Investigation On The Synthesis Of Quinolines And Quinolones Under Solvent-Free And In Water Conditions

For the stringent and growing environmental regulations, one of the main duties assigned to the organic chemist is to conduct research in such a way that it preserves the environment and to develop procedures that are both environmentally and economically acceptable. One major objective is therefore to simplify and adjust the classical procedures in order to keep pollution effects to a minimum, together with a reduction in energy and raw materials consumption. Solvent-free techniques hold a strategic position as solvents are very often toxic, expensive, and problematic to use and to remove. Microwave irradiation is a powerful synthetic tool to simplify the experimental operation, improve yields and enhance the rates of classical organic reactions. Meanwhile the use of water as a reaction medium has a number of advantages such as the cheapest solvent available on earth, being non-hazardous and non-toxic to the environment, easy product isolation by simple phase separation. These techniques represent a clean, economical, efficient and safe procedure, which can lead to substantial savings in money, time and products. Thus, to perform organic reactions using solvent-free techniques coupled with microwave irradiation or conventional heating and to utilize water as reaction medium are very promising ways to reach this goal. The main work presented in this dissertation is about the investigation on the synthesis of quinolines and quinolones carried out under solvent-free and in water conditions. The contents are listed as the following:1. A rapid and efficient method for the preparation of various poly-substituted quinolines has been developed through the Friedl(a|¨)nder condensation of 2-aminoarylketone or 2-aminoarylaldehyde with carbonyl compounds in the presence of p-toluene sulphonic acid in very high yields, which was achieved by both microwave irradiation and conventional heating technique under completely solvent-free conditions. The effects of some Lewis acid catalysts on these reactions have also been investigated. In order to draw a direct comparison between microwave irradiation and conductive heating, a few selected reactions were carried out at an identical temperature (100 °C) in a modern microwave synthesizer. By comparison with the experimental results, the microwave irradiation protocol is generally faster than the conventional heating at the same temperature to reach comparable yield, reflecting the specific non-thermal effects, which are not strong under microwave irradiation conditions. For the microwave-assisted reactions in a domestic microwave oven, the reaction time required could be even shorter than that in a modern microwave synthesizer. The good yields in a commercially available and cheap domestic microwave oven can be reproduced in a more modern microwave synthesizer and thus can be transferred to it. In each of these two methods, the process is environmentally benign, the experimental procedure is very simple and the product isolation is easy. Furthermore, all the products obtained by these methods were highly pure and in most cases no further purification was needed. Both of these two protocols can be applied to a wide range of substrates, tolerating the presence of halogen, ketone and ester groups. These methods not only afford significant improvements in reaction rates and yields but also present a more straightforward and...