Efficient carbon dioxide hydrogenation to formic acid with buffering ionic liquids

The efficient transformation of CO2 into chemicals and fuels is a key challenge for the decarbonisation of the synthetic production chain. Formic acid (FA) represents the first product of CO2 hydrogenation and can be a precursor of higher added value products or employed as a hydrogen storage vector. Bases are typically required to overcome thermodynamic barriers in the synthesis of FA, generating waste and requiring post-processing of the formate salts. The employment of buffers can overcome these limitations, but their catalytic performance has so far been modest. Here, we present a methodology utilising IL as buffers to catalytically transform CO2 into FA with very high efficiency and comparable performance to the base-assisted systems. The combination of multifunctional basic ionic liquids and catalyst design enables the synthesis of FA with very high catalytic efficiency in TONs of >8*105 and TOFs > 2.1*104 h−1

Expanding Ligand Space: Preparation, Characterization, and Synthetic Applications of Air-Stable, Odorless Di-tert-alkylphosphine Surrogates

The di-tert-alkylphosphino motif is common to many best-in-class ligands for late-transition-metal catalysis. However, the structural diversity of these privileged substructures is currently limited by the need to manipulate highly toxic, highly reactive reagents and intermediates in their synthesis. In response to this longstanding challenge, we report an umpolung strategy for the synthesis of structurally diverse di-tert-alkylphosphine building blocks via SN1 alkylation of in situ generated PH3 gas. We show that the products—which are isolated as air-stable, odorless phosphonium salts—can be used directly in the preparation of key synthetic intermediates and ligand classes. The di-tert-alkylphosphino building blocks that are accessible using our methodology therefore enable facile expansion of extant ligand classes by modification of a previously invariant vector; we demonstrate that these modifications affect the steric and electronic properties of the ligands and can be used to tune their performance in catalysis

Enantioselective nickel-catalyzed arylative and alkenylative intramolecular 1,2-allylations of tethered allene–ketones

The enantioselective nickel-catalyzed reaction of tethered allene–ketones with (hetero)arylboronic acids or potassium vinyltrifluoroborate is described. Carbonickelation of the allene gives allylnickel species, which undergo cyclization by 1,2-allylation to produce chiral tertiary-alcohol-containing aza- and carbocycles in high diastereo- and enantioselectivities

Gold(I)-Catalyzed Nucleophilic Allylation of Azinium Ions with Allylboronates

Gold(I)-catalyzed nucleophilic allylations of pyridinium and quinolinium ions with allylboronates are reported. Transmetalation of the allylboronate with gold produces nucleophilic allylgold(I) species that add to the 4-position of the azinium ion with complete regioselectivity to give functionalized 1,4-dihydropyridines and 1,4-dihydroquinolines. Density functional theory (DFT) calculations provided mechanistic insight

Enantioselective nickel-catalyzed anti-arylmetallative cyclizations onto acyclic electron-deficient alkenes

Enantioselective nickel-catalyzed reactions of (hetero)arylboronic acids or alkenylboronic acids with substrates containing an alkyne tethered to various acyclic electron-deficient alkenes are described

Catalytic enantioselective arylative cyclizations of alkynyl 1,3-diketones by 1,4-rhodium(i) migration

The enantioselective synthesis of densely functionalized polycarbocycles by the rhodium(I)-catalyzed reaction of arylboronic acids with 1,3-diketones is described. The key step in these desymmetrizing domino addition–cyclization reactions is an alkenyl-to-aryl 1,4-Rh(I) migration, which enables arylboronic acids to function effectively as 1,2-dimetalloarene surrogates

Catalyst-free hydrophosphinylation of isocyanates and isothiocyanates under low-added-solvent conditions

A catalyst-free, low-solvent method for the hydrophosphinylation of isocyanates and isothiocyanates is reported. A range of phosphorus nucleophiles including secondary phosphine oxides HP(O)R2 (R = Ph, iPr), phosphites HP(O)(OR)2 (R = Me, Et), and methyl phenylphosphinate were tested. The procedure tolerated isocyanates and isothiocyanates featuring a wide range of substituents and, with use of 4 equiv of 2-methyltetrahydrofuran (2-MeTHF), solid substrates can be utilized. Twenty-five compounds were prepared with improved functional group tolerance compared to previous methods allowing access to new compounds (16 are novel). Facile scale up and simple reaction conditions make this a straightforward and practical methodology for obtaining phosphorus analogues of ureas and thioureas, which are challenging to synthesize by other methods

Catalyst-free Hydrophosphinylation of Isocyanates and Isothiocyanates under Low-Added-Solvent Conditions

A catalyst-free, low-solvent method for the hydrophosphinylation of isocyanates and isothiocyanates is reported. A range of phosphorus nucleophiles including secondary phosphine oxides HP(O)R2 (R = Ph, i Pr), phosphites HP(O)(OR)2 (R = Me, Et), and methyl phenylphosphinate are tested. The procedure tolerates isocyanates and isothiocyanates featuring a wide range of substituents and, by using four equivalents of 2-methyltetrahydrofuran (2-MeTHF), solid substrates can be utilized. Twenty-five compounds are prepared, with improved functional group tolerance compared to previous methods and allowing access to new compounds (16 are novel). Facile scale up and simple reaction conditions make this a straightforward and practical methodology for obtaining phosphorus analogues of ureas and thioureas, which are challenging to synthesize by other methods

Group 11 m-Terphenyl Complexes Featuring Metallophilic Interactions

A series of group 11 m-terphenyl complexes have been synthesized via a metathesis reaction from the iron(II) complexes (2,6-Mes2C6H3)2Fe and (2,6-Xyl2C6H3)2Fe (Mes = 2,4,6-Me3C6H2; Xyl = 2,6-Me2C6H3). [2,6-Mes2C6H3M]2 (1, M = Cu; 2, M = Ag; 6, M = Au) and [2,6-Xyl2C6H3M]2 (3, M = Cu; 4, M = Ag) are dimeric in the solid state, although different geometries are observed depending on the ligand. These complexes feature short metal–metal distances in the expected range for metallophilic interactions. While 1–4 are readily isolated using this metathetical route, the gold complex 6 is unstable in solution at ambient temperatures and has only been obtained in low yield from the decomposition of (2,6-Mes2C6H3)Au·SMe2 (5). NMR spectroscopic measurements, including diffusion-ordered spectroscopy, suggest that 1–4 remain dimeric in a benzene-d6 solution. The metal–metal interactions have been examined computationally using the Quantum Theory of Atoms in Molecules and by an energy decomposition analysis employing natural orbitals for chemical valence

Asymmetric Construction of Alkaloids Employing a Key ω-Transaminase Cascade

An ω‐transaminase triggered intramolecular aza‐Michael reaction has been employed for the preparation of cyclic β‐enaminones in good yield and excellent enantio‐ and diastereoselectivity, starting from easily accessible prochiral ketoynones and commercially available enzymes. The powerful thermodynamic driving force associated with the spontaneous aza‐Michael reaction effectively displaces the transaminase reaction equilibrium towards product formation, using only two equivalents of isopropylamine. To demonstrate the potential of this methodology, we have combined this biocatalytic aza‐Michael step with annulation chemistry, affording unique stereo‐defined fused alkaloid architectures