Ruthenium-Catalyzed Asymmetric Hydrohydroxyalkylation of Butadiene: The Role of the Formyl Hydrogen Bond in Stereochemical Control.
Ruthenium-Catalyzed Asymmetric Hydrohydroxyalkylation of Butadiene: The Role of the Formyl Hydrogen Bond in Stereochemical Control.
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DOI：
10.1021/jacs.5b04844
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发表时间：
2015-07-15
影响因子：
15
通讯作者：
Houk KN
中科院分区：
文献类型：
--
作者：
Grayson MN;Krische MJ;Houk KN
由 RuH2(CO)(PPh3)3、(S)-SEGPHOS 和手性磷酸原位生成的催化剂促进丁二烯的不对称氢羟烷基化并提供对映体富集的 α-甲基高烯丙醇。观察到的非对映选择性和对映选择性由手性膦和手性磷酸配体决定。密度泛函理论计算（M06/SDD-6-311G(d,p)-IEFPCM(acetone)//B3LYP/SDD-6-31G(d)）预测产物分布受碳-碳键形成动力学控制，并且该过程通过闭椅Zimmerman-Traxler型过渡结构（TS）发生。该 TS 产生的手性磷酸盐依赖性立体选择性是通过 TADDOL 衍生催化剂中磷酰氧和醛甲酰质子之间的氢键实现的。这种相互作用在相应的 BINOL 衍生系统中不存在，并且对醛发生相反的攻击。确定了影响立体化学控制的其他因素。
The catalyst generated in situ from RuH2(CO)(PPh3)3, (S)-SEGPHOS, and a chiral phosphoric acid promotes asymmetric hydrohydroxyalkylation of butadiene and affords enantioenriched α-methyl homoallylic alcohols. The observed diastereo- and enantioselectivities are determined by both the chiral phosphine and chiral phosphate ligands. Density functional theory calculations (M06/SDD-6-311G(d,p)-IEFPCM(acetone)//B3LYP/SDD-6-31G(d)) predict that the product distribution is controlled by the kinetics of carbon-carbon bond formation, and this process occurs via a closed-chair Zimmerman-Traxler-type transition structure (TS). Chiral phosphate-dependent stereoselectivity arising from this TS is enabled through a hydrogen bond between the phosphoryl oxygen and the aldehyde formyl proton present in TADDOL-derived catalysts. This interaction is absent in the corresponding BINOL-derived systems and the opposite sense of attack on the aldehyde occurs. Additional factors influencing stereochemical control are determined.