Novel and Cleaner Synthesis of Pyridinium Salts from Pyridoxal Oxime and Substituted Phenacyl Bromides

An efficient green synthesis of quaternary pyridinium salts by liquid-assisted grinding (LAG) is reported. A series of reactions of pyridoxal oxime with substituted phenacyl bromides was carried out in a mortar and pestle. This new and cleaner method provides several advantages such as being environmentally friendly, using a simple workup procedure, and affording moderate to excellent yields. All products were deduced from their IR, NMR spectroscopic and elemental analysis data. (doi: 10.5562/cca2364

An Efficient Synthesis of Pyridoxal Oxime Derivatives under Microwave Irradiation

Quaternary salts of pyridoxal oxime have been synthesized by the quaternization of pyridoxal oxime with substituted phenacyl bromides using microwave heating. Microwave-assisted rapid synthesis was done both in solvent (acetone) and under solvent-free conditions. Good to excellent yields (58%94%) were obtained in acetone in very short reaction times (35 min) as well as in the solvent-free procedure (42%78%) in very short reaction times (710 min) too. Effective metodologies for the preparation of pyridoxal oxime quaternary salts, having the advantagies of being eco-friendly, easy to handle, and performed in shorter reactions time are presented. The structure of compound 7, in which a 4-fluorophenacyl moiety is bonded to the pyridinium ring nitrogen atom, was unequivocally confirmed by the single-crystal X-ray diffraction method

Occurence of pharmaceuticals in surface water

Pharmaceuticals constitute a large group of human and veterinary medicinal organic compounds which have long been used throughout the world. According to their therapeutic activity they are classified in several groups: antibiotics, analgesics/antipyretic, CNS (Central nervous system) drugs, cardiovascular drugs, endocrinology treatments, diagnostic aid-adsorbable organic halogen compounds. Pharmaceuticals are designed to have a physiological effect on humans and animals in trace concentrations. Pharmaceuticals end up in soil, surface waters and eventually in ground water, which can be used as a source of drinking water, after their excretion (in unmetabolized form or as active metabolites) from humans or animals via urine or faeces. The possible fates of pharmaceuticals once they get into the aquatic environment are mainly three: (i) ultimately they are mineralized to carbon dioxide and water, (ii) the compound does not degrade readily because it is lipophilic and is partially retained in the sedimentation sludge and (iii) the compound metabolizes to a more hydrophilic molecule, passes through the wastewater treatment plant and ends up in receiving waters (which are surface waters, mainly rivers). These compounds exhibit the highest persistence in the environment. In recent years, and in particular after the use of the advanced measurement technologies, many pharmaceuticals have been identified worldwide and detected at ng/L levels (trace concentrations) in the aquatic environment, and are considered as an emerging environmental problem due to their continuous input and persistence in the aquatic ecosystem even at low concentrations

Biocatalytic reductions by plant tissue - Green alternative to alcohol production

The use of biocatalysts for the industrial synthesis of chemicals has been attracting much attention as an environmental friendly synthetic method. Various plants, such as apple (Malus pumila), carrot (Daucus carota), cucumber (Cucumis sativus), onion (Allium cepa), potato (Solanum tuberosum), radish (Raphanus sativus) and sweet potato (Ipomoea batatas) were used as biocatalysts. Enzymes that plants produce are able to perform reactions under mild conditions (pH and temperature), with remarkable chemo-, regio-, and stereoselectivity. Due to this feature the number of biocatalysts used in organic synthesis has rapidly increased during the last decades, especially for the production of chiral compounds. This review presents biotechnological processes for the production of chiral alcohols by reducing prochiral ketones with whole plant tissue. Chiral alcohols are important building blocks for the synthesis of pharmaceuticals, pesticides, pheromones, flavors, fragrances and advanced materials such as liquid crystals. Reductase-catalyzed reactions are dependent on cofactors, and therefore, one major task in process development is to provide an effective method for regeneration of the cofactors consumed. The need for expensive cofactors is eliminated by using the whole plant tissue since the plant automatically provides this requirement. Depending on the vegetable used, either enantiomer may be obtained in high yield and high enantiomeric excess (ee), which could be a critical factor for drug development/bioactivity evaluation perspective. In this paper, various processes carried out on laboratory scales are presented. Attention is turned to conversion, yield, enantiomeric excess (ee)

Novel Synthetic Routes to Quaternary Pyridinium Salts and their Antifungal Activity

