Marc Montesinos-Magraner

The decarboxylative borylation of redox‐active esters promoted by bis(catecholato)diboron (B ₂ cat ₂ ) and blue light enables the synthesis of versatile organoboron building blocks from carboxylic acid materials. An LED‐illuminated NMR kinetic study revealed that the reaction is surprisingly accelerated by water, and this hidden catalysis can be attributed to a novel intermediate formed in situ, namely a hypoboric acid catecholate (HAC). This unsymmetrical diboron species can alternatively be formed by hydrolysis of B ₂ cat ₂ or transesterification between B ₂ cat ₂ and hypoboric acid (B ₂ (OH) ₄ ). Experimental and computational studies revealed and rationalized the regioselective capture of alkyl radicals by the HAC species, and the concomitant formation of a more reductive boryl radical chain carrier. The regioselectivity is characteristic of the HAC species studied, and is controlled by electronic rather than steric effects.

The utility of underexplored vinylogous isocyano esters in the synthesis of oxazole derivatives is demonstrated herein. A divergent base-promoted tandem (3+2) cyclization–isomerization reaction with aldehydes divergently yields bisubstituted oxazoles (up to 90% in MeOH with 2 equiv of DBU) or oxazolines (up to 80% in CH2Cl2 with 1 equiv of DBU) A density functional theory (DFT) study of these reactions supports the experimental evidence, confirming the mechanism and selectivity of this divergent process.

An enantioselective strategy for the synthesis of chiral 3-alkyl-1,5-functionalized 1,4-diynes is reported. The method involves a highly enantioselective organocatalytic conjugate addition of isoxazol-5(4H)-ones to nitroenynes followed by a Zard-type transformation under one-pot conditions yielding chiral skipped diynes in good overall yields and with excellent enantioselectivities. This study highlights the synthetic versatility of the isoxazol-5(4H)-one scaffold and its value as a platform for accessing structurally diverse and synthetically relevant building blocks.

Las asignaturas experimentales, como los laboratorios de química orgánica en el Grado en Química, son a menudo difíciles de evaluar de manera objetiva e individualizada. En esta comunicación se presenta el proyecto de innovación educativa UV-SFPIE_PIEE-3328892, desarrollado en la Universitat de València, cuyo objetivo ha sido mejorar la evaluación y superar las limitaciones existentes en las asignaturas de Laboratorio de Química Orgánica I y II del Grado en Química. Para ello, se han diseñado rúbricas de evaluación que buscan garantizar una valoración objetiva, coherente y uniforme por parte del profesorado. Estas rúbricas están orientadas a facilitar la evaluación formativa de las prácticas, teniendo en cuenta la adquisición de competencias por parte del alumnado. Posteriormente, las rúbricas se implementaron en grupos reducidos de estas asignaturas experimentales, y se realizaron encuestas de valoración entre los estudiantes participantes, con el fin de evaluar la efectividad de las rúbricas e identificar posibles áreas de mejora.

In this communication, a straighforward asymmetric synthesis of spiro‐indoline‐pyrazolone compounds is described. This methodology consists in a formal [4+1] cycloaddition reaction of 4‐bromopyrazolones and aza‐ortho‐quinone methides generated in situ catalyzed by a bisquinine‐derived squaramide in CHCl₃ under basic conditions. A variety of chiral spirocyclic compounds bearing a pyrazolone and an indoline moieties were obtained in moderate to good yields (up to 68 %) and moderate to excellent enantioselectivities (up to 93 % ee).

A new generation of chiral gold(I) catalysts based on variations of complexes with JohnPhos-type ligands with a remote C₂-symmetric 2,5-diarylpyrrolidine have been synthesized with different substitutions at the top and bottom aryl rings: from replacing the phosphine by a N-heterocyclic carbene (NHC) to increasing the steric hindrance with bis- or tris-biphenylphosphine scaffolds, or by directly attaching the C₂-chiral pyrrolidine in the ortho-position of the dialkylphenyl phosphine. The new chiral gold(I) catalysts have been tested in the intramolecular [4+2] cycloaddition of arylalkynes with alkenes and in the atroposelective synthesis of 2-arylindoles. Interestingly, simpler catalysts with the C₂-chiral pyrrolidine in the ortho-position of the dialkylphenyl phosphine led to the formation of opposite enantiomers. The chiral binding pockets of the new catalysts have been analyzed by DFT calculations. As revealed by non-covalent interaction plots, attractive non-covalent interactions between substrates and catalysts direct specific enantioselective folding. Furthermore, we have introduced the open-source tool NEST, specifically designed to account for steric effects in cylindrical-shaped complexes, which allows predicting experimental enantioselectivities in our systems.

Chiral difluorinated tertiary alcohols are obtained in moderate to excellent yields and high enantioselectivities upon a Cu( ii )-catalysed reaction of difluorinated silyl enol ethers and acylpyridine N -oxides.

H‐bonded counterion‐directed catalysis (HCDC) is a strategy wherein a chiral anion that is hydrogen‐bonded to the achiral ligand of a metal complex is responsible for enantioinduction. In this article we present the application of H‐bonded counterion‐directed catalysis to the Au(I)‐catalyzed enantioselective tandem cycloisomerization‐addition reaction of 2‐alkynyl enones. Following the addition of C‐, N‐ or O‐centered nucleophiles, bicyclic furans were obtained in moderate to excellent yield and enantioselectivity (28 examples, 59–96 % yield, 62 : 38 to 95 : 5 er). The optimal catalytic system, comprising a phosphinosquaramide Au(I) chloride complex and a BINOL‐derived phosphoramidate Ag(I) salt, was selected in a combinatorial fashion from a larger library with the help of high‐throughput screening. An enantioselectivity switch of ca. 120 Δee% was observed upon addition of the achiral Au(I) component to the Ag(I) salt.