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International audience; A heterogeneous catalyst consisting of bimetallic rhodium-ruthenium particles immobilized on carbon nanotubes was used in the hydroboration reaction and proved highly effective for a variety of alkenes and alkynes.

Two series of chlorine or fluorine derivatives containing monooxamato ligands result in diamagnetic complexes of Y3+ and La3+ and paramagnetic complexes of Nd3+ and Ho3+ that behave as single-ion magnets at lower temperatures.

This work reports a classification analysis method based on the vibrational Raman spectra of 38 quinones and related structures, spectrally ordering and classifying the compounds. The molecular systems are relevant for chemical and biological processes, with applications in pharmacology, toxicology and medicine. The classification strategy uses a combination of principal component analysis with K-means clustering methods. Both theoretical simulations and experimental data are analysed, thus establishing their spectral characteristics, as related to their chemical structures and properties. The protocol introduced here should be broadly applicable in other molecular and solid state systems.

Metal catalyzed C-H functionalization offers a versatile platform for methodology development and a wide variety of reactions now exist for the chemo- and site-selective functionalization of organic molecules. Cyclopentadienyl-metal (CpM) complexes of transition metals and their correlative analogues have found widespread application in this area, and herein we highlight several key applications of commonly used transition-metal Cp-type catalysts. In addition, an understanding of transition metal Cp-type catalyst synthesis is important, particularly where modifications to the catalyst structure are required for different applications, and a summary of this aspect is given.

A selective hydrazine sensor in solution based on the 2,1,3-benzothiadiazole heterocycle is efficient for in vitro and in vivo analyses. This sensor generates water as the only byproduct, avoiding generation of toxic compounds and interference during in vivo applications.

Over the past few decades, regioselective catalytic C-H functionalization has provided an attractive tool for unique retrosynthetic disconnections. The advancement of the directing group strategy in metal catalyzed synthetic transformation has contributed significantly to the incorporation of a wide range of functionalization reactions in both aromatic systems and aliphatic backbones. However, the extensive utilization of these methodologies depends on the ease of removal of the directing group to restore the free functional group. In this review, we have summarised the reported approaches for removing/modifying versatile directing groups.

Three new air-stable coordination compounds [Cu(HL)2(H2O)2]2·2H2O (1), [Cu(HL)2]n (1a), and [Zn(HL)2(H2O)2] (2), where HL = N-(4-hydroxyphenyl)oxamate, were successfully synthesized and characterized. Single-crystal X-ray analysis reveals 1 as a dinuclear copper(II) complex, in which the metal ions are connected through the carboxylate moieties of the oxamate ligands. The crystal structure of 1a is solved using powder X-ray diffraction data and stands for an anhydrous mononuclear copper(II) oxamate complex. 2 corresponds to the first example of a mononuclear Zn2+ oxamate complex containing both ligands and water solvent molecules in the cis arrangement. The presence of a phenol group in the oxamate ligand leads to different hydrogen bond patterns in the crystal packing in 1, 1a, and 2, resulting in supramolecular 3D architectures. Magnetic measurements of 1 reveal a ferromagnetic coupling between the copper(II) ions through the carboxylate–oxamate bridge [J = +0.829 cm−1, g = 2.101, zJ = +0.154 cm−1; H = −JSCu1·SCu2, where SCu1 = SCu2 = 1/2]. DFT calculations based on the broken symmetry formalism (DFT-BS) were performed to provide insight into the magnetic behavior.

Ortho-Quinones represent a special class of redox active compounds associated with a spectrum of pronounced biological activities, including selective cytotoxicity and antimicrobial actions. The modification of the quinone ring by simple nitrogen and sulphur substitutions leads to several new classes of compounds with their own, distinct redox behaviour and equally distinct activities against cancer cell lines and Trypanosoma cruzi. Some of the compounds investigated show activity against T. cruzi at concentrations of 24.3 and 65.6 μM with a selectivity index of around 1. These results demonstrate that simple chemical modifications on the ortho-quinone ring system, in particular, by heteroatoms such as nitrogen and sulphur, transform these simple redox molecules into powerful cytotoxic agents with considerable “potential”, not only in synthesis and electrochemistry, but also, in a broader sense, in health sciences.

International audience; A heterogeneous catalyst was assembled with ruthenium nanoparticles on carbon nanotubes and used in a mild oxidation method to prepare sulfones from sulfides. The system proved very efficient on the investigated substrates and the products were obtained in high yields.

Quinones are privileged chemical structures playing crucial roles as redox and alkylating agents in a wide range of processes in cells. The broad functional array of quinones has prompted the development of new chemical approaches, including C-H bond activation and asymmetric reactions, to generate probes for examining their activity by means of fluorescence imaging. This tutorial review covers recent advances in the design, synthesis and applications of quinone-based fluorescent agents for visualizing specific processes in multiple biological systems, from cells to tissues and complex organisms in vivo.

We report a sequential C–H iodination/organoyl-thiolation of naphthoquinones and their relevant trypanocidal activity. Under a combination of AgSR with a copper source, sulfur-substituted benzenoid quinones were prepared in high yields (generally >90%). This provides an efficient and general method for preparing A-ring modified naphthoquinoidal systems, recognized as a challenge in quinone chemistry.

Ruthenium-catalysis enabled the C-5 selective C-H oxygenation of naphthoquinones, and also sets the stage for the site-selective introduction of a hydroxyl group into anthraquinones. A-ring modified naphthoquinoidal compounds represent an important class of bioactive quinones for which the present study encompasses the first C-H oxygenation strategy by weak O-coordination.

