Antonio Monopoli

Heck reaction of β-substituted acrylates in ionic liquids catalyzed by a Pd-benzothiazole carbene complex

Abstract A Pd-catalyst with benzothiazole carbene as ligands allows, in tetrabutylammonium bromide melt as solvent, very fast and efficient reactions of haloaromatics with β-substituted acrylates.

Pd–benzothiazole carbene catalysed carbonylation of aryl halides in ionic liquids

Abstract The carbonylations of aryl halides with the Pd–carbene catalyst 1 were studied both in molecular solvents and in ionic liquids (ILs). Among the ILs, tetrabutylammonium bromide (TBAB) was found to give better results. Under these conditions the catalyst, when recovered and reused, did not show a significant decrease of activity. The role of TBAB on the catalyst stability is discussed.

Glucose as a Clean and Renewable Reductant in the Pd-Nanoparticle-Catalyzed Reductive Homocoupling of Bromo- and Chloroarenes in Water

An efficient and highly sustainable Ullmann-type homocoupling of bromo- and chloroarenes, including the more challenging electron-rich chloroarenes (e.g., 4-chloroanisole), catalyzed by in situ generated Pd colloids, is carried out in aqueous medium under relatively mild conditions (temperatures ranging from 40 to 90 degrees C). Glucose is used as a clean and renewable reductant, while tetrabutylammonium hydroxide (TBAOH) acts as base, surfactant, and phase-transfer agent, creating a favorable environment for the catalyst. Pd nanoparticle sizes, morphology, and chemical composition are ascertained by TEM and XPS analyses.

Palladium‐Nanoparticle‐Catalysed Ullmann Reactions in Ionic Liquids with Aldehydes as the Reductants: Scope and Mechanism

An efficient Ullmann-type reductive homocoupling of aryl, vinyl and heteroaryl halides can be promoted by an aldehyde in tetraalkylammonium ionic liquids under very mild reaction conditions. This simple procedure generates symmetrical biaryls under relatively mild conditions. The ionic liquid is crucial for this process because it behaves simultaneously as a base, ligand and reaction medium. The role of the aldehyde is also discussed and a general mechanism for this unusual reaction is proposed. These results open the way to a new efficient method of Pd-catalysed dehydrogenation of carbonyl compounds.

Proteomic Approach Based on MALDI-TOF MS To Detect Powdered Milk in Fresh Cow’s Milk

Milk and cheese are expensive foodstuffs, and their consumption is spread among the population because of their high nutritional value; for this reason they are often subjected to adulterations. Among the common illegal practices, the addition of powdered derivatives seems very difficult to detect because the adulterant materials have almost the same chemical composition of liquid milk. However, the high temperatures (180-200 °C) used for milk powder production could imply the occurrence of some protein modifications (e.g., glycation, lactosylation, oxidation, deamidation, dehydration). The modified proteins or peptides could then be used as markers for the presence of powdered milk. In this work, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was employed to analyze tryptic digests relevant to samples of raw liquid (without heat treatment), commercial liquid, and powdered cows milk. Samples were subjected to two-dimensional gel electrophoresis (2-DE); differences among liquid and powder milk were detected at this stage and eventually confirmed by MALDI analysis of the in gel digested proteins. Some diagnostic peptides of powdered milk, attributed to modified whey proteins and/or caseins, were identified. Then, a faster procedure was optimized, consisting of the separation of caseins from milk whey and the subsequent in-solution digestion of the two fractions, with the advantage of obtaining almost the same information in a limited amount of time. Finally, analyses were carried out with the fast procedure on liquid milk samples adulterated with powdered milk at different percentages, and diagnostic peptides were detected down to 1% of adulteration level.

Palladium/Zirconium Oxide Nanocomposite as a Highly Recyclable Catalyst for C-C Coupling Reactions in Water

Palladium nanoparticles have been electrochemically supported on zirconium oxide nanostructured powders and all the nanomaterials have been characterized by several analytical techniques. The Pd/ZrO2 nanocatalyst is demonstrated to be a very efficient catalyst in Heck, Ullmann, and Suzuki reactions of aryl halides in water. The catalyst efficiency is attributed to the stabilization of Pd nanophases provided by tetra(alkyl)-ammonium hydroxide, which behaves both as base and PTC (phase transfer catalyst) agent.

