Study On The Piperidine Catalyzed Synthesis Of Substituted 2-amino-2-chromenes By Microwave Irradiation

During the last few years, microwave irradiation as an efficient thermal energy source is becoming a standard technique in various fields of chemistry. Especially in the application in organic chemistry. The catalytic mechanism and characteristic of the microwave irradiation to organic reactions and the recent progress in the research and application of the microware technique in organic synthesis are reviewed. Synthesis of chemical compounds' which normally require long reflux time can be achieved conveniently and very rapidly in microware oven. Compared with the classical heating methods as reported in literature, the benefit of microwave irradiation includes short reaction time, high yields, pure products and easier workup. The use of microwave energy to activate organic reactions has been taking a new dimension very recently. It has been used for a great variety of organic reaction as esterification and saponification, sulfonation, oxidation, hydrolysis, olefin addition, replacement, condensation, alkylation, rearrangement, Diels-Alder reaction, Reformatsky reaction, Knovenagel reaction, Perkin reaction, Deckmann reaction, Witting reaction, Bischler-Napieraski reaction, Protection and deprotection, concerted reaction, cyclization and ring-opening, etherification, etc.Since 1986, the research of microwave promoting organic reactions has been developed into a new famous felids, which is Microwave-Induced Organic Reaction Enhancement Chemistry. In this paper, we put the conception in the Knoevenagel reaction and cyclization reaction.Benzopyrans and their derivatives occupy an important place in the realm of natural and synthetic organic chemistry because of their biological and pharmacological properties such as antisterility and anticancer agents. In addition, polyfunctionalized benzopyrans constitute a structural unit of a number of natural products and because of the inherent reactivity of the inbuilt pyran ring are versatile synthons. Moreover, they can also be employed as cosmetics and pigments and utilized as potential biodegradable agrochemicals. These findings stimulated our interest in the synthesis of heterocyclic derivatives of these ring systems for their...