Selective Hydrogenations and Dechlorinations in Water Mediated by Anionic Surfactant-Stabilized Pd Nanoparticles

Selective hydrogenation of nitro compounds to amines by coupled redox reactions over a heterogeneous biocatalyst

Cleaner synthesis of amines remains a key challenge in organic chemistry because of their prevalence in pharmaceuticals, agrochemicals and synthetic building blocks. Here, we report a different paradigm for chemoselective hydrogenation of nitro compounds to amines, under mild, aqueous conditions. The hydrogenase enzyme releases electrons from H2 to a carbon black support which facilitates nitro-group reduction. For 30 nitroarenes we demonstrate full conversion (isolated yields 78 - 96%), with products including pharmaceuticals benzocaine, procainamide and mesalazine, and 4-aminophenol - precursor to paracetamol (acetaminophen). We also showcase gram-scale synthesis of procainamide with 90% isolated yield. We demonstrate potential for extension to aliphatic substrates. The catalyst is highly selective for reduction of the nitro group over other unsaturated bonds, tolerant to a wide range of functional groups, and exhibits excellent stability in reactions lasting up to 72 hours and full reusability over 5 cycles with a total turnover number over 1 million, indicating scope for direct translation to fine chemical manufacturing.

Advances in Nanotechnology for Enhancing the Solubility and Bioavailability of Poorly Soluble Drugs

This manuscript offers a comprehensive overview of nanotechnology's impact on the solubility and bioavailability of poorly soluble drugs, with a focus on BCS Class II and IV drugs. We explore various nanoscale drug delivery systems (NDDSs), including lipid-based, polymer-based, nanoemulsions, nanogels, and inorganic carriers. These systems offer improved drug efficacy, targeting, and reduced side effects. Emphasizing the crucial role of nanoparticle size and surface modifications, the review discusses the advancements in NDDSs for enhanced therapeutic outcomes. Challenges such as production cost and safety are acknowledged, yet the potential of NDDSs in transforming drug delivery methods is highlighted. This contribution underscores the importance of nanotechnology in pharmaceutical engineering, suggesting it as a significant advancement for medical applications and patient care.

Ph3P/ICH2CH2I-promoted reductive deoxygenation of alcohols

Owing to the ubiquity of the hydroxyl group, reductive deoxygenation of alcohols has become an active research area. The classic Barton-McCombie reaction suffers from a tedious two-step procedure. New efficient methods have been developed, but they have some limitations, such as a narrow substrate scope and the use of moisture-sensitive Lewis acids. In this work, we describe the Ph3P/ICH2CH2I-promoted reductive deoxygenation of alcohols with NaBH4. The process is applicable to benzyl, allyl and propargyl alcohols, and also to primary and secondary alcohols, demonstrating a wide substrate scope and a good level of functional group tolerance. This protocol features convenient operation and low cost of all reagents.

Metal-based Heterogeneous Catalysts for One-Pot Synthesis of Secondary Anilines from Nitroarenes and Aldehydes

Recently, N-substituted anilines have been the object of increasing research interest in the field of organic chemistry due to their role as key intermediates for the synthesis of important compounds such as polymers, dyes, drugs, agrochemicals and pharmaceutical products. Among the various methods reported in literature for the formation of C-N bonds to access secondary anilines, the one-pot reductive amination of aldehydes with nitroarenes is the most interesting procedure, because it allows to obtain diverse N-substituted aryl amines by simple reduction of nitro compounds followed by condensation with aldehydes and subsequent reduction of the imine intermediates. These kinds of tandem reactions are generally catalyzed by transition metal-based catalysts, mainly potentially reusable metal nanoparticles. The rapid growth in the last years in the field of metal-based heterogeneous catalysts for the one-pot reductive amination of aldehydes with nitroarenes demands for a review on the state of the art with a special emphasis on the different kinds of metals used as catalysts and their recyclability features.

Exhaustive Reduction of Esters Enabled by Nickel Catalysis

We report a one-step procedure to directly reduce unactivated aryl esters into their corresponding tolyl derivatives. This is achieved by an organosilane-mediated ester hydrosilylation reaction and subsequent Ni/NHC-catalyzed hydrogenolysis. The resulting conditions provide a direct and efficient alternative to multi-step procedures for this transformation that often require the use of hazardous metal hydrides. Applications in the synthesis of -CD₃-containing products, derivatization of bioactive molecules, and chemoselective reduction in the presence of other C-O bonds are demonstrated.

Novel nickel nanoparticles stabilized by imidazolium-amidinate ligands for selective hydrogenation of alkynes

Novel magnetically recoverable nickel nanoparticles (Ni NPs) stabilized by imidazolium-amidinate ligands selectively hydrogenate alkynes into (Z)-alkenes under mild conditions.

Preparation of sub-microspherical Fe3O4@PDA-Pd NPs catalyst and application in catalytic hydroreduction reaction of halogenated aromatic nitro compounds to prepare halogenated aromatic amines

Background

The side reactions of dehalogenation or C–N coupling tend to occur when halogenated aromatic amines are prepared by catalytic hydrogenation reduction of halogenated aromatic nitro compounds. In this paper, we prepared the sub-microspherical Fe₃O₄@PDA-Pd NPs catalyst apply it efficiently in the hydrogenation reduction of halogenated aromatic nitro compounds to prepare the halogenated aromatic amines under atmospheric pressure. The catalyst shows a high selectivity of greater than 96% and can effectively inhibit the occurrence of the side reactions of dehalogenation and C–N coupling.

Results

The optimum condition of the hydroreduction reaction is when tetrahydrofuran is used as solvent and the reaction happens at 50 °C for 5 h. The selectivity of the chlorinated aromatic amine and the fluorinated aromatic amine products exceed 99% and the yield exceeds 90%. Only a small amount of dehalogenated products and C–N coupling by-products were produced in the brominated aromatic compound and the iodinated aromatic compound.

Conclusion

We developed a promising method for preparing the superparamagnetic and strongly magnetic Fe₃O₄@PDA core–shell sub-microsphere-supported nano-palladium catalyst for catalyzing the hydrogenation reduction of halogenated aromatic nitro compounds. The halogenated aromatic amines were efficiently and highly selectively prepared under atmospheric pressure, with the side reactions of dehalogenation and C–N coupling effectively inhabited simultaneously.

Mild and efficient rhodium-catalyzed deoxygenation of ketones to alkanes

Chlorodicarbonylrhodium(i) dimer: a simple catalyst for the reduction of carbonyl compounds also.