Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
Chemistry. 2011 May 16;17(21):5908-20. doi: 10.1002/chem.201003278. Epub 2011 Apr 14.
A versatile reducing agent, diimide, can be generated efficiently by the aerobic oxidation of hydrazine with neutral and cationic synthetic flavin catalysts 1 and 2. This technique provides a convenient and safe method for the aerobic reduction of olefins, which proceeds with 1 equiv of hydrazine under an atmosphere of O(2) or air. The synthetic advantage over the conventional gas-based method has been illustrated through high hydrazine efficiency, easy and safe handling, and characteristic chemoselectivity. Vitamin B(2) derivative 6 acts as a highly practical, robust catalyst for this purpose because of its high availability and recyclability. Association complexes of 1b with dendritic 2,5-bis(acylamino)pyridine 15 exhibit unprecedented catalytic activities, with the reduction of aromatic and hydroxy olefins proceeding significantly faster when a higher-generation dendrimer is used as a host pair for the association catalysts. Contrasting retardation is observed upon similar treatment of non-aromatic or non-hydroxy olefins with the dendrimer catalysts. Control experiments and kinetic studies revealed that these catalytic reactions include two independent, anaerobic and aerobic, processes for the generation of diimide from hydrazine. Positive and negative dendrimer effects on the catalytic reactions have been ascribed to the specific inclusion of hydrazine and olefinic substrates into the enzyme-like reaction cavities of the association complex catalysts.
一种多功能还原剂二酰亚胺可以通过肼在中性和阳离子合成黄素催化剂 1 和 2 的有氧氧化高效生成。这种技术为烯烃的有氧还原提供了一种方便、安全的方法，在氧气或空气的气氛下，使用 1 当量的肼进行反应。与传统的基于气体的方法相比，该方法具有高肼效率、易于安全处理和特征选择性等优点。维生素 B(2)衍生物 6 因其高可用性和可回收性而成为该目的的一种非常实用、强大的催化剂。1b 与树枝状 2,5-双（酰氨基）吡啶 15 的缔合配合物表现出前所未有的催化活性，当使用更高代的树枝状作为缔合催化剂的主体对时，芳香族和羟基烯烃的还原速度显著加快。在用树枝状催化剂对类似的非芳香族或非羟基烯烃进行类似处理时，观察到明显的延迟。控制实验和动力学研究表明，这些催化反应包括从肼生成二酰亚胺的两个独立的厌氧和需氧过程。正树状和负树状效应对催化反应的影响归因于肼和烯烃底物特异性地包含在缔合配合物催化剂的酶样反应腔中。
