Robby Vroemans

This work presents a flexible, straightforward methodology to synthesize phosphonamidates starting from commonly available phosphonates, and demonstrates the use of phosphonylaminium salts to mediate the harsh reactivity of phosphonochloridates. Our methodology is demonstrated on primary amines, secondary amines, ammonium acetate, aniline derivatives and different phosphonate diesters.

Abstract

Organophosphorus compounds such as phosphonamidates are gaining attention across different fields of chemistry, with interesting applications as pharmaceuticals, or pesticides. However, practical application of phosphonamidates is complicated by their difficult syntheses which often involve expensive or unstraightforward reagents and harsh conditions. To remedy these issues, we present a flexible, room temperature synthesis for novel P-alkylphosphonamidates without the need for intermediary purification. Commonly available phosphonates are first chlorinated by use of oxalyl chloride and phosphonylaminium salts are used to mediate the harsh reactivity of phosphonochloridates, giving rise to the desired products. We demonstrate the compatibility of our protocol with primary and secondary amines, as well as with different phosphonate esters. The proposed pathway also enables the synthesis of primary phosphonamidates using ammonium acetate as a cheap and safe alternative for ammonia. In future research, this protocol will also enable the synthesis of bioactive targets that are incompatible with current protocols.

Even at the ppm level, sulfur poisoning and regeneration are challenges for metal nanoparticle catalysts, but little is known about single-metal-site catalysts. Herein, we describe the unique character of single-site catalysts (Rh₁/POPs) that suffer from H₂S poisoning, but could self-recover and be regenerated by simply withdrawing the H₂S. The corresponding Rh nanoparticle demonstrated poor activity and could not be regenerated.

Abstract

Sulfur poisoning and regeneration are global challenges for metal catalysts even at the ppm level. The sulfur poisoning of single-metal-site catalysts and their regeneration is worthy of further study. Herein, sulfur poisoning and self-recovery are first presented on an industrialized single-Rh-site catalyst (Rh₁/POPs). A decreased turnover frequency of Rh₁/POPs from 4317 h⁻¹ to 318 h⁻¹ was observed in a 1000 ppm H₂S co-feed for ethylene hydroformylation, but it self-recovered to 4527 h⁻¹ after withdrawal of H₂S, whereas the rhodium nanoparticles demonstrated poor activity and self-recovery ability. H₂S reduced the charge density of the single Rh atom and lowered its Gibbs free energy with the formation of inactive (SH)Rh(CO)(PPh₃-frame)₂, which could be regenerated to active HRh(CO)(PPh₃-frame)₂ after withdrawing H₂S. The mechanism and the sulfur-related structure–activity relationship were highlighted. This work provides an understanding of heterogeneous ethylene hydroformylation and sulfur-poisoned regeneration in the science of single-atom catalysts.

Publication date: 15 August 2023

Source: Coordination Chemistry Reviews, Volume 489

Author(s): Pep Rojo, Antoni Riera, Xavier Verdaguer

A nickel-catalyzed heteroarene C−H/arenol C−OH coupling reaction is reported, which omits the use of strong Lewis-acid additive and low atom-economy protecting reagent. Arrays of arenols and heteroarenes are effective in this protocol using the in-situ activating reagent pivalic anhydride.

Abstract

Increasing sustainability awareness throughout society has sought to bring more atom-economy and environmentally benign synthetic methods based on simultaneous reaction transformation through ubiquitous C−H and C−O activation. This work reports a Ni-catalyzed heteroarene C−H/arenol C−OH coupling reaction, which omits the use of strong Lewis-acid additive and low atom-economy protecting reagent. The array of arenols and heteroarenes is effective in this protocol using in-situ activating reagent of pivalic anhydride. Detailed mechanistic studies and identification of intermediate have been carried out to understand the nature of catalytic reactions.

Abstract

A copper-catalyzed N-alkylation of NH-sulfoximines with alkyl diacyl peroxides under blue light LED irradiation is reported. The process has a good functional group tolerance, and the products are obtained in yields ranging from 45–91%.

Catalytic amounts of Zn-MOF-74 promoted the aldol condensation in a cobalt-catalyzed hydroformylation reaction. The investigation of the system showed that the cobalt catalyst and Zn-MOF-74 facilitate the aldol condensation in a cooperative fashion. Zn-MOF-74 activates the aldehyde product by adsorption, as shown by DFT.

Abstract

The tandem hydroformylation-aldol condensation (tandem HF-AC) reaction offers an efficient synthetic route to the synthesis of industrially relevant products. The addition of Zn-MOF-74 to the cobalt-catalyzed hydroformylation of 1-hexene enables tandem HF-AC under milder pressure and temperature conditions than the aldox process, where zinc salts are added to cobalt-catalyzed hydroformylation reactions to promote aldol condensation. The yield of the aldol condensation products increases by up to 17 times compared to that of the homogeneous reaction without MOF and up to 5 times compared to the aldox catalytic system. Both Co₂(CO)₈ and Zn-MOF-74 are required to significantly enhance the activity of the catalytic system. Density functional theory simulations and Fourier-transform infrared experiments show that heptanal, the product of hydroformylation, adsorbs on the open metal site (OMS) of Zn-MOF-74, thereby increasing the electrophilic character of the carbonyl carbon atom and facilitating the condensation.

