pH-Dependent Catalytic Activity and Chemoselectivity in Transfer Hydrogenation Catalyzed by Iridium Complex with 4,4′-Dihydroxy-2,2′-bipyridine
作者:Yuichiro Himeda、Nobuko Onozawa-Komatsuzaki、Satoru Miyazawa、Hideki Sugihara、Takuji Hirose、Kazuyuki Kasuga
DOI:10.1002/chem.200801568
日期:2008.12.8
Transfer hydrogenation catalyzed by an iridium catalyst with 4,4'-dihydroxy-2,2'-bipyridine (DHBP) in an aqueous formate solution exhibits highly pH-dependent catalytic activity and chemoselectivity. The substantial change in the activity is due to the electronic effect based on the acid-base equilibrium of the phenolic hydroxyl group of DHBP. Under basic conditions, high turnover frequency values
在甲酸水溶液中用铱催化剂与4,4'-二羟基-2,2'-联吡啶(DHBP)催化的转移加氢表现出高度的pH依赖性催化活性和化学选择性。活性的显着变化归因于基于DHBP酚羟基的酸碱平衡的电子效应。在基本条件下,可获得DHBP复合物的高周转频率值,该值可能是未取代类似物值的1000倍以上(在80摄氏度时高达81 000 h(-1))。另外,DHBP催化剂对α,β-不饱和羰基化合物表现出pH依赖性的化学选择性。在碱性条件下观察到具有高活性的烯酮的C = C键的选择性还原。可以在酸性条件下以令人满意的活性还原酮部分。