Developments in the synthesis of polyfunctionalized heteroaromatic systems and applications in asymmetric catalysis

Heterocycles are an important class of organic compounds, due to their occurrence in almost all the biological macromolecules. For this reason, the large majority of pharmaceuticals are synthetic heterocycles which have found widespread use as anticancer agents, analeptics, analgesics, hypnotics, and vasopressor modifiers. Other heterocycles serve as pesticides, insecticides, herbicides, and rodenticides. As result, more than 90% of new drugs contain heterocycles. Other applications include dyestuffs, copolymers, solvents, photographic sensitizers and developers, and antioxidants and vulcanization accelerators in the rubber industry. The aim of this work is to provide a contribution to the vast area of heterocyclic chemistry. It could be divided in two parts: in the first one new strategies for the synthesis of heteroaromatic-containing compounds are proposed. In the second part, some applications of heterocyclic compounds in organic asymmetric synthesis have been identified. For the construction of substituted heterocycles, the ability of CeCl3 to promote carbon-heteroatom bond-forming has been exploited. Recent studies in our laboratories have shown that commercially available reagents such as CeCl3.7H2O can be used without any special caution, and its activity increases dramatically in the presence of an iodide source, such as NaI or CuI, resulting in shorter reaction times, diminished byproduct formation, and improved yields and purity of products. It is very well known that microwave irradiation can shorten the reaction time of many organic reactions and it is a convenient method to promote rapid reactions with much less energy. During our investigation we discovered that the long time (in order of days) of reactions in thermal conditions, are reduced at few hours by employing microwave-assisted procedure. Besides, higher yields may be possible increasing the rate of reactions by effect of microwave irradiation.