Diastereo‐ and Enantioselective Hydrogenation of α‐Amino‐β‐Keto Ester Hydrochlorides Catalyzed by an Iridium Complex with MeO‐BIPHEP and NaBAr
<sub>F</sub>
: Catalytic Cycle and Five‐Membered Chelation Mechanism of Asymmetric Hydrogenation
作者:Tsukuru Maeda、Kazuishi Makino、Masamichi Iwasaki、Yasumasa Hamada
DOI:10.1002/chem.201001298
日期:2010.10.18
Ir‐catalyzed asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides is described. This reaction proceeds through a dynamic kinetic resolution to produce anti‐β‐hydroxy‐α‐amino acid esters in a high diastereo‐ and enantioselective manner. Mechanistic studies have revealed that this unique asymmetric hydrogenation proceeds through reduction of the ketone moiety via the five‐membered transition state
描述了Ir催化的α-氨基-β-酮酸酯盐酸盐的不对称加氢反应的发展。该反应通过动态动力学拆分进行以产生抗-β-羟基-α-氨基酸酯,具有非对映和对映选择性高的方式。机理研究表明,这种独特的不对称氢化是通过经由五元过渡态还原酮部分而进行的,该五元过渡态涉及酮的氧与胺官能团的氮之间的螯合。氢压力和立体选择性之间的关系研究已经揭示了两种依赖于氢压力的机理。在低氢气压力(<15 atm)下,反应速率随氢气压力成比例增加。然而,在高氢条件下,反应速率随着氢压力的增加而呈指数增长,这表明两个或多个氢原子的参与。