The Cover Feature illustrates the crucial role of storage conditions of silica-gel-supported 2nd generation Hoveyda-Grubbs catalyst. The glass shield on the spaceship protects the catalyst from air and moisture. In their Research Article, C. R. Apesteguía, S. E. Vaillard and co-workers show that after exposure to atmospheric conditions, O₂ and H₂O degrade the immobilized catalyst, compromising its applicability in olefin metathesis reactions. In order to retain long term stability the catalyst should be stored under controlled conditions. More information can be found in the Research Article by C. R. Apesteguía, S. E. Vaillard and co-workers.

Publication date: 8 June 2023

Source: Chem, Volume 9, Issue 6

Author(s): Jian-Jun Li, Jia-Hui Zhao, Hua-Chen Shen, Kevin Wu, Xin Kuang, Peng Wang, Jin-Quan Yu

Publication date: 1 August 2023

Source: Coordination Chemistry Reviews, Volume 488

Author(s): Muhammad Humayun, Muhammad Israr, Zhishan Li, Wei Luo, Chundong Wang

“Supported Metal Single Atom Catalysis”, edited by Philippe Serp and Doan Pham Minh, covers all key aspects of supported metal single atom catalysts, an invaluable resource for academic researchers and industry professionals alike. For more information: see the Wiley homepage.

Abstract

“Supported Metal Single Atom Catalysis”, edited by Philippe Serp and Doan Pham Minh, covers all key aspects of supported metal single atom catalysts, an invaluable resource for academic researchers and industry professionals alike. For more information: https://www.wiley.com/en-gb/9783527830176

Single Atom Catalysts: Metal salts, complexes and nanoparticles can evolve in solution to catalytically active single atoms and clusters, which can be incorporated onto solids (such as single atom catalysts, SACs) to perform key organic reactions in a more sustainable and, many times, efficient way.

Abstract

The supporting of pre-formed soluble metal catalysts on solids is a typical methodology to transform soluble but unrecoverable metal complexes into recoverable and reusable solid catalysts. However, this methodology has been barely implemented for ligand-less, bare single metal atoms (SMAs) and nanoclusters (NCs) in organic synthesis, despite these ultrasmall species can be formed in-situ during reaction and be the truly catalytic species. The aim of this review is to explore how to speciate active single metal atoms and clusters during homogeneous catalysis (in solution), without ligands, and to prepare them independently, to be transferred to solid supports and catalyze organic reactions. In many cases, the translation to solids gives single atom catalysts (SACs). Supporting of ultrasmall metal aggregates gives more stable, reusable and, sometimes, chemoselective catalysts for representative organic reactions.

Heteroatom-carbonyl fluorides have been confirmed as an important class of building blocks for the preparation of useful molecules in organic chemistry. The recent advances in the synthesis and typical application of carbamoyl fluorides, fluoroformates, and their analogues by the halide exchanges and the fluorocarbonylation reactions using O/S/Se=CF₂ reagents or their equivalents are summarized in this review.

Abstract

Carbamoyl fluorides, fluoroformates, and their analogues are a class of important compounds and have been evidenced as versatile building blocks for the preparation of useful molecules in organic chemistry. While major achievements were made in the synthesis of carbamoyl fluorides, fluoroformates, and their analogues in the last half of 20^th century, an increasing number of reports have focused on using O/S/Se=CF₂ species or their equivalents as the fluorocarbonylation reagents for the direct construction of these compounds from the parent heteroatom-nucleophiles in recent years. This review mainly summarizes the advances in the synthesis and typical application of carbamoyl fluorides, fluoroformates, and their analogues by the halide exchanges and fluorocarbonylation reactions since 1980.

Synthesis
DOI: 10.1055/a-2065-5802

A reductive coupling reaction of sodium sulfinates for the synthesis of symmetrical/unsymmetrical thiosulfonates is developed. The reaction takes place in the presence of acetyl chloride and Hantzsch ester under mild conditions and exhibits broad functional group tolerance. Mechanistic studies suggest that a radical process is involved.
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Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text

Remote 1,4-difunctionalization of methylenecyclobutanols was accomplished by C−C cleavage to release ring strain, selectively affording γ,δ-unsaturated aldehydes. The photocatalyzed reaction proceeds in good yields, and was used for the concise synthesis of the natural product alatanone A.

Abstract

Radical additions onto olefins have surfaced as an increasingly powerful strategy for the synthesis of difunctionalized scaffolds. However, despite of major advances, known approaches continue to be largely limited to two manifolds, namely 1,2-difunctionalization of alkenes and remote difunctionalization via hydrogen atom transfer (HAT). Herein, we describe a mechanistically distinct approach by photoinduced carbon-carbon (C−C) activation/ring-opening to access γ,δ-unsaturated aldehydes from methylenecyclobutanols and sulfonyl chlorides by strain release. Remarkably, the sulfonyl motif on the products was easily removed by another photocatalytic process, which enabled the concise assembly of the natural product alatanone A. The synthetic utility of our approach was reflected by versatile functional group tolerance, ample substrate scope, and scalability. The photocatalysis represents a conceptually distinct alternative to existing approaches for remote 1,4-diversifications, with a double bond remaining in the thus obtained products.