Phenazinic ligands and Ru(II)-based complexes were synthesized from natural products lapachol and lawsone and evaluated against T. cruzi, the etiological agent of Chagas disease. These new ruthenium compounds could provide promising trypanocidal drugs. Besides synthesis and trypanocidal activity, this paper reports photophysical features and computational details of the compounds. The fluorescent trypanocidal substances are promising derivatives for further studies aiming to find molecules active against parasites associated with neglected diseases.

In this work, we characterize nor-β-lapachone-loaded (NβL-loaded) microcapsules prepared using an emulsification/solvent extraction technique. Features such as surface morphology, particle size distribution, zeta potential, optical absorption, Raman and Fourier transform infrared spectra, thermal analysis data, drug encapsulation efficiency, drug release kinetics and in vitro cytotoxicity were studied. Spherical microcapsules with a size of 1.03 ± 0.46 μm were produced with an encapsulation efficiency of approximately 19%. Quantum DFT calculations were also performed to estimate typical interaction energies between a single nor-β-lapachone molecule and the surface of the microparticles. The NβL-loaded PLGA microcapsules exhibited a pronounced initial burst release. After the in vitro treatment with NβL-loaded microcapsules, a clear phagocytosis of the spheres was observed in a few minutes. The cytotoxic activity against a set of cancer cell lines was investigated.

Quinonoid compounds based on 5-iodo-1,4-disubstituted-, 1,4- and 1,5-disubstituted-1,2,3-triazoles were synthesized using simple methodologies and evaluated against T. cruzi, the etiological agent of Chagas disease, and cancer cell lines PC3, HCT-116, HL-60, MDA-MB-435 and SF-295. The cytotoxic potential of the lapachones was also assayed against peripheral blood mononuclear cells (PBMC). Two compounds 6 and 12 were identified as potential hits against T. cruzi. β-Lapachone-based 1,5-disubstituted-1,2,3-triazole (12) displayed an IC50/24 h = 125.1 μM, similar to benznidazole, the standard drug. Compound 12 was also more active than the precursor β-lapachone against the cancer cell lines. These compounds acting as multitarget quinoidal systems could provide promising new leads for the development of trypanocidal and/or anticancer drugs.

This work describes a synthetic strategy for the syntheses of four new fluorescent excited state intramolecular proton transfer (ESIPT) prone oxazole derivatives synthesized from lapachol, a naturally occurring naphthoquinone isolated from the Tabebuia species (ipe tree). DFT calculations were performed to understand the ESIPT stabilizing process of these new derivatives. The new structures were designed to have improved lipophilic and balanced hydrophobic properties toward a selective cellular staining of lipid-based structures, that is, lipid inclusions in the cytosol. Cell-imaging experiments returned interesting results and showed the molecular architecture of the four derivatives had a great influence over the stabilizing processes in the excited state and over the selection of lipid inclusions inside the cells.

In our continued search for novel trypanocidal compounds, arylamine, chalcone, triazolic, triazole– carbohydrate and chalcogenium derivatives containing a naphthoquinone scaffold were prepared; in addition to electrochemical studies, these compounds were evaluated against the infective bloodstream form of Trypanosoma cruzi, the etiological agent of Chagas disease. Among the thirty-eight compounds herein evaluated, six were found to be more potent against trypomastigotes than the standard drug benznidazole, with IC50/24 h values between 52.9 and 89.5 mM.

Fluorescent naphthoxazoles and their boron derivatives have been synthesized and applied as superior and selective probes for endocytic pathway tracking in live cancer cells. The best fluorophores were compared with the commercially available acridine orange (co-staining experiments), showing far better selectivity.

The current manuscript describes the importance, mechanism propositions, evidence and controversies associated with multicomponent reactions (MCRs). The following multicomponent reactions are presented and critically evaluated: the Biginelli, Hantzsch, Mannich, Passerini and Ugi reactions. The aim of this review is to highlight what we already know about the mechanisms associated with these MCRs and the evidence supporting the proposed reaction pathways. Controversies and prospects are also discussed herein.

Cascade reactions of 1,3-dicarbonyls with Morita-Baylis-Hillman acetates of nitroalkenes using a quinine derived chiral squaramide organocatalyst led to the formation of pyranones and pyranonaphthoquinones in good to excellent yields and high diastereo-and enantioselectivities. Representative examples of the reaction scale-up with a much lower catalyst loading without an appreciable loss of selectivities and synthetic transformations of the products are also reported here. The compounds described herein for the first time were evaluated against the infective bloodstream form of Trypanosoma cruzi, the etiological agent of Chagas disease, since the structures are related to bioactive alpha-lapachones.

In this work, the electrochemical behaviour of an antitumoral nitro o-quinone derivative obtained from 3-bromo-nor-beta-lapachone was studied. Cyclic voltammetric experiments, in acetonitrile solution, revealed that both quinone and nitro functions are reduced independently as quasi-reversible one-electron transfer processes in this order. Depending on the reduction potential, a radical anion or a biradical dianion is obtained. The formation of these paramagnetic species was confirmed by performing in situ Electrochemical-Electron Spin Resonance (E-ESR) experiments. Analysis of the kinetics of electron transfer associated to those electron uptake processes, in terms of the Marcus-Hush-Levich model, revealed differences in the reorganization energy (lambda((k))) for both steps (lambda((I)): 1.07-1.11 eV; lambda((II)): 1.21-1.30 eV). By evaluating the conformations of the radical and biradical systems by calculations at the BLYP//TZVP level of theory, it was found that the inner component, for the second reduction process (lambda((II))) was approximately 72% of lambda((II)), reflecting modifications in the molecular structure during the radical anion-biradical dianion transition. This change is also reflected in the differences presented by line widths of the ESR signals of both electrogenerated radical and diradical species.