Development of micelle-like catalyst for aqueous-media organic synthesis

通过4，4 ′-二羟基-2，2 ′-联吡啶与聚芳醚树枝状基元的偶联反应，合成了一系列以2，2 ′-联吡啶为核的树枝状配体。相应的树枝状Cu（OTf）_2催化剂用于Diels-Alder反应和三组分缩合反应。树枝状Cu（OTf）_2催化的Diels-Alder反应可以顺利进行，且催化剂可以重复使用而不会因再沉淀而失活。三组分缩合反应，如曼尼希型反应不仅在二氯甲烷中，而且在水中也进行。此外，在Diels-Alder反应和水介质三组分缩合反应中都观察到了对化学产率的正树枝化效应。结果表明，将刘易斯酸固定在树枝状大分子的核位上，可用于水相容性刘易斯酸催化剂的设计。

A series of dendritic ligands with a 2,2'-bipyridine core was synthesized through the coupling of 4,4'-dihydroxy-2,2'-bipyridine with poly(arylether) dendrons. The corresponding dendritic Cu(OTf)_2 catalysts were used for Diels-Alder and three-component condensation reactions. The dendritic Cu(OTf)_2-catalyzed Diels-Alder reaction proceeded smoothly, and these dendritic catalysts could be recycled without deactivation by reprecipitation. Three-component condensation reactions such as Mannich-type reactions also proceeded not only in dichloromethane but also in water. Furthermore, a positive dendritic effect on chemical yields was observed in both Diels-Alder reactions and aqueous-media three-component condensation reactions. It was found that the immobilization of Lewis acids on dendrimers at the core position is suitable for the design of water-compatible Lewis acid catalysts.