Directive Effect of the 2- and 3-Axial Hydroxy Groups That Appeared in the Complex Metal Hydride Reduction of Cyclohexanones
作者:Yasuhisa Senda、Nobuhito Kikuchi、Ayuko Inui、Hiroki Itoh
DOI:10.1246/bcsj.73.237
日期:2000.1
significant directive effect of the 2-axial hydroxy group appeared in the LiAlH4, NaBH4, and Zn(BH4)2 reduction of cyclohexanone, while the 3-axial hydroxy group exhibited a steric hindrance. The distance between the carbonyl carbon and the hydroxy group which interacts with the hydride reagent is mainly responsible for such a difference. In the reduction of Na[B(OAc)3H], both the 2- and 3-axial hydroxycyclohexanones
2-轴羟基在LiAlH4、NaBH4和Zn(BH4)2还原环己酮时表现出显着的定向作用,而3-轴羟基则表现出空间位阻。羰基碳和与氢化试剂相互作用的羟基之间的距离是造成这种差异的主要原因。在 Na[B(OAc)3H] 的还原反应中,2-轴和 3-轴羟基环己酮都只得到氢化物从羟基侧接近的产物。这种立体选择性的关键点是形成 Na[B(OAc)2(OR)H],通过将乙酸根离子与醇盐进行交换,Na[B(OAc)2(OR)H] 的反应性远高于母体氢化物。