Catalytic Asymmetric Hydrogenation of<b><i>α</i></b>-(Acetamido)acrylates Using TRAP Trans-Chelating Chiral Bisphosphine Ligands: Remarkable Effects of Ligand<b><i>P</i></b>-Substituent and Hydrogen Pressure on Enantioselectivity
作者:Ryoichi Kuwano、Masaya Sawamura、Yoshihiko Ito
DOI:10.1246/bcsj.73.2571
日期:2000.11
β-substituent and the ligand P-substituent as well as decreasing hydrogen pressure. The selectivity for the (R)-product in the reaction with EtTRAP-rhodium catalyst at 60 °C and 0.5 kg cm-2 of hydrogen pressure was as follows: R = H, 96% ee; R = Me, 92% ee; R = Ph, 77% ee; R = i-Pr, 57% ee. The remarkable steric and pressure effects caused a dramatic reversal of enantioselectivity in the reaction of methyl
用 [Rh(cod)2]BF4 和反式螯合手性双膦配体 (S,S)-2,2'-双 [( R)-1-(二烷基膦基)乙基]-1,1'-二茂铁[(R,R)-(S,S)-TRAPs]。在β-未取代或β-单取代的α-(乙酰氨基)丙烯酸酯[(E)-RCH=C(NHAc)CO2Me]的反应中,(R)-氢化产物的选择性随着底物β-空间需求的降低而增加取代基和配体 P 取代基以及降低氢压。在 60 °C 和 0.5 kg cm-2 氢气压力下与 EtTRAP-铑催化剂反应的 (R)-产物的选择性如下:R = H,96% ee;R = Me,92% ee;R = Ph,77% ee;R = i-Pr,57% ee。显着的空间和压力效应导致 2-(N-乙酰氨基) 肉桂酸甲酯 (R = Ph) 反应中对映选择性的显着逆转。例如,在 60 °C 和 0.1 kg cm-2 氢气压力下使用 EtTRAP 的选择性为 87%