Enantioenriched bicyclo[4.1.0]hept‐2‐enes were synthesized by IrI‐catalyzed carbocyclization of 1,6‐enynes. No chiral ligands were used, CO and PPh3 were the only ligands bound to iridium. Instead, the stereochemical information was localized on the counterion of the catalyst, generated in situ by reaction of Vaska’s complex (trans‐[IrCl(CO)(PPh3)2]) with a chiral silver phosphate. Enantiomeric excesses
通过Ir I催化的1,6-烯炔的碳环化反应合成了对映体富集的双环[4.1.0]庚-2-烯。没有使用手性配体,CO和PPh 3是与铱结合的唯一配体。取而代之的是,立体化学信息位于催化剂的抗衡离子上,该催化剂是由Vaska络合物(反式[[IrCl(CO)(PPh 3)2 ]))与手性磷酸银反应而原位生成的。当使用这种催化混合物时,得到高达93%的对映体过量。31 P NMR和IR光谱表明,反式-[Ir(CO)(PPh 3)2 ] +的形成部分通过氯提取而发生。此外,密度泛函理论的计算支持该阳离子部分促进的6-内切-dig环化。手性磷酸根阴离子(O P *)控制通过形成与金属中心的松散的离子对的对映选择性,并建立一个C H⋅⋅⋅O 与基板P *氢键。这是非对称抗衡离子导向的过渡金属催化的罕见例子,代表了这种策略在CC键形成反应中的首次应用。
The cyclopentadienyl (Cp) group is a very important ligand for many transition‐metal complexes which have been applied in catalysis. The availability of chiralcyclopentadienyl ligands (Cpx) lags behind other ligand classes, thus hampering the investigation of enantioselective processes. We report a library of chiral CpxIrIII complexes equipped with an atropchiral Cp scaffold. A robust complexation
环戊二烯基(Cp)基团是许多在催化中应用的过渡金属配合物的重要配体。手性环戊二烯基配体(Cp x)的可用性落后于其他配体类别,因此妨碍了对映选择性过程的研究。我们报告了配备手性Cp支架的手性Cp x Ir III复合物的库。强大的络合程序可为Cp x Ir III络合物可靠地提供可调节的抗衡离子。在概念验证的应用中,含碘化物对烯炔的环异构化反应具有很高的选择性。脱氢哌啶稠合的环丙烷产物以良好的产率和对映选择性形成。
Chiral Tetrafluorobenzobarrelene Ligands for the Rhodium-Catalyzed Asymmetric Cycloisomerization of Oxygen- and Nitrogen-Bridged 1,6-Enynes
The long and winding Rhoad: The asymmetriccycloisomerization of nitrogen‐ and oxygen‐bridged 1,6‐enynes proceeded in the presence of a cationic rhodium complex that was coordinated by PPh3 and a chiral diene ligand to afford high yields of chiral 3‐aza‐ and 3‐oxabicyclo[4.1.0]heptenes and high enantioselectivities. TS=4‐toluenesulfonyl, Tf=trifluoromethanesulfonyl.
Chiral Diene-Phosphine Tridentate Ligands for Rhodium-Catalyzed Asymmetric Cycloisomerization of 1,6-Enynes
作者:Takahiro Nishimura、Yuko Maeda、Tamio Hayashi
DOI:10.1021/ol2013236
日期:2011.7.15
Asymmetriccycloisomerization of nitrogen-bridged1,6-enynes proceeded in the presence of a cationic rhodium complex coordinated with a chiral diene/phosphine tridentate ligand to give high yields of chiral 3-azabicyclo[4.1.0]heptenes with high enantioselectivity.