由手性膦BINAP容易制备的手性膦氧化物BINAPO在三氯甲硅烷基化合物通过高价硅酸盐中间体的反应中表现出良好的催化活性。在催化量的BINAPO存在下,醛与烯丙基三氯硅烷的烯丙基化反应使烯丙基化的加合物具有良好的对映选择性(最高79%ee),其中二异丙基乙胺和四丁基碘化铵作为添加剂的组合对于加速催化循环至关重要。31氧化膦的1 P NMR分析表明,胺促进了氧化膦从硅原子上的解离。BINAPO还促进了二异丙基乙胺作为添加剂存在下醛与三氯甲硅烷基烯醇醚的对映体选择性醛醇缩合反应,从而以高非对映体和对映体选择性(最高syn / anti = 1 / 25,96%ee(anti))提供了相应的醛醇加合物。)。
Chiral phosphine oxide successfully catalyzed the direct aldol-type reactions of cyclohexanone derivatives and benzaldehyde derivatives in high stereoselectivities. The reaction mechanism involves the in situ formation of trichlorosilyl enol ethers. The present reaction could be extended to the cross-aldolreactionsbetween two aldehydes.
The Chemistry of Trichlorosilyl Enolates. 2. Highly-Selective Asymmetric Aldol Additions of Ketone Enolates
作者:Scott E. Denmark、Ken-Tsung Wong、Robert A. Stavenger
DOI:10.1021/ja9636698
日期:1997.3.1
problem, namely, the invention/discovery of asuitable chiral Lewis acid catalyst to effect the reaction betweenan enoxysilane derivative and an aldehyde, Scheme 1 (X ) Me).In a recent Communication we have described a conceptuallydistinct approach which employs chiral Lewis bases (phos-phoramides) in combination with trichlorosilyl enolates, Scheme1(X)Cl).
The enantioselective aldol reactions of aldehydes with trichlorosilyl enol ethers catalyzed by chiral phosphine oxide BINAPO afforded the corresponding aldol adducts with high diastereo- and enantioselectivities.
Chiral Phosphoramide-Catalyzed Aldol Additions of Ketone Trichlorosilyl Enolates. Mechanistic Aspects
作者:Scott E. Denmark、Son M. Pham、Robert A. Stavenger、Xiping Su、Ken-Tsung Wong、Yutaka Nishigaichi
DOI:10.1021/jo060243v
日期:2006.5.1
mechanism of the catalytic, enantioselective addition of trichlorosilylenolates to aldehydes has been investigated. Kinetic studies using ReactIR and rapid injection NMR (RINMR) spectroscopy have confirmed the simultaneous operation of dualmechanistic pathways involving either one or two phosphoramides bound to a siliconium ion organizational center. This mechanistic dichotomy was initially postulated on
已经研究了将三氯甲硅烷基烯酸酯催化,对映选择性加成到醛的机理。使用ReactIR和快速注入NMR(RINMR)光谱进行的动力学研究已证实,涉及一个或两个与硅离子组织中心结合的磷酰胺的双机理途径的同时运行。最初基于催化剂负载量研究和非线性效应研究假定了这种机械二分法。这种二元性解释了各种类型的磷酰胺的反应性和立体选择性的差异。Arrhenius激活参数的确定表明,醛醇的添加是通过可逆的方式发生的,尽管不利的是形成了活化的复合物,并且自然丰度1