Deoxygenation of Sulfoxides to Sulfides in the Presence of Zinc Catalysts and Boranes as Reducing Reagents

Reduction of sulfoxides catalyzed by the commercially available manganese complex MnBr(CO)5

A new methodology for the reduction of a wide variety of aliphatic and aromatic sulfoxides catalyzed by the air-stable, cheap and commercially available manganese catalyst MnBr(CO)5 with excellent yields is reported in this work. The catalytic system MnBr(CO)5/PhSiH3 is highly chemoselective, allowing the effective reduction of the SO bond in the presence of different functional groups.

Phosphorus-Alloying as a Powerful Method for Designing Highly Active and Durable Metal Nanoparticle Catalysts for the Deoxygenation of Sulfoxides: Ligand and Ensemble Effects of Phosphorus

The modification of metal nanoparticles (NPs) by incorporating additional metals is a key technique for developing novel catalysts. However, the effects of incorporating nonmetals into metal NPs have not been widely explored, particularly in the field of organic synthesis. In this study, we demonstrate that phosphorus (P)-alloying significantly increases the activity of precious metal NPs for the deoxygenation of sulfoxides into sulfides. In particular, ruthenium phosphide NPs exhibit an excellent catalytic activity and high durability against sulfur-poisoning, outperforming conventional catalysts. Various sulfoxides, including drug intermediates, were deoxygenated to sulfides with excellent yields. Detailed investigations into the structure-activity relationship revealed that P-alloying plays a dual role: it establishes a ligand effect on the electron transfer from Ru to P, facilitating the production of active hydrogen species, and has an ensemble effect on the formation of the Ru-P bond, preventing strong coordination with sulfide products. These effects combine to increase the catalytic performance of ruthenium phosphide NPs. These results demonstrate that P-alloying is an efficient method to improve the metal NP catalysis for diverse organic synthesis.

A DFT examination of the role of proximal boron functionalities in the S-alkylation of sulfenic acid anions

Sulfenic acid anions represent an emerging nucleophile for the preparation of sulfoxides. Their S-functionalization chemistry can often be influenced by a nearby group that interacts with the component atoms of the sulfenate through non-bonding interactions. This study uses DFT methods to assess the importance of proximal boron-containing functional groups to direct S-alkylation chemistry of selected sulfenate anions. Several structural variations were modelled at the B3LYP/6-311++G(d,p) level, with the boron species positioned 3 to 5 carbons away from the alkylation site. Transition state free energies of S-alkylation transition states were located with and without sulfenate oxygen precomplexing to the nearby boron atom. The outcomes suggest that an ortho-substituted boronate ester on benzyl bromide can direct and accelerate an alkylation reaction principally due to a reduction of the entropic barrier. It was also determined that an intermolecular precomplex imparts too much stabilization to the sulfenate, thereby reducing its reactivity. The modelling suggests a possible aryl migration of the boronate/sulfenate complex is not competitive with S-alkylation.

Nickel phosphide nanoalloy catalyst for the selective deoxygenation of sulfoxides to sulfides under ambient H2 pressure

Exploring novel catalysis by less common, metal-non-metal nanoalloys is of great interest in organic synthesis. We herein report a titanium-dioxide-supported nickel phosphide nanoalloy (nano-Ni2P/TiO2) that exhibits high catalytic activity for the deoxygenation of sulfoxides. nano-Ni2P/TiO2 deoxygenated various sulfoxides to sulfides under 1 bar of H2, representing the first non-noble metal catalyst for sulfoxide deoxygenation under ambient H2 pressure. Spectroscopic analyses revealed that this high activity is due to cooperative catalysis by nano-Ni2P and TiO2.

Ni, Zn and Fe hydrotalcite-like catalysts for catalytic biomass compound into green biofuel

In this study, the deoxygenation pathway was proposed to eliminate oxygen species from biomass-derived oil, thereby producing a high quality of hydrocarbon chains (green fuel). The catalytic deoxygenation reaction of bio-oil model compound (oleic acid) successfully produced green gasoline (C8–C12) and diesel (C13–C20) via activated hydrotalcite-derived catalysts (i.e. CMgAl, CFeAl, CZnAl and CNiAl). The reaction was performed under inert N2 condition at 300 °C for 3 h, and the liquid products were analysed by GC–MS and GC–FID analyses to determine the hydrocarbon yield and product selectivity. The activity of the catalysts towards the deoxygenation reaction presented the following increasing order: CNiAl > CMgAl > CZnAl > CFeAl. CNiAl produced a hydrocarbon yield of up to 89 %. CNiAl demonstrated the highest selectivity with 83 % diesel production, whereas CMgAl showed the highest gasoline selectivity with 30 %. These results indicated that catalysts with a high acidic profile facilitate C–O cleavage via deoxygenation, producing hydrocarbons (mainly diesel-range hydrocarbons). Meanwhile, highly basic catalysts exhibit significant selectivity towards gasoline-range hydrocarbons via cracking and lead to the occurrence of C–C cleavage. The large surface area of CNiAl (117 m2 g−1) offered high approachability of the reactant with the catalyst’s active sites, thereby promoting high hydrocarbon yield. Consequently, the hydrocarbon yield and selectivity of the deoxygenation products were predominantly influenced by the acid–base properties and structural behaviour (porosity and surface area) of the catalyst.

Magnesium hydridotriphenylborate [Mg(thf)6][HBPh3]2: a versatile hydroboration catalyst

Magnesium bis(hydridotriphenylborate), isolated as a solvent-separated ion pair [Mg(thf)₆][HBPh₃]₂, effectively catalyzed the hydroboration of several unsaturated substrates including CO₂.

A practical and chemoselective Mo-catalysed sulfoxide reduction protocol using a 3-mercaptopropyl-functionalized silica gel (MPS)

3-Mercaptopropyl-functionalized silica gel (MPS) has been described as a new reducing agent for the chemoselective deoxygenation of sulfoxides under dioxomolybdenum(vi)-catalysis.

Main group catalysed reduction of unsaturated bonds

This Perspective article reviews the recent developments in reduction reactions catalysed by main-group element compounds.