AbstractIsomeric “compact” and “expanded” dendrimers functionalized with L‐prolinamide catalytic units at the periphery were compared as catalysts to monomer controls in the organocatalytic direct aldol condensation. A positive dendritic effect that amplifies the stereoselectivity of the direct aldol condensation was observed for dendrimers 3 and 4, compared with lower molecular weight catalysts L‐prolinani‐lide 1 and G1 dendron 2. The difference in the compactness between 3 and 4 appears to have less impact on the stereoselectivity than the preorganized multivalency of the dendritic catalysts.
摘要在有机催化直接醛醇缩合反应中,比较了外围具有 L-脯氨酰胺催化单元的同分异构 "紧凑型 "和 "扩展型 "树枝状聚合物作为催化剂与单体对照的效果。与分子量较低的催化剂 L-prolinani-lide 1 和 G1 树枝状分子 2 相比,树枝状分子 3 和 4 具有积极的树枝状效应,可提高直接醛醇缩合的立体选择性。与树枝状催化剂的预组织多价性相比,3 和 4 的紧密性差异对立体选择性的影响似乎较小。