Project description
Azasteroids, are invaluable compounds demonstrating fascinating potential applications for medicine, being a top and widely discussed research field in modern science. Many compounds containing nitrogen heterocycle moiety have demonstrated versatile biological activities, which include antiviral and anticancer, anti-inflammatory, antimicrobial, antifungal, antiandrogenic, antiprotozoal etc.
Over the last years, an increasing interest is paid to find new anticancer and antimicrobial (antibacterial, antifungal, antituberculosis) drugs. This is mainly because of the large variety of cancers described in the literature, which make therapy extremely complicated and often, inefficient. Moreover, because of the drug and multidrug resistance of cancer cells, the chemotherapy of cancer has become even more complicated.
Azaheterocycles derivatives with extended π-conjugation (especially those one condensed containing both a π-excessive azole and a π-deficient azine ring), are highly fluorescent compounds, most of them being ‘pure’ blue-emitting moiety. The absorption and fluorescence spectra of N-heterocycles are solvent sensitive and depend, on one hand, on the nature of the substituents at the heterocycle, and on the other hand, on the positions of the substituents. Investigations on the synthesis of new blue luminous materials for applications in electroluminescent displays have attracted great attention, but there are very few single component deep blue- and pure red-emitting dyes. Because of the industrial demand, it is still essential to find molecules, which exhibit high fluorescence, little self-quenching, proper energy levels, pure RGB colour and high stability.
Recently published comprehensive books and papers, indicate that the use unconventional methods (ultrasound (US) and microwave irradiation (MW)) in chemistry is in a continuously increasing, grace to the numerously advantages of it: environmentally friendly reactions (using small amounts of solvents and generating fewer side products); a feasible and efficient way to a large variety of classes of chemical compounds; realizing syntheses difficult or impossible to be done on other ways, with high yields and selectivity, high purity, etc.; lower costs of syntheses (dramatically decreasing of reaction time, saving energy and solvents, excess support bound reagent can be easily removed by filtration, avoiding cumbersome aqueous workups); monitoring of the reactions and analysis can be easy accomplished using standard methods (TLC, solution NMR, etc.). Under microwave, reaction could be carried out both under normal pressure as well as at high pressure.
As it could be seen from the literature data (selective publications, the most important, after year 2000), presently, there are some famous groups that are working in the field of fluorescence and, some others, in the field of microwave chemistry. Moreover, the importance and dynamic of these two fields is proved also by the high prestige and scientific level of these publications.
The array of transition-metal-catalyzed cross-coupling reactions can easily be considered nowadays cornerstones in the field of organic synthesis. Particularly, Heck, Sonogashira, Negishi, Stille, Suzuki cross coupling reactions are of great interest. As a common characteristic of these reactions, is the use of an organometallic catalyst based on palladium. Among them, a special attention is paid to palladium-catalyzed sp2-sp coupling reaction between aryl or alkenyl halides or triflates and terminal alkenes or terminal alkynes. In particular, the bimetallic palladium-copper catalyzed Sonogashira coupling has turned out to be a versatile and mild alkynylation of (hetero)aryl halides. This method has become one of the most important method to prepare arylalkynes and conjugated enynes, which are precursors for natural products, pharmaceuticals, and molecular organic materials.
The original and general Suzuki-Miyaura and Sonogashira coupling procedures involves the use of palladium-ligand complex as catalysts. Nevertheless, the high price of palladium renders commercial processes based on Pd less attractive. For these reasons, much recent attentions has been attracted on employing less expensive transition metal catalyst complexes, in particular, copper, to replace the palladium. In the presence of copper or copper-based nanocolloids, a variety of aryl halides coupled with phenylboronic acid efficiently in moderate to excellent yields. Nevertheless, only the couplings of aryl iodides were investigated when the catalyst was copper alone.
Nowadays, a special attention is paid to sequential transformations and multicomponent processes for synthetic, economical and ecological reasons. Especially, the three-component one-pot synthesis which combine Sonogashira coupling with cycloaddition reactions, has became on high interest.
I and our team from Iasi have a strong expertise in the field of nitrogen heterocycles and azasteroids as well as in the field of their application as fluorescent compounds and as potential candidates for applications in medicine. Also, we have a solid expertise in the field of microwave and ultrasound assisted reactions in organic synthesis.