Hydration of terminal alkynes catalyzed by a water-soluble salen-Co(III) complex

Integrating Au Catalysis and Engineered Amine Dehydrogenase for the Chemoenzymatic Synthesis of Chiral Aliphatic Amines

Direct synthesis of aliphatic amines from alkynes is highly desirable due to its atom economy and high stereoselectivity but still challenging, especially for the long-chain members. Here, a combination of Au-catalyzed alkyne hydration and amine dehydrogenase-catalyzed (AmDH) reductive amination was constructed, enabling sequential conversion of alkynes into chiral amines in aqueous solutions, particularly for the synthesis of long-chain aliphatic amines on a large scale. The production of chiral aliphatic amines with more than 6 carbons reached 36-60 g/L. A suitable biocatalyst [PtAmDH (A113G/T134G/V294A)], obtained by data mining and active site engineering, enabled the transformation of previously inactive long-chain ketones at high concentrations. Computational analysis revealed that the broader substrate scope and tolerance with the high substrate concentrations resulted from the additive effects of mutations introduced to the three gatekeeper residues 113, 134, and 294.

FeIII -Based Eutectic Mixtures as Multi-task and Reusable Reaction Media for Efficient and Selective Conversion of Alkynes into Carbonyl Compounds

An efficient, simple and general protocol for the selective hydration of terminal alkynes into the corresponding methyl ketones has been developed by using a cheap, easy-to-synthesise and sustainable FeIII -based eutectic mixture [FeCl3  ⋅ 6H2 O/Gly (3 : 1)] as both promoter and solvent for the hydration reaction, working: i) under mild (45 °C) and bench-type reaction conditions (air); and ii) in the absence of ligands, co-catalysts, co-solvents or toxic, non-abundant and expensive noble transition metals (Au, Ru, Pd). When the final methyl ketones are solid/insoluble in the eutectic mixture, the hydration reaction takes place in 30 min, and the obtained methyl ketones can be isolated by simply decanting the liquid FeIII -DES, allowing the direct isolation of the desired ketones without VOC solvents. By using this straightforward and simple isolation protocol, we have been able to recycle the FeIII -based eutectic mixture system up to eight consecutive times. Furthermore, the FeIII -eutectic mixture is able to promote the selective and efficient formal oxidation of internal alkynes into 1,2-diketones, with the possibility of recycling this system up to three consecutive times. Preliminary investigations into a possible mechanism for the oxidation of the internal alkynes seem to indicate that it proceeds through the formation of the corresponding methyl ketones and α-chloroketones.

Synthesis of a Novel Magnetically Retrievable Nanocomposite with Au Nanocatalysts for Hydration Reaction

Developing efficient catalysts with good recyclability is of great importance for its practical applications. In this study, a novel magnetically retrievable nanocomposite (Au-SiO2@Fe3O4-RGO) was synthesized for catalyzing hydration reaction. Active Au nanoparticles are deposited on core-shell SiO2@Fe3O4, which are further supported by a two-dimensional reduced graphene oxide (RGO) platform. The prepared Au-SiO2@Fe3O4-RGO was proven to be efficient as well as recyclable. An excellent catalytic performance, with 97% yield towards the hydration of phenylacetylene, was achieved for the catalyst in dioxane. Remarkably, the catalyst can be readily recycled through magnetic separation and achieved superior catalyst recovery and stability after seven cycles without any metal leaching. This work provides a strategy to fabricate recyclable and durable catalysts for industrial applications.

Gold nanoparticles supported on layered TiO2–RGO hybrid as an enhanced and recyclable catalyst for microwave-assisted hydration reaction

A novel composite (Au–SO₄²⁻/TiO₂–RGO) is synthesized and serves as an enhanced catalyst for alkyne hydration.