离子液体介质中FeCl3•6H2O催化下芳香醛与5,5-二甲基-1,3-环己二酮的缩合反应

考察了在离子液体1-正丁基-3-甲基咪唑四氟硼酸盐(bmim]BF₄])介质中, 芳香醛与5,5-二甲基-1,3-环己二酮的缩合反应. 实验结果表明, 在催化量的FeCl₃?6H₂O存在下, 该反应可高产率地生成氧杂蒽二酮类化合物3; 而在TMSCl/FeCl₃?6H₂O复合催化体系的催化下, 则得到氧杂蒽二酮类化合物的开环衍生物4, 反应具有非常好的选择性. 该论文提供的方法操作简单、产率高、选择性好而且对环境友好. 在反应结束后, 所用催化剂及离子液体都很容易回收, 并能有效重复使用.

FeCl3•6H2O Catalyzed Con-densation of Aromatic Aldehydes with 5,5-Dimethyl-1,3-cyclohexanedione in Ionic Liquids

The reaction of aromatic aldehydes 1 with 5,5-dimethyl-1,3-cyclohexanedione 2 was investi- gated by using bmim]BF4] as a reaction medium. It was found that without additional catalyst this reaction could only be realized at elevated temperature and gave a mixture of xanthenediones 3 and their ring-opening derivatives 2,2'-arylmethylenebis-(3-hydroxy-5,5-dimethyl-2-cyclohexen-1-one) (4) in poor yields. On the other hand, when it was carried out in the presence of FeCl36H2O, its selectivity and effi- ciency could be improved significantly and compound 3 could be obtained exclusively with high yield under optimized reaction conditions. Further study showed that when the same reaction was carried out under the catalysis of a combination of trimethylchlorosilane and FeCl36H2O, compound 4, without any contamina- tion of 3, was obtained in good yield.