Inversion or Retention? Effects of Acidic Additives on the Stereochemical Course in Enantiospecific Suzuki–Miyaura Coupling of α-(Acetylamino)benzylboronic Esters
The stereochemicalcourse of the stereospecific Suzuki-Miyaura coupling of enantioenriched α-(acetylamino)benzylboronic esters with aryl bromides can be switched by the choice of acidic additives in the presence of a Pd/XPhos catalyst system. Highly enantiospecific, invertive C-C bond formation takes place with the use of phenol as an additive. In contrast, high enantiospecificity for retention of
在 Pd/XPhos 催化剂体系的存在下,可以通过选择酸性添加剂来切换对映体富集的 α-(乙酰氨基)苄基硼酸酯与芳基溴的立体定向 Suzuki-Miyaura 偶联的立体化学过程。使用苯酚作为添加剂可形成高度对映体的、倒置 CC 键。相比之下,在 Zr(Oi-Pr)(4)·i-PrOH 作为添加剂存在的情况下,实现了构型保留的高对映特异性。
Iridium−Monodentate Phosphoramidite-Catalyzed Asymmetric Hydrogenation of Substituted Benzophenone N−H Imines
Homogeneous asymmetric hydrogenation of unprotected benzophenone N-H imines 1a-r using 1r-benzyl-N-methyl-MonoPhos as a catalyst provides chiral amines 2a-r in 80-96% yield with enantioselectivities up to 98% ee (18 examples) for ortho-substituted substrates.