Francisco Javier Arnáiz

A novel domino reduction/imine formation/intramolecular cyclization/oxidation for the efficient synthesis of pyrrolo(indolo)[1,2-a]quinoxalines and pyrrolo(indolo)[3,2-c]-quinolines from readily available nitrobenzenes and glycols is reported. The process utilizes the carbonyl byproduct of the initial dioxomolybdenum(VI)-catalyzed reduction of nitroaromatics with glycols as a reagent for the imine generation. This method represents the first sustainable domino reaction for the preparation of biologically relevant heterocycles that internally incorporates the waste formed in the first step to the final product.

A molybdenum‐catalyzed deoxygenation of pyridine N‐oxides and N‐hydroxybenzotriazoles, as well as other azole N‐oxides, has been developed using pinacol as an environmentally friendly oxo‐acceptor. The only by‐products are acetone and water making the process a convenient alternative to established protocols in terms of waste generation. The reaction is highly chemoselective and a variety of functional groups are tolerated. The processes are usually very clean allowing the isolation of the pure deoxygenated products after a simple extraction in most cases. magnified image

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

An efficient and eco-friendly oxidative cleavage of glycols using DMSO as an oxidant catalyzed by dioxomolybdenum( vi ) complexes has been developed.

This work provides structural evidence for different desulfurization processes in aqueous solutions of [CuL]⁺ derivatives (HL = pyridine-2-carbaldehyde thiosemicarbazone). Structural resolution has been achieved for the [{CuL(SH)}₂] (1), [CuLCl]₂[Cu(pic)₂] (pic⁻ = picolinato, pyridine-2-carboxilato) (2) and [Cu(HL)(NCS)](NO₃) (4) compounds, together with a derivative of 4 with formula [Cu(HL)(NCS)][Cu(HL)(NCS)_0.72(NO₃)_0.28](NO₃)₂ (5), whose HS⁻, pic⁻ and NCS⁻ ligands come from thiosemicarbazone breakage. The behaviour of the [CuL]⁺ species in basic aqueous solutions or water under reflux has been compared with that exhibited by iron(III), cobalt(III), zinc(II) and lead(II) derivatives of the same thiosemicarbazone ligand. [Cu(L′)]⁺ species (HL′ = pyridine-2-carbaldehyde N4-methylthiosemicarbazone) have also been analyzed by infrared spectroscopy or mass spectrometry under the same experimental conditions. In addition, preparative methods for a rational synthesis of the serendipitously obtained compounds are proposed. In this way, the crystal structure of [CuL(pic)]·3H₂O (3) has been elucidated too. The partial desulfurization of coordinated thiosemicarbazones could lead to a reinterpretation of their biological activity with consequences for the search for possible therapeutic uses.

A new application for glycerol that expands its possibilities beyond a green solvent and a precursor of value-added products has been demonstrated. Simple, easily available, and environmentally friendly dioxomolybdenum(VI) complexes are highly efficient catalysts for the chemoselective sulfoxide deoxygenation with this biomass-derived chemical feedstock. Both refined glycerol and crude glycerin can be used, thus expanding the potential application of this reaction. Subsequent transformation of glycerol during this reductive process has also been investigated.

Pinacol is disclosed as a new chemoselective and environmentally benign reducing agent for sulfoxides and nitroaromatics assisted by readily available dichlorodioxomolybdenum(VI) complexes as catalysts. A wide range of substrates including those bearing challenging functional groups has been efficiently and selectively reduced with acetone and water being the only by‐products of these reactions.