Nuove metodologie di sintesi di composti eterociclici di interesse biologico con reazioni Pd-catalizzate
Author(s)
De Salve, Ilse Maria Luce
Date Issued
September 10, 2008
Type
Doctoral Thesis
Abstract
Over the last few years, industry focused its efforts on the development of new technologies for pollution prevention. Thus green chemistry has been recognized as a a new approach to scientifically based
environmental protection. Green chemistry “is the design of chemical products and processes which reduce or eliminate the use and the generation of hazardous substances in the design, manufacture and application of chemical products”. In the last decades, palladium-catalyzed reactions have become an
important and extremely flexible tool for practicing organic chemists. As palladium chemistry is generally tolerant of a wide range of functionalities, it is applicable to complex molecules. Thus, a large number of fine chemicals and biologically active ingredients have been prepared in fewer steps and with less wastes than classical methods. Even the design of heterocyclic synthesis has been deeply influenced and modified by the
growing utilization of palladium catalysis, as testified by the wide amount of studies on the palladiumcatalyzed synthesis and functionalization of heterocycles.
In this context, during my doctorate activity, we investigated the construction of heterocyclic rings and the production of derivatives of heterocyclic compounds of biological interest through palladium-catalyzed reactions. In some cases, these synthesis have been performed in environmentally friendly solvents and
organic compounds present in agroindustrial wastes have been used as starting materials to achieve their “chemical valorization”.
Then, using our background on the Heck reaction it appeared to us particularly interesting to investigate the possibility to develop domino vinylic substitution/cyclization processes to obtain functionalised coumarins and 2-quinolones in molten salts, new reaction media having interesting green properties (no detectable vapour pressure, possible recycling, thermal robustness).
At the same time, we explored in more detail the Heck reaction of β,β-diarylacrylamides and the results obtained prompted us to investigate the utilization of this chemistry for the preparation of 2-quinolone
derivatives through an intramolecular carbon-nitrogen bond forming step. Concerning the cyclization step, the economic attractiveness of copper-based methods and the growing interest in copper-catalyzed
syntheses stimulated us to develop a copper-catalyzed protocol.
As part of our studies devoted to the construction of the benzo[b]furan skeleton via palladium-catalyzed cyclization of acetylenic precursors, we explored the extension of our alkyne chemistry to the preparation of lipophilic benzo[b]furan derivatives from cardanol, a natural renewable phenolic lipid obtained by vacuum
distillation of the by-product of the cashew tree (Anacardium occidentale L.) industry.
Finally, using catechins and epicatechins as substrates, organic resource obtained from wastes of wine industrial production, we investigated the utilization of the Suzuki reaction to obtain the corresponding
arylated catechin derivatives.
In all the synthetic protocols developed in this work we have taken advantage of several green chemistry principles. In fact, using palladium-catalysis it has been possible to maximize the incorporation of atoms and realize one-pot or domino processes. Raw material of feedstock and alternative no-toxic solvents have been used.
Additional information
Dottorato di ricerca in Scienze ambientali
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