Susana Porcel

Strategic electronic matching between imidazolium precursors and aryldiazonium salts enables the synthesis of azoimidazolium derivatives via an operationally simple, base‐promoted protocol that circumvents the need for column chromatography. The resulting azoimidazolium scaffolds serve as precursors of highly persistent neutral aminyl radicals, which exhibit remarkable stability with negligible decay after 3 weeks in the solid state. Furthermore, these salts were successfully employed as a versatile platform to access novel Au(I)‐mesoionic carbene (MIC) complexes. When evaluated in living human glioblastoma A172 cells, these Au(I)–MIC acted as efficient, cell‐permeable fluorophores with an unprecedented substituent‐governed, dual‐channel readout spanning from the green to the red region, governed by donor strength of the peripheral substituents.

This work describes the synthesis of methyl orange and fluorescein and their applications in canvas painting. By modulation of the pH and concentration of methyl orange, a range of yellow, orange, and reddish hues can be obtained, illustrating its pH-dependent chromatic behavior. In contrast, fluorescein contributes fluorescence-based effects: due to its tendency to form aggregates at higher concentrations, the fluorescence intensity of fluorescein-based paint depends strongly on concentration, with differences becoming clearly observable upon exposure to UV light. By integration of concepts from organic chemistry and art, this approach provides a multidisciplinary, hands-on learning experience that connects fundamental chemistry principles with artistic expression through experimentation.

The synergistic action of ascorbic acid and NHC^N ligands enables the challenging oxidation of Au(I) with electron‐rich aryldiazonium salts in the absence of a cocatalyst and/or irradiation. EPR, NMR, and x‐ray analyses reveal the reaction to be triggered by a radical pathway facilitated by the ligand‐assisted stabilization of the Au(III) center. The utility of this synergistic effect was demonstrated in a catalytic arylative carbocyclization, providing access to a 3,4‐diaryl‐2 H ‐chromene containing two electron‐rich aryl groups, a substitution pattern inaccessible by previous protocols.

En los últimos años han emergido varias estrategias que facilitan la oxidación de catalizadores homogéneos de Au(I), permitiendo la exploración del potencial sintético asociado a ciclos rédox Au(I)/Au(III). En este contexto, nuestro grupo de investigación ha participado en el desarrollo de metodologías que posibilitan la creación de enlaces C(S)-arilo, empleando sales de arildiazonio como electrófilos. El presente artículo resume el estado del arte de la investigación en esta área y nuestra contribución al respecto. Además, muestra un tipo de reactividad menos explorada, en la que las sales de arildiazonio conservan el grupo diazo, lo que conduce a la formación de heterociclos nitrogenados.

This study shows that aryldiazonium salts can participate as electrophiles in gold‐catalyzed C–H arylation of arenes. Using 2‐diazo benzophenones, a gold‐catalyzed oxidation/C–H activation/cyclization sequence has been developed, leading to valuable fluorenones. Key parameters for the reaction to proceed in good yields are the introduction of electron‐donating groups, the use of PF₆⁻ as counteranion, and terpyridine as an auxiliary ligand.

We describe herein a gold-catalyzed three-component reaction of o-alkynylbenzaldehydes, aryldiazonium salts, and trimethoxybenzene. This process enables the one-pot formation of valuable isoindoles and 1,2-dihydrophathalazines. The regioselectivity of the reaction is dictated by the nature of the aryldiazonium salt. Noticeably, the reaction is performed at room temperature under mild conditions and tolerates a variety of functional groups on both the o-alkynylbenzaldehyde and the aryldiazonium salt. Experimental mechanistic studies suggest that it is catalyzed by arylAu(III) species.

A one‐pot diazotization/gold‐mediated cyclization of 2‐aminoaryl‐3‐arylpropargyl‐benzenesulfonamides is described. After diazotization, Me₂SAuCl triggers an oxy‐ and/or chloroarylation of the alkyne moiety, resulting in the formation of 3‐acylindoles and/or Z‐3‐(chloromethylene)indolines. Density Functional Theory (DFT) calculations show the significant energetic preference of both processes over an insertion pathway. Notably, a Z‐3‐(chloromethylene)indoline crystallized with [Cl‐Au‐Cl],⁻ exhibiting Au⋅⋅⋅H−C short contacts.

In this work, the coupling of aryldiazonium salts with thiols mediated by the readily accessible gold complex Me₂SAuCl is described. In the reported protocol, the addition of 2,2′‐bipyridine as a ligand leads to higher yields than phosphines. The reaction proceeds at room temperature under soft mildconditions and has a broad scope in both the aryldiazonium salt and the thiol. Notably, the coupling works with aryldiazonium salts containing two additional substituents.

A gold-catalysed coupling of aryldiazonium salts with arylboronic acids is described. The reactions proceed in satisfactory yields under irradiation with blue LEDs in the presence of KF and a catalytic amount of ascorbic acid. Notably, 4-nitrobenzendiazonium tetrafluoro­borate is sufficiently reactive to undergo the coupling with a variety of arylboronic acids in the absence of aryl radical initiators. The coupling is applicable for electron-donating and electron-withdrawing groups present at the para, ortho, and meta positions of both substrates.