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首页> 外文期刊>Chemistry: A European journal >pH-Dependent Catalytic Activity and Chemoselectivity in Transfer Hydrogenation Catalyzed by Iridium Complex with 4,4 '-Dihydroxy-2,2 '-bipyridine
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pH-Dependent Catalytic Activity and Chemoselectivity in Transfer Hydrogenation Catalyzed by Iridium Complex with 4,4 '-Dihydroxy-2,2 '-bipyridine

机译：铱配合物4,4'-二羟基-2,2'-联吡啶催化的转移加氢中pH依赖的催化活性和化学选择性

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摘要

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 of the DHBP complex, which can be more than 1000 times the value of the unsubstituted analogue, are obtained (up to 81000 h(-1) at 80 degrees C). In addition, the DHBP catalyst exhibits pH-dependent chemoselectivity for alpha,beta-unsaturated carbonyl compounds. Selective reduction of the C=C bond of enone with high activity are observed under basic conditions. The ketone moieties can be reduced with satisfactory activity under acidic conditions. In particular, pH-selective chemoselectivity of the C=O versus C=C bond reduction was observed in the transfer hydrogenation of cinnamaldehyde.
机译：甲酸水溶液中铱催化剂与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81000 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。特别地，在肉桂醛的转移氢化中观察到C ＝ O对C ＝ C键还原的pH选择性化学选择性。

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