Expanding the Toolbox of Heterogeneous Asymmetric Organocatalysts: Bifunctional Cyclopropenimine Superbases for Enantioselective Catalysis in Batch and Continuous Flow
作者:Costanza Leonardi、Arianna Brandolese、Lorenzo Preti、Olga Bortolini、Eleonora Polo、Paolo Dambruoso、Daniele Ragno、Graziano Di Carmine、Alessandro Massi
DOI:10.1002/adsc.202100757
日期:2021.12.21
A strategy for the immobilization of chiral 2,3-bisaminocyclopropenium salt (pre-catalyst) onto polystyrene and silica supports is presented together with a suitable procedure for the conversion into the corresponding cyclopropenimine superbase catalysts. The activity and recyclability of polystyrene- and silica-supported cyclopropenimines were initially tested under batch conditions in a model Michael
将手性 2,3-双氨基环丙烯盐(预催化剂)固定在聚苯乙烯和二氧化硅载体上的策略以及用于转化为相应环丙烯亚胺超强碱催化剂的合适程序。聚苯乙烯和二氧化硅负载的环丙烯亚胺的活性和可回收性最初是在分批条件下在迈克尔加成模型中测试的,检测出可比较的效率,但后者多相催化剂具有优异的稳定性(5 个循环,累积 TON 为 27.1)。在甘氨酸亚胺与不同迈克尔受体的反应中,优选的二氧化硅负载的环丙烯亚胺的表现与可溶性对应物非常相似(48-92% 产率;60-98% ee),它可以用作制造固定床中反应器(耐压不锈钢柱)的填充材料。连续流实验具有令人满意的长期稳定性(运行 24 小时),转换效率和对映选择性不变。
Phase-Transfer and Other Types of Catalysis with Cyclopropenium Ions
作者:Jeffrey S. Bandar、Anont Tanaset、Tristan H. Lambert
DOI:10.1002/chem.201500124
日期:2015.5.11
This work establishes the cyclopropeniumion as a viable platform for efficient phase‐transfer catalysis of a diverse range of organic transformations. The amenability of these catalysts to large‐scale synthesis and structural modification is demonstrated. Evaluation of the molecular structure of an optimal catalyst reveals some unique structural features of these systems. Finally, a discussion of