Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C−H Bond Activation

Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe)2]2 and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

本研究采用二(μ-氯)二[氯(环辛烯)合铑(I)]([RhCl(coe)₂]₂)与手性亚磷酰胺配体组成的催化体系，成功实现了与亚胺导向基处于间位的、连有烯基的芳香亚胺的高对映选择性分子内邻位烷基化反应。对于包含1,1-二取代烯烃、1,2-二取代烯烃以及三取代烯烃的各类底物，其环化反应的对映选择性均大于90% ee，且各底物均能顺利完成环化。带有Z型烯烃异构体的底物的环化反应效率远高于带有E型烯烃异构体的底物。这一发现进一步使得部分含有Z/E混合烯烃的底物可通过铑催化的烯烃异构化过程实现高立体选择性分子内烷基化，且反应优先发生Z异构体的环化。