Condensation And Oxidation Reactions Of Aldehydes In Water

One of the most promising approaches in green chemistry is to utilize water as the reaction medium, which presents a clean, economical, and environmental-safe protocol. In fact, more and more reactions have been reported to proceed smoothly and efficiently in water. Furthermore, due to the low solubility of common organic compounds in water, the use of water as a solvent often makes the purification of products very easy by simple filtration or extraction. With this in mind, we investigated organic reactions in pure water. The main work in this dissertation is about the investigation on the reaction of carbonyl compounds in water. The contents are listed as the followings:1. We have developed a new protocol for the eco-friendly and efficient synthesis of a series of 1,4-dihydropyridines with potential biological activities. This practical synthesis is realized by the one-pot reactions of aldehydes with ammonium acetate and 1,3-dicarbonyl compounds such as alkyl acetoacetate, 5,5-dimethyl-1,3-cyclohexanedione, 1,3-cyclohexanedione and 2,4-pentanedione in refluxing water. The yields of 1,4-dihydropyridines are generally better than those reported previously. We do not use any organic solvents or additives in the reaction process, and employ water as a cheap and "green" solvent for the reaction medium. The work-up procedure is simple filtration. Therefore, our current process is a more straightforward and environmentally benign protocol.2. The synthesis and aromatization of a series of 1,4-dihydropyridines have been achieved by the one-pot reactions of aldehydes with 1,3-dicarbonyl compounds and ammonium acetate followed by oxidation with either ferric trichloride or potassium permanganate in refluxing water. The current procedure does not use any organic solvent, and it simplifies the formerly reported procedures. Therefore, it is a more straightforward and environmentally benign protocol, which can be a practical alternative method for synthesis of this kind of compounds.3. We have developed a novel and benign reaction of aromatic aldehydes, ethylenediamine and oxone in pure water. In this protocol, aldoximes were obtained unexpectedly with excellent yields. This transformation provides a new access to the preparation of aldoximes.