Microwave Assisted Esterification of Aryl/Alkyl Acids Catalyzed by N-Fluorobenzenesulfonimide

The susceptibility of the carbonyl group towards nucleophilic attack affords the construction of various organic compounds. Thus, investigations of carbonyl activation applying greener methodologies are highly important. In the present work, among the investigated N-halo compounds, N-fluorobenzenesulfonimide (NFSi) has been found as an efficient and selective catalyst in the reaction of direct esterification of aryl and alkyl carboxylic acids supported by microwave (MW) irradiation. The comprehensive esterification of different benzoic acids and mono-, di-and tri-carboxy alkyl derivatives was performed, whereby significant reaction time reductions were achieved. The presented method used NFSi as an easily manipulatable, non-metal, water-and air-tolerant catalyst, allowing simple synthetic and isolation procedures and energy saving, compared to conventional methodologies. Importantly, in contrast to esterification under thermal conditions, where N-halo compounds behave as pre-catalysts, in the MW-supported protocol, a distinct reaction mechanism has been proposed that assumes NFSi as a sustainable catalyst. Moreover, a scale-up of the industrially important derivative was performed

A Mass Spectral Study of Substituent Effects in Some Substituted N,N-Dimethyl-N\u27-Phenyl- and N\u27-Pyridyl-Formamidines

Several competing fragmentation reactions, initiating directly from the molecular ion, which are common to p- and m- substituted N,N-dimethyl-N\u27- phenyl-formamidine, were examined. IP, AP and daughter/parent ion ratio measurements were made to provide some insight into the substituent effects on reaction mechanisms. The results obtained were compared with those found for the compounds N,N-dimethyl-N\u27-pyridyl-4-formamidine and isomeric 3-formamidine. The substituent constant o/ for the nitrogen in the pyridine ring was determined

The Chemistry of Organo Halogenic Molecules. 155. The Role of Reagent Structure in Halogenation of 9-Substituted Phenanthrenes

9-Substituted phenanthrenes were used as target molecules in investigations of the effect of the reagent structure and reaction conditions on halogenation with bromine (1), CsSO4F (2) and F-TEDA (1-chloromethyl-4-fluoro-1,4-diazoniabicycloe[2,2,2]octane bis(tetra- fluoroborate), (3). 9-Methoxyphenanthrene (4) was converted to 9- bromo-10-methoxyphenanthrene (6a) and 9-bromo-10-hydroxy- phenanthrene (7a), while the amount of dealkylation depended on the solvent and was more pronounced in methanol than in acetonitrile, but no adduct was observed. Addition reaction became a major process in fluorination with CsS04F (2) in methanol and 88% of 9-fluoro-10,10-dimethoxy-9,10-dihydrophenanthrene (8b) was formed, while dealkylation occurred in acetonitrile. The course of fluorination of 9-methoxyphenanthrene with F-TEDA (3) could be completely manipulated by the choice of solvent and 9,9-difluoro- 10-oxo-9,10-dihydrophenanthrene (9b) was formed in acetonitrile, 9-fluoro-10-methoxyphenanthrene (6b) in trifluoroacetic acid and 9-fluoro-10,10-dimethoxy-9,10-dihydrophenanthrene (8b) in methanol. Bromination of 9-hydroxyphenanthrene (5) in acetonitrile resulted only in the substitution process, while 9-fluoro-10-hydroxyphenanthrene (7b) formed in the reaction with CsSO4F and F-TEDA was more reactive than the starting hydroxy derivative and, using a 2 molar ratio of F-TEDA, only 9,9-difluoro-10-oxo- 9,10-dihydrophenanthrene (9b) was formed

Abiotic formation of methyl iodide on synthetic birnessite: A mechanistic study

Methyl iodide is a well-known volatile halogenated organic compound that contributes to the iodine content in the troposphere, potentially resulting in damage to the ozone layer. Most methyl iodide sources derive from biological activity in oceans and soils with very few abiotic mechanisms proposed in the literature. In this study we report that synthetic manganese oxide (birnessite δ-MnO2) can catalyze the formation of methyl iodide in the presence of natural organic matter (NOM) and iodide. Methyl iodide formation was only observed at acidic pH (4–5) where iodide is oxidized to iodine and NOM is adsorbed on δ-MnO2. The effect of δ-MnO2, iodide and NOM concentrations, nature of NOM and ionic strength was investigated. High concentrations of methyl iodide were formed in experiments conducted with the model compound pyruvate. The Lewis acid property of δ-MnO2 leads to a polarization of the iodine molecule, and catalyzes the reaction with natural organic matter. As manganese oxides are strong oxidants and are ubiquitous in the environment, this mechanism could significantly contribute to the global atmospheric input of iodine

Local Piezoelectric Behavior of Potassium Sodium Niobate Prepared by a Facile Synthesis via Water Soluble Precursors

Due to the ever-increasing restrictions connected to the use of toxic lead-based materials, the developing of lead-free piezoceramics has become one of the most urgent tasks. In this context, potassium sodium niobate materials (KNN) have attracted a lot of interest as promising candidates due to their excellent piezo properties. For this reason, many efforts have been addressed to optimize the synthesis process now suffering by several drawbacks including the high volatilization of potassium and sodium at the conventional high temperature treatments and the use of expensive metal precursors. To overcome these issues, a new modified Pechini method to synthesize single phase KNaNbO powders, from water soluble metal precursors, is presented. Microstructural and structural parameters are characterized by X-ray diffraction (XRD). Depending on the amount of citric acid added to the starting reagents, two pure single-phase KNaNbO (2 g citric acid) and KNaNbO (0.2 g citric acid), respectively, are obtained with a good crystallinity at a moderate temperature of 500 °C. The piezo responses of the as calcined systems are tested by piezoresponse force microscopy (PFM). KNaNbO exhibits a much higher response with respect to the other phase, which relates to the larger crystallinity and to the chemical composition

Switchable synthesis of Z-homoallylic boronates and E-allylic boronates by enantioselective copper-catalyzed 1,6-boration

The enantioselective Cu-catalyzed 1,6-boration of (E,E) α,β,γ,δ-unsaturated ketones is described, which gives homoallylic boronates with high enantiomeric purity and unexpectedly high Zselectivity. By changing the solvent, the outcome can be altered to give E-allylic boronates