and covalent organic frameworks (COFs) to enhance photocatalytic activity for environmental remediation and clean energy production.

Abstract

Photocatalysis has been known as one of the promising technologies due to its eco-friendly nature. However, the potential application of many photocatalysts is limited owing to their large bandgaps and inefficient use of the solar spectrum. One strategy to overcome this problem is to combine the advantages of heteroatom-containing supports with active metal centers to accurately adjust the structural parameters. Metal nanoparticles (MNPs) and single atom catalysts (SACs) are excellent candidates due to their distinctive coordination environment which enhances photocatalytic activity. Metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and carbon nitride (g-C₃N₄) have shown great potential as catalyst support for SACs and MNPs. The numerous combinations of organic linkers with various heteroatoms and metal ions provide unique structural characteristics to achieve advanced materials. This review describes the recent advancement of the modified MOFs, COFs and g-C₃N₄ with SACs and NPs for enhanced photocatalytic applications with emphasis on environmental remediation.

This Review summarizes significant advances in directing-group-controlled transition-metal-catalyzed selective C(sp²)−H/C(sp³)−H alkylation with maleimides. Catalysts, substrates, directing groups, reaction mechanisms, synthetic applications as well as limitations and intractable issues of this field were systematically discussed.

Abstract

Maleimides and succinimides are all vital scaffolds in biological fields and various natural products. Maleimide derivatives have been extensively used as coupling partners for various organic transformations, affording a broad array of important molecular architectures including succinimides. In the past decade, a variety of efficient chelation-assisted strategies have been employed for the selective addition of C−H bonds to maleimides giving succinimides, which are also highly important building blocks in organic synthesis. This Review provides an overview of research progress relating to maleimides participated transition-metal-catalyzed group-directed C−H alkylation from 2012 to 2021. Significant advances in this field were highlighted, diverse transition metal catalysts, organic substrates contained different directing groups, reaction mechanisms as well as synthetic applications are systematically discussed. In addition, the limitations and intractable issues need to be solved in the future are also pointed out.

Abstract

A methodology is reported for visible-light-promoted synthesis of unsymmetrical chalcogenides enabled by dimsyl anion in the absence of transition-metals or photoredox catalysts. The cross-coupling reaction between aryl halides and diaryl dichalcogenides proceeds with electron-rich, electron-poor, and heteroaromatic moieties. Mechanistic investigations using UV-Vis spectroscopy, time-dependent density functional theory (TD-DFT) calculations, and control reactions suggest that dimsyl anion forms an electron-donor-acceptor (EDA) complex capable of absorbing blue light, leading to a charge transfer responsible for generation of aryl radicals from aryl halides. This previously unreported mechanistic pathway may be applied to other light-induced transformations performed in DMSO in the presence of bases and aryl halides.