碱在酮的不对称催化氢化反应中意想不到的潜在作用。几种关键催化中间体的合成与表征。
An unexpected possible role of base in asymmetric catalytic hydrogenations of ketones. Synthesis and characterization of several key catalytic intermediates.
作者信息
Hamilton Robin J, Bergens Steven H
机构信息
Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2.
出版信息
J Am Chem Soc. 2006 Oct 25;128(42):13700-1. doi: 10.1021/ja065460s.
The dihydrogen compound trans-[Ru((R)-BINAP)(H)(eta2-H2)((R,R)-dpen)]+ (2', BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl, dpen = 1,2-diphenylethylenediamine) is a proposed intermediate in asymmetric ketone hydrogenations. It quickly reacts at -80 degrees C with 1 equiv of the base KOtBu in 2-PrOH-d8/CH2Cl2-d2 under H2 to generate trans-Ru((R)-BINAP)(H)(2-PrO)((R,R)-dpen) (4). The alkoxide 4 does not react with H2 after hours under ambient conditions. Addition of 1 equiv of KOtBu to 4 produces a hydrogen bonded species 10 that reacts readily with H2 at -80 degrees C to generate the dihydride catalytic intermediate trans-[Ru((R)-BINAP)(H)2((R,R)-dpen)] (3'). Addition of 1 equiv of ((CH3)3Si)2NK to the alkoxide 4 produces the amide catalytic intermediate 5. Compound 5 reacts reversibly with H2 to generate 3'.
二氢化合物反式-[Ru((R)-联萘二苯膦)(H)(η²-H₂)((R,R)-二苯乙二胺)]⁺ (2'，联萘二苯膦 = 2,2'-双(二苯基膦基)-1,1'-联萘，二苯乙二胺 = 1,2-二苯基乙二胺) 是不对称酮氢化反应中提出的中间体。在-80℃下，它在H₂气氛中于2-丙醇-d₈/二氯甲烷-d₂中与1当量的碱叔丁醇钾迅速反应，生成反式-Ru((R)-联萘二苯膦)(H)(2-丙氧基)((R,R)-二苯乙二胺) (4)。在环境条件下，数小时后醇盐4不与H₂反应。向4中加入1当量的叔丁醇钾会产生一种氢键物种10，其在-80℃下很容易与H₂反应生成二氢催化中间体反式-[Ru((R)-联萘二苯膦)(H)₂((R,R)-二苯乙二胺)] (3')。向醇盐4中加入1当量的双(三甲基硅基)氨基钾会生成酰胺催化中间体5。化合物5与H₂可逆反应生成3'。
Zotero 插件