Authors:Michael S. Placzek, Jessica M. Chmielecki, Connor Houghton, Alyssa Calder, Charlotte Wiles and Graham B. Jones
Continuous-flow methodologies have been applied to the synthesis of a number of fluorinated alkynyl arenes and heteroarenes. Through a series of optimizations reagent stoichiometry and reaction time were improved and substrate specificity was interrogated. Using optimized conditions under copper-free Sonogashira type couplings readily available arene building blocks were derivatized with fluoroalkynyl side chains in <10 min. Given the rapidity of the process and the enhanced purity profile of the products an immediate application of the work is in the development of 18F labeled versions of the agents for subsequent use in positron emission tomography (PET) imaging. A homolog of the Alzheimer's disease imaging agent Fallypride® was prepared using the methodology and additional analogs was identified.
Authors:R.V Salamon, É. Vargáné-Visi, Cs.D. András, Zs. Csapóné Kiss and J. Csapó
The addition of synthetic CLA is a possible way in order to compose foods enriched with conjugated linoleic acids (CLAs). The most environmental friendly methods for CLA synthesis are based on microbial biosynthesis. With homogeneous catalysis using organometallic catalysts (Ru and Rh complexes) high (approximately 80%) yields were obtained with high selectivity related to bioactive isomers. The heterogeneous catalysis has the advantage that at the end of the reaction there is no need for a supplementary separation operation or recycling of the catalyst. In heterogeneous process, the maximum yield may even be higher than 90% and the selectivity remains quite high as the reaction conditions are optimized. The substrates for obtaining CLAs are, in general, linoleic acid or alkyl linoleates and the catalysis is acidic. The yield and the selectivity depend on the strength and the type of acidic sites, as well as on the size distribution of the particles. Beside the existing catalytic methods, a photocatalytic process with UV and visible light irradiation with iodine promoter can be applied.
Authors:Hasret Yalgin, Denis Luart and Christophe Len
Production of quinaldine and derivatives is proposed using sulfuric acid as commercial homogeneous acid catalyst in water in continuous flow chemistry. This approach is a rapid, practical and green route for the synthesis of 2-methylquinolines and permit to obtain the target compounds in 39–91% yields.
Authors:Anne-Catherine Bédard, Jeffrey Santandrea and Shawn K. Collins
The continuous-flow synthesis of a series of 11- to 26-membered macrocycles via copper-catalyzed azide-alkyne cycloaddition is reported. The approach employs homogeneous catalysis to promote formation of triazole-containing macrocycles in good to excellent yields (65–90%) at relatively high concentration (30–50 mM) using a phase separation strategy.
Authors:Dorina Chambre, Maria-Raluca Szabo, C. Popescu and Cornelia Idiţoiu
Using a micro-calorimetrical DSC we have compared the acid-catalyzed inversion of sucrose in homogeneous and heterogeneous
systems. Acetic acid was chosen as catalyst for homogeneous system, and several carboxylic cationites were used as heterogeneous
catalysts. The kinetic apparent parameters (A, E, kap) for all the systems were calculated from DSC data with Friedmann’s method and catalytic constant, k323cat, was further inferred. We found that the specific catalyst efficiency, qcat, in heterogeneous system is over 5000 times higher than in case of homogeneous ones. The activity of heterogeneous carboxylic
systems is still about 30 times larger than those of a strong mineral acid in homogeneous catalysis.
The results indicate the high efficiency of heterogeneous systems for soft acid catalysis of the sucrose hydrolysis.
Authors:Anne G. D. Santos, Vinícius P. S. Caldeira, Mirna F. Farias, Antonio S. Araújo, Luiz D. Souza and Allan K. Barros
In this study, the physico-chemistry characterization and kinetic study of the thermal decomposition of sunflower oil and its biodiesel were carried out. Sunflower biodiesel was synthesized by the methanol route and basic homogeneous catalysis. The physicochemical characterization of the sunflower oil and biodiesel were performed according to standards set out in the ANP resolution, and both are in accordance to the specifications. The chromatographic analysis was obtained by GC-FID. The yield of conversion of 97.4 wt% of sunflower oil in methyl esters confirms the efficiency of the conversion of the fatty acids into esters. The thermal analysis was performed on a thermobalance, using heating rates of 5, 10, and 20 °C min−1. In these three rates, we observed a single well-defined step of mass loss that describes the volatilization and decomposition of the sunflower oil and the biodiesel. The kinetic study was performed using equations of approximation and integration methods such as Coats–Redfern, Van Krevelen, and Horowitz–Metzger. The kinetic parameters reaction order (n) and apparent activation energy (Ea), obtained by applying these method were correlated.
, B. R. Jermya, A. Aitania, J. Cejka, S. Al-Khattaf* Catalysis Today 2014 , 227 , 187–197
“Kinetics of cyclooctene hydroformylation for continuous homogeneouscatalysis” S. Güven, B. Hamers, R. Franke, M. Priske, M. Becker
Authors:Sangeeta Vijay Jagtap and Raj Madhukar Deshpande
reactions. Biphasic solvent systems are an extremely useful and practical means of overcoming the catalyst-product separation issues in homogeneouscatalysis [ 6 ] and have been successfully applied to number of reactions like hydroformylation, hydrogenation
relationship with concentrations of modifiers. These observations were coined nonlinear phenomena to separate it from the nonlinear effect (NLE) observed in homogeneouscatalysis. In the latter case of no proportionality between the enantiomeric excess ( ee