Analytical characterization of chitosan nanoparticles for peptide drug delivery applications.

Chitosan-cyclodextrin hybrid nanoparticles (NPs) were obtained by the ionic gelation process in the presence of glutathione (GSH), chosen as a model drug. NPs were characterized by means of transmission electron microscopy and zeta-potential measurements. Furthermore, a detailed X-ray photoelectron spectroscopy study was carried out in both conventional and depth-profile modes. The combination of controlled ion-erosion experiments and a scrupulous curve-fitting approach allowed for the first time the quantitative study of the GSH in-depth distribution in the NPs. NPs were proven to efficiently encapsulate GSH in their inner cores, thus showing promising perspectives as drug carriers.

Palladium‐Catalyzed Cross‐Coupling of Styrenes with Aryl Methyl Ketones in Ionic Liquids: Direct Access to Cyclopropanes

The combined use of Pd(OAc)2 , Cu(OAc)2 , and dioxygen in molten tetrabutylammonium acetate (TBAA) promotes an unusual cyclopropanation reaction between aryl methyl ketones and styrenes. The process is a dehydrogenative cyclizing coupling that involves a twofold CH activation at the α-position of the ketone. The substrate scope highlights the flexibility of the catalyst; a reaction mechanism is also proposed.

1,8-Bis(dimethylamino)naphthalene/9-aminoacridine: A new binary matrix for lipid fingerprinting of intact bacteria by matrix assisted laser desorption ionization mass spectrometry

The effectiveness of a novel binary matrix composed of 1,8-bis(dimethylamino)naphthalene (DMAN; proton sponge) and 9-aminoacridine (9AA) for the direct lipid analysis of whole bacterial cells by matrix assisted laser desorption ionization mass spectrometry (MALDI MS) is demonstrated. Deprotonated analyte signals nearly free of matrix-related ions were observed in negative ion mode. The effect of the most important factors (laser energy, pulse voltage, DMAN/9AA ratio, analyte/matrix ratio) was investigated using a Box-Behnken response surface design followed by multi-response optimization in order to simultaneously maximize signal-to-noise (S/N) ratio and resolution. The chemical surface composition of single or mixed matrices was explored by X-ray photoelectron spectroscopy (XPS). Moreover, XPS imaging was used to map the spatial distribution of a model phospholipid in single or binary matrices. The DMAN/9AA binary matrix was then successfully applied to the analysis of intact Gram positive (Lactobacillus sanfranciscensis) or Gram negative (Escherichia coli) microorganisms. About fifty major membrane components (free fatty acids, mono-, di- and tri-glycerides, phospholipids, glycolipids and cardiolipins) were quickly and easily detected over a mass range spanning from ca. 200 to ca. 1600 m/z. Moreover, mass spectra with improved S/N ratio (compared to single matrices), reduced chemical noise and no formation of matrix-clusters were invariably obtained demonstrating the potential of this binary matrix to improve sensitivity.

MALDI matrices for low molecular weight compounds: an endless story?

AbstractSince its introduction in the 1980s, matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) has gained a prominent role in the analysis of high molecular weight biomolecules such as proteins, peptides, oligonucleotides, and polysaccharides. Its application to low molecular weight compounds has remained for long time challenging due to the spectral interferences produced by conventional organic matrices in the low m/z window. To overcome this problem, specific sample preparation such as analyte/matrix derivatization, addition of dopants, or sophisticated deposition technique especially useful for imaging experiments, have been proposed. Alternative approaches based on second generation (rationally designed) organic matrices, ionic liquids, and inorganic matrices, including metallic nanoparticles, have been the object of intense and continuous research efforts. Definite evidences are now provided that MALDI MS represents a powerful and invaluable analytical tool also for small molecules, including their quantification, thus opening new, exciting applications in metabolomics and imaging mass spectrometry. This review is intended to offer a concise critical overview of the most recent achievements about MALDI matrices capable of specifically address the challenging issue of small molecules analysis. Graphical abstractAn ideal Book of matrices for MALDI MS of small molecules