Eleven pyridine derivatives were prepared by quaternization reactions by different synthetic routes: conventional, microwave, and ultrasound. Since acetone and other solvents used in conventional quaternization reactions are harmful, attempts were made to replace the organic solvents with more environmentally friendly alternative - deep eutectic solvents. The reactions were carried out using pyridine-3-aldoxime, pyridine-4-aldoxime, isonicotinamide and nicotinamide as nucleophiles and three different dihaloalkanes as electrophiles: diiodopro¬pane, dibromopropane and diiodohexane. The results showed that the microwave method using acetone as solvent was significantly faster and gave higher yields than the conventional method. In contrast, synthesis in the eutectic solvents choline chloride : urea gave significantly lower yields. The structures of the synthesized compounds were confirmed by 1H and 13C NMR spectroscopy, mass spectrometry and elemental analysis. The antifungal activity of all compounds was tested at two different concentrations (10 and 100 µg mL–1) against Botrytis cinerea, Fusarium culmorum, Macrophomina phaseolina and Sclerotinia sclerotiorum in vitro. All tested compounds showed excellent inhibitory activity against the studied phytopathogenic fungal species at a concentration of 100 µg mL–1

Organic Reactions in Water

Velik je izazov provoditi organske reakcije u vodi. U posljednjem desetljeću broj znanstvenih istraživanja koja se bave proučavanjem vode kao zelenog otapala nastavio je eksponencijalno rasti. Osim što je jeftina, voda nije štetna za okoliš, a ponekad daje potpuno neočekivanu reaktivnost u kemijskim reakcijama. Postoji širok raspon organskih reakcija koje se mogu odvijati u vodi: od uobičajenih oksidoredukcijskih reakcija, reakcija koje uključuju karbokatione, pericikličkih reakcija, reakcija prijelaznih metala itd. Organske reakcije u vodenom mediju primjenjuju se u kemiji ugljikohidrata i kemijskoj modifikaciji biomolekula. U novije vrijeme voda se upotrebljava kao medij u mikrovalnoj sintezi. Ovaj pregledni rad daje uvid u važnost ovog područja budući da se organske reakcije u vodi kao otapalu odvijaju po principima zelene kemije.It is an exceptional challenge to perform organic reactions in water. In the last decade, scientific research in the field of water as a green solvent has continued to grow exponentially. Apart from being cheap, water is harmless to the environment and sometimes gives completely unexpected reactivity in reactions. There is a wide range of organic reactions that can take place in water: from common oxidation-reduction reactions, reactions involving carbocations and carbocations, pericyclic reactions, transition metal reactions, and others. Organic reactions in an aqueous medium are used in the chemistry of carbohydrates and in the chemical modification of biomolecules. More recently, water has been used as a medium in microwave synthesis. This review gives an insight into the importance of this field, since organic reactions in water as a solvent, take place according to the principles of green chemistry

Microwave-assisted Quaternization of Various Pyridine Derivatives and their Antibacterial Activity

In this study, reactions of quaternization under microwave heating of pyridine, α-picoline, pyridine-4-aldoxime, pyridine-2-aldoxime, nicotinamide, isonicotinamide and pyridoxal oxime with different electrophiles: 2-bromo-4\u27-nitroacetophenone, 2-amino-4-chloro-methylthiazole hydrochloride, methyl iodide, 1,3-diiodopropane and 1,3-dibromopropane are reported. The synthesis yield by microwave dielectric heating is improved and reaction time shortened compared to conventional heating. The structure of obtained molecules were analyzed and determined by 1D and 2D NMR spectroscopy methods, IR spectroscopy and mass spectrometry. The highest antibacterial activity against two Gram-positive and two Gram-negative bacteria strains has been found for 1-[2-(4-nitrophenyl)-2-oxoethyl]pyridinium bromide (2). This work is licensed under a Creative Commons Attribution 4.0 International License

A Rapid Microwave Induced Synthesis of Isonicotinamide Derivatives and their Antifungal Activity

Ten novel isonicotinamide derivatives were prepared by quaternization reactions of isonicotinamide with methyl iodide and nine differently substituted 2-bromoacetophenones under rapid microwave irradiation of 10 minutes. The microwave preparations were significantly faster and with yields higher up to 8 times, than the preparations by conventional method. The structures of synthesized molecules were determined by one- and two-dimensional NMR and IR spectroscopy, mass spectrometry and elemental analysis. Antifungal activity of all compounds was tested in two different concentrations (10 and 100 µg mL–1) against Fusarium oxysporum, Fusarium culmorum, Macrophomina phaseolina and Sclerotinia sclerotiorum in vitro. From the antifungal assay it can be seen that the most prepared compounds have moderate to weak activity against M. phaseolina and F. culmorum. A very high inhibitory rate was observed against S. sclerotiorum, 62–87.5 % in concentration of 10 µg mL–1 and 83.7–93.2 % in concentration of 100 µg mL–

Ružička days : International conference 16th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2)