Solid Acid As A Catalyst In Organic Reaction

In response to the main aim of green chemistry, we can’t use toxicsubstances, and we can’t produce waste water, waste gas and the waste, we must from thesource to weaken or eliminate the pollution’ maximize the utilization of resources, protectenvironment, and promote ecological balance. In numerous organic synthesis reactions，thechoice of using non-toxic harmless catalysts is the prerequisite to realize green chemicalprocess. But the commonly used traditional acid catalysts such as sulfuric acid, phosphoricacid, hydrofluoric acid, etc., although such catalysts are readily available and inexpensive,and so the catalytic effect of the good, however, they are difficult to separate from thereaction and the product, and has certain corrosion damage on the reaction container,complicated post-processing step, poor selectivity, the catalyst after the reaction are noteasy to recycle, which contrary to green chemistry concept championed by the people, theycan not adapt to the current trend of economic development and environmental protection.The solid acid catalyst shows their uniqueness in these areas. It can overcome thedeficiencies of traditional acid catalyst, they can also be recycled and used, and mildreaction conditions, simple operation, less hazardous to the environment, in the majority oforganic synthesis reactions exhibit selective and eiffcient, being used in great quantities.This selection of the trichloroacetic acid，ammonium chloride, humic acid as acatalyst synthesis, were synthesized respectively p-enaminones compounds,3,4-dihydropyrimidin-2-one compounds,1,4-dihydropyridine compounds,2-substitutedbenzoxazole compounds, specific as follows:(1)Using trichloroacetic acid catalyst and ethanol as solvent, aromatic miinecompounds reacted with p-diketone compounds to synthesize p-enamine ketonescompounds. This method is eiffcient, green and safe, and enjoys convenient operation, andhigh yields;(2)Using humic acid catalyst and ethanol as solvent, reacted with aldehyde, urea andethyl acetoacetate, heated under reflux, synthesis of3,4-dihydro-2-ketones by one-potreaction. This method is simple，efficient, and the catalyst can be recycled, environmentalpollution; (3)Using humic acid catalyst and ethanol as solvent, ethyl acetoacetate, aldehydesand ammonium acetate are used as reactants, heated under reflux, synthesis of1,4-dihydropyridine compounds by one-pot reaction; This method with high yield, goodcatalytic activity, and the catalyst can be recycled, environmental protection, and meets therequirements of green chemistry;(4)Using humic acid catalyst and ethanol as solvent, and the catalyst involved in thereaction of o-aminophenol and aldehydes, heated under reflux，synthesis of2-substitutedbenzoxazole by one-pot reaction.This kind of reaction with high yield，safety andconvenient operation, the catalyst can be recycled.lt is an excellent way to synthesis of2-substituted benzoxazoles.