Highly Enantioselective Pd-Catalyzed Asymmetric Hydrogenation of Activated Imines

Pd/bisphosphines complexes are highly effective catalysts for asymmetric hydrogenation of activated imines in trifluoroethanol. The asymmetric hydrogenation of N-diphenylphosphinyl ketimines 3 with Pd(CF3CO2)/(S)-SegPhos indicated 87−99% ee, and N-tosylimines 5 could gave 88−97% ee with Pd(CF3CO2)/(S)-SynPhos as a catalyst. Cyclic N-sulfonylimines 7 and 11 were hydrogenated to afford the useful chiral sultam derivatives in 79−93% ee, which are important organic synthetic intermediates and structural units of agricultural and pharmaceutical agents

Palladium-Catalyzed Asymmetric Hydrogenation of Functionalized Ketones

A novel catalytic system for asymmetric hydrogenation of functionalized ketones has been developed using a Pd/bisphosphine complex as the catalyst in 2,2,2-trifluoroethanol. The reaction exhibits high enantioselectivity, and up to 92.2% ee was obtained

Hydrogenation of Alkyl Carboxylic Acids with Tetrahydropyrimidine-Derived Iridium Complexes under Mild Conditions

The hydrogenation of carboxylic acids to alcohols is of great significance in synthetic chemistry. Reported herein are competent iridium catalysts [Cp*Ir­(N,N′)­(H2O)]­[OTf]2 (N,N′ = three different 2,2′-bi-1,4,5,6-tetrahydropyrimidines) for application in the catalytic hydrogenation of a series of alkyl carboxylic acids under mild conditions (25–100 °C) without any additives. Among these structurally diverse catalysts evaluated for reactivity, complex 4 bearing an electron-deficient ligand (N,N′ = 2,2′-bi-5,5′-hydroxyl-1,4,5,6-tetrahydropyrimidine) is the most robust, which can hydrogenate acetic acid smoothly at 25 °C to give the alcohol and ester products with a TON of 1106. Detailed mechanistic studies suggest that the generation of an [Ir–H] intermediate is involved in the rate-limiting step. With this catalyst system, a broad range of alkyl carboxylic acids were hydrogenated with moderate to high TONs

Hydrogenation of Alkyl Carboxylic Acids with Tetrahydropyrimidine-Derived Iridium Complexes under Mild Conditions

The hydrogenation of carboxylic acids to alcohols is of great significance in synthetic chemistry. Reported herein are competent iridium catalysts [Cp*Ir­(N,N′)­(H2O)]­[OTf]2 (N,N′ = three different 2,2′-bi-1,4,5,6-tetrahydropyrimidines) for application in the catalytic hydrogenation of a series of alkyl carboxylic acids under mild conditions (25–100 °C) without any additives. Among these structurally diverse catalysts evaluated for reactivity, complex 4 bearing an electron-deficient ligand (N,N′ = 2,2′-bi-5,5′-hydroxyl-1,4,5,6-tetrahydropyrimidine) is the most robust, which can hydrogenate acetic acid smoothly at 25 °C to give the alcohol and ester products with a TON of 1106. Detailed mechanistic studies suggest that the generation of an [Ir–H] intermediate is involved in the rate-limiting step. With this catalyst system, a broad range of alkyl carboxylic acids were hydrogenated with moderate to high TONs

Hydrogenation of Alkyl Carboxylic Acids with Tetrahydropyrimidine-Derived Iridium Complexes under Mild Conditions

The hydrogenation of carboxylic acids to alcohols is of great significance in synthetic chemistry. Reported herein are competent iridium catalysts [Cp*Ir­(N,N′)­(H2O)]­[OTf]2 (N,N′ = three different 2,2′-bi-1,4,5,6-tetrahydropyrimidines) for application in the catalytic hydrogenation of a series of alkyl carboxylic acids under mild conditions (25–100 °C) without any additives. Among these structurally diverse catalysts evaluated for reactivity, complex 4 bearing an electron-deficient ligand (N,N′ = 2,2′-bi-5,5′-hydroxyl-1,4,5,6-tetrahydropyrimidine) is the most robust, which can hydrogenate acetic acid smoothly at 25 °C to give the alcohol and ester products with a TON of 1106. Detailed mechanistic studies suggest that the generation of an [Ir–H] intermediate is involved in the rate-limiting step. With this catalyst system, a broad range of alkyl carboxylic acids were hydrogenated with moderate to high TONs

Hydrogenation of Alkyl Carboxylic Acids with Tetrahydropyrimidine-Derived Iridium Complexes under Mild Conditions

The hydrogenation of carboxylic acids to alcohols is of great significance in synthetic chemistry. Reported herein are competent iridium catalysts [Cp*Ir­(N,N′)­(H2O)]­[OTf]2 (N,N′ = three different 2,2′-bi-1,4,5,6-tetrahydropyrimidines) for application in the catalytic hydrogenation of a series of alkyl carboxylic acids under mild conditions (25–100 °C) without any additives. Among these structurally diverse catalysts evaluated for reactivity, complex 4 bearing an electron-deficient ligand (N,N′ = 2,2′-bi-5,5′-hydroxyl-1,4,5,6-tetrahydropyrimidine) is the most robust, which can hydrogenate acetic acid smoothly at 25 °C to give the alcohol and ester products with a TON of 1106. Detailed mechanistic studies suggest that the generation of an [Ir–H] intermediate is involved in the rate-limiting step. With this catalyst system, a broad range of alkyl carboxylic acids were hydrogenated with moderate to high TONs

Hydrogenation of Alkyl Carboxylic Acids with Tetrahydropyrimidine-Derived Iridium Complexes under Mild Conditions

The hydrogenation of carboxylic acids to alcohols is of great significance in synthetic chemistry. Reported herein are competent iridium catalysts [Cp*Ir­(N,N′)­(H2O)]­[OTf]2 (N,N′ = three different 2,2′-bi-1,4,5,6-tetrahydropyrimidines) for application in the catalytic hydrogenation of a series of alkyl carboxylic acids under mild conditions (25–100 °C) without any additives. Among these structurally diverse catalysts evaluated for reactivity, complex 4 bearing an electron-deficient ligand (N,N′ = 2,2′-bi-5,5′-hydroxyl-1,4,5,6-tetrahydropyrimidine) is the most robust, which can hydrogenate acetic acid smoothly at 25 °C to give the alcohol and ester products with a TON of 1106. Detailed mechanistic studies suggest that the generation of an [Ir–H] intermediate is involved in the rate-limiting step. With this catalyst system, a broad range of alkyl carboxylic acids were hydrogenated with moderate to high TONs

In Situ Electrodeposited Indium Nanocrystals for Efficient CO₂ Reduction to CO with Low Overpotential

The dream of artificial photosynthesis that converts CO₂ to fuels or chemicals has been dimmed by the lack of efficient catalysts. Herein, an indium (In)-based catalyst is prepared via in situ electrodeposition on a carbon substrate from an organometallic precursor during the CO₂ reduction reaction. It is found to be robust for CO₂ reduction to CO promoted by imidazolium ionic liquid in acetonitrile. The onset overpotential is impressively low for a non-noble-metal material, rivaling that of the noble metal Ag. Moreover, the CO evolution rate is stable for 15 h, with a Faradaic efficiency of around 99%. Under the same conditions, In catalyst deposited in situ performs much better than that prepared ex situ and most of the catalysts previously reported. This is ascribed to the intrinsic properties of in situ generated In nanocrystals in good contact with the porous substrate, suggesting the advantages of the in situ preparation strategy. In addition, via coupling the CO₂ reduction reaction with water oxidation in aqueous anolyte, CO and O₂ can be produced simultaneously with high efficiency, demonstrating the good performance of the non-noble-metal In-based catalyst for reducing CO₂ to CO and its possible application in artificial photosynthesis from water and CO₂

Highly Enantioselective Iridium-Catalyzed Hydrogenation of Heteroaromatic Compounds, Quinolines

The highly enantioselective hydrogenation of quinoline derivatives is developed using [Ir(COD)Cl]2/(R)-MeO-Biphep/I2 system, and this methodology has been applied to the asymmetric synthesis of three naturally occurring alkaloids angustureine, galipinine, and cuspareine. This method provided an efficient access to a variety of optically active tetrahydroquinolines with up to 96% ee

Highly Enantioselective Iridium-Catalyzed Hydrogenation of 2-Benzylquinolines and 2-Functionalized and 2,3-Disubstituted Quinolines

The enantioselective hydrogenation of 2-benzylquinolines and 2-functionalized and 2,3-disubstituted quinolines was developed by using the [Ir(COD)Cl]2/bisphosphine/I2 system with up to 96% ee. Moreover, mechanistic studies revealed the hydrogenation mechanism of quinoline involves a 1,4-hydride addition, isomerization, and 1,2-hydride addition, and the catalytic active species may be a Ir(III) complex with chloride and iodide