A Chemoselective Hydrogenation of the Olefinic Bond of α,β-Unsaturated Carbonyl Compounds in Aqueous Medium under Microwave Irradiation

Transition Metal-Catalyzed Transformations of Chalcones

Chalcones are a class of naturally occurring flavonoid compounds associated to a variety of biological and pharmacological properties. Several reviews have been published describing the synthesis and biological properties of a vast array of analogues. However, overviews on the reactivity of chalcones has only been explored in a few accounts. To fill this gap, a systematic survey on the most recent developments in the transition metal-catalyzed transformation of chalcones was performed. The chemistry of copper, palladium, zinc, iron, manganese, nickel, ruthenium, cobalt, rhodium, iridium, silver, indium, gold, titanium, platinum, among others, as versatile catalysts will be highlighted, covering the literature from year 2000 to 2023, in more than 380 publications.

Highly efficient iron-catalyzed conjugate reduction of α,β-unsaturated ketones with polymethylhydrosiloxane

An iron-catalyzed ligand free conjugate reduction of α,β-unsaturated ketones with PMHS (polymethylhydrosiloxane) was reported to deliver the corresponding carbonyl compounds with up to 93% yield. This operationally simple protocol shows a broad substrate scope using readily available PMHS as a cost-effective and easy-to-handle reductive reagent.

Direct conversion of secondary propargyl alcohols into 1,3-di-arylpropanone via DBU promoted redox isomerization and palladium assisted chemoselective hydrogenation in a single pot operation

Palladium(ii)acetate is found to be an efficient catalyst for the single-step conversion of secondary propargyl alcohols to 1,3-diarylpropanone derivatives under mild basic conditions.

Cascade cyclization versus chemoselective reduction: a solvent-controlled product divergence

A convenient controllable cascade cyclization and partial reduction of enones for the divergent construction of two types of valuable compounds including polysubstituted thiophenes and saturated ketones are developed.

Pd(ii)/Zn co-catalyzed chemo-selective hydrogenation of α-methylene-γ-keto carboxylic acids

Divergent synthesis of α-methyl-γ-keto carboxylic acids, α-methylcarboxylic acids, and lactones from α-methylene-γ-keto carboxylic acids.

Transition-Metal-Free Highly Chemoselective and Stereoselective Reduction with Se/DMF/H2O System

A novel metal-free reduction system, in which H₂Se (or HSe^-) produced in situ from Se/DMF/H₂O acts as the active reducing species, has been developed. By using water as an inexpensive, safe, and environmentally friendly surrogate as the hydrogen donor, this new reduction system incorporating Se/DMF/H₂O displayed high selectivity and good activity in the reduction of α,β-unsaturated ketones and alkynes. Therefore, this reduction system has great potential to be a general and practical reduction methodology in organic transformation.

Microwaves in the Catalytic Valorisation of Biomass Derivatives

The application of microwave irradiation in the transformation of biomass has been receiving particular interest in recent years due to the use of polar media in such processes and it is now well-known that for biomass conversion, and particularly for lignocellulose hydrolysis, microwave irradiation can dramatically increase reaction rates with no negative consequences on product selectivity. However, it is only in the last ten years that the utilisation of microwaves has been coupled with catalysis aiming towards valorising biomass components or their derivatives via a range of reactions where high selectivity is required in addition to enhanced conversions. The reduced reaction times and superior yields are particularly attractive as they might facilitate the transition towards flow reactors and intensified production. As a consequence, several reports now describe the catalytic transformation of biomass derivatives via hydrogenation, oxidation, dehydration, esterification and transesterification using microwaves. Clearly, this technology has a huge potential for biomass conversion towards chemicals and fuels and will be an important tool within the biorefinery toolkit. The aim of this chapter is to give the reader an overview of the exciting scientific work carried out to date where microwave reactors and catalysis are combined in the transformation of biomass and its derivatives to higher value molecules and products.

Chemoselective catalytic reduction of conjugated α,β-unsaturated ketones to saturated ketones via a hydroboration/protodeboronation strategy

A novel copper-catalyzed chemoselective reduction of a carbon–carbon double or triple bond to a carbon–carbon single bond on α,β-unsaturated ketones is developed, this reaction proceeds under hydrogen gas or stoichiometric metal hydride free conditions.

An efficient ligand free chemoselective transfer hydrogenation of olefinic bonds by palladium nanoparticles in an aqueous reaction medium

An efficient ligand free catalytic system was developed for chemoselective 1,4-reduction of various α,β-unsaturated carbonyls by palladium nanoparticles in aqueous reaction medium with excellent chemoselectivity and effective catalyst recyclability.

A practical approach for ambient-pressure hydrogenations using Pd on porous glass

A Pd on porous glass catalyst system was used in the liquid-phase hydrogenation of terpenoid substrates with dihydrogen at room temperature and atmospheric pressure. A multitude of substances were hydrogenated selectively with yields of 90-100 %. In all experiments, only C--C, C--N, and N--N double bonds were hydrogenated. Studies revealed that carbonyl and aromatic double bonds are inert towards catalytic reduction with dihydrogen under the conditions employed. In some cases, hydrogenation was accompanied by isomerization, so that treatment of beta-pinene, for example, afforded isomeric alpha-pinene, which was subsequently hydrogenated to pinane.