Knoevenagel-type Condensation Reactions Promoted By Organocatalyst

Organocatalyst is a kind of low molecule weight organic compound with the basic characters of catalyst and without metal ion. Because of advantages such as containing metal-free, so the organocatalyst has not the potential risk of leaching of toxic metal ion to the environment; generally has good catalytic activity, some might exhibit peculiar character and catalytic mechanism as enzyme; easily handled, can be performed in solution or air without the necessity of severe conditions like water-free and oxygen-free. The price is commonly cheap and it is designable due to its conveniently prepared, decorated and modified properties; simply separated from the reaction system and recycled, therefore, it attracts more and more attention from chemists in the world recently and becomes hot point in green chemistry.This thesis will introduce some research in organocatalyt promoted condensation reactions as follow:1. 2-amino-3-cyano-4-aryl-7,7-dimethyl-5-oxo-4H-5,6,7,8-tetrahydrobenzo[b]pyran derivatives are synthesized via aromatic aldehyde, malononitrile and dimedone's one-pot three-component tandem Knoevenagel-cyclocondensation reaction employing N-methylimidazole as organocatalyst with good to excellent yield between 83% to 98% by using ethanol as solvent, using water as solvent and grinding separately.2. Knoevenagel condensation reaction between aromatic aldehyde, malononitrile or ethyl cyanoacetate is promoted by organocatalyst N-methylimidazole. This method provides several advantages such as rapid reaction rate, convenient operation, high yields and simple work-up procedure.3. The mixed solvent of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate and water has efficiently promoted the synthesis of a variety of 5-arylmethylidene-4-oxo-2-thiothiazolidine from the corresponding aromatic aldehydes and rhodanine at room temperature in 80%-93% yields in 10 to 120 min. The present protocol offered several advantages including mild conditions, high yields, short reaction time, simple work-up procedure, moreover, the ionic liquid can be reusable.4.The three-component condensation reactions of aromatic aldehydes, 5,5-dimethyl-1,3-cyclohexanedione and ammonium acetate efficiently promoted by several ionic liquids under solvent-free condition to afford corresponding 9-Aryl-3,3,6,6-tetramethyl-1,2,3,4,5,6,7, 8,9,10-decahydroacridine-1,8-diones in good yields. This protocol offers several advantages including high yields, operational simplicity, minimal environmental impact.