Carlos Arróniz

A two-catalyst system comprising different oxidation states of palladium is described, which mediates the isomerization of alkynyl epoxides to furans. In a process termed 'dual oxidation state tandem catalysis', a multistep isomerization pathway is delineated in which the different metal oxidation states and ligands play independent mechanistic roles, but which in combination enable the use of milder reaction conditions and lower catalyst loadings than a single catalyst in isolation. In the present context, this rare example of a homobimetallic catalytic transformation provides a mild, scalable and atom-efficient route for furan synthesis.

A wide range of halogenated bicyclo[1.1.1]pentanes are accessed by functional group tolerant radical ring-opening of tricyclo[1.1.1.0^1,3]pentane, using triethylborane as initiator.

A general, cost-effective and sustainable replacement for silver in palladium catalysed direct arylations of C(sp²)–H and C(sp³)–H bonds.

ortho-Arylation of ortho-substituted benzoic acids is a challenging process due to the tendency of the reaction products toward Pd-catalyzed protodecarboxylation. A simple method for preventing decarboxylation in sterically hindered benzoic acids is reported. The method described represents a reliable and broadly applicable entry to 2-aryl-6-substituted benzoic acids.

Bicyclic α-iminophosphonates were prepared via the first diastereoselective silver catalyzed [3 + 2] cycloaddition reaction of diethyl isocyanomethylphosphonate and diversely N-substituted maleimides. The reduction of the resulting imine by catalytic hydrogenation led to cyclic α-aminophosphonates, which are α-aminoester surrogates. The relative stereochemistry of the adducts was confirmed by X-ray crystallographic analysis of 4. The diastereoselectivity of the cycloaddition reaction was rationalised by theoretical studies.

A cooperative multicatalytic cascade sequence involving isocyanoacetates and α,β‐unsaturated ketones is described for the enantioselective synthesis of 2,3‐dihydropyrroles. The key to promoting the multistep asymmetric reaction is the combination of cinchona alkaloid derived organocatalysts with silver nitrate. Merging both organic and metal catalytic cycles enables the formation of two C–C bonds and the generation of a stereogenic center in a single process. The study has also shown that the bifunctional role of the organocatalyst is crucial for the asymmetric version of the cycloaddition reaction.

Readily available chiral primary 1,2-aminoalcohols and diamines have been explored as organocatalysts for a domino Michael–aldol reaction. Their application in this organocascade process afforded cyclohexanone A with high levels of reactivity (up to 91% yield) and stereoselectivity (>97 : 3 d.r., up to 93% ee). Depending on the acid cocatalyst different chiral species (cyclic secondary aminesvs. acyclic primary amines) might catalyse the process. In order to shed light on the catalytic activation, several experiments were carried out and a detailed possible reaction mechanism is proposed. Theoretical studies support the stereochemical outcome of the process.

The double cyclocondensation of symmetric pyridyl bis(oxoacids) 2b and 3b with (R)-phenylglycinol stereoselectively gave access to bis-phenylglycinol-derived oxazolopyrrolidine 9 and oxazolopiperidone 10, respectively. Application of the stereocontrolled cyclocondensation reaction to phenyl bis-γ-oxoacid 4b provided 11, which was converted to the corresponding enantiopure di(pyrrolidinyl)benzene 22. The absolute configuration of the new stereogenic centers generated in the key cyclocondenstion step was unambiguously established by X-ray crystallographic analysis.