Two Novel Catalyst For Knoevenagel Reaction

Knoevenagel condensation reaction products were used in many fields. For example: coumarin compounds and their derivatives; allyl benzyl adiponitrile; Naphthalene es:er diaminofurazan amine; p-methoxyl cinnamic acid ester. As an important reaction of me organic synthesis reaction type, its catalysts were always valued. For example:pyridine; 1-butyl-3-methylimidazolium hydroxide; PEG-supported piperazine; NaZnPO4, acidic eolites, Al2O3. In addition, physical auxiliary methods were also applied to Knoever agel reactions catalyzed study, ultrasonic wave, microwave method, grinding method.In recent years, because the strengthening of environmental protection consciousness, more and more scientists pay attention on the solvent reaction. At room temperature under solvent-free, koevenagel reaction caused numerous chemists study due tc the simple operation. Melamine has a specific molecular structure-insolube in water and most organic solvents. After the reaction, the target product can quickly separate. Also it is easy to handle, easy to purchase, the price is reasonable. Diethylamine-modified PEG600 was synthesized as a Knoevenagel catalyst. The structures of the product were confined by IR. MS, HNMR in this paper. The major study as follows:i. Melamine as the koevenagel reaction catalystThe catalytic properties of melamine were studied. We choose different substituted aromatic aldehydes with malononitrile, ethyl cyanoacetate, diethyl malonate. The experimental results show that:the different aldehyde groups and methylene groups have an important influence on the catalytic of melamine. Melamine can’t catalyz(?) the reaction of diethyl malonate with benzaldehyde. The reuse of melamine was investigated, in which 4-methylbenzaldehyde and ethyl cyanoacetate were chosen as the substrates. It was shown that melamine still can catalyze this reaction without lose of activity even after five runs.ii. Diethylamine-modified PEG-600 as knoevenagel reaction catalystDiethylamine functionalized PEG600 is synthesized by two steps-dichloro substituted PEG600 and diethylamine functiongalized PEG600. We used modified PEG as catalyst of knoevenagle reaction. The catalyst was added the misture of aldehyds and active methylene compound. The table show that, as a new kind of base, diethylamine functionalized PEG600 makes the knoevnagel condensation at room temperature with good to excellent yield. The reaction performances were also carried out in prence of PEG600, the dichloro-modified PEG600 and the diethylamine-modified PEG600. The experiments show that PEG600 and diethylamine-modified PEG600 can catalyst the reaction. But PEG600 required much longer time. However, the reaction doesn’t proceed under dichloro-modified PEG600. Accordingly, the catalyst can be easily recycled and reused without moticeably decreasing in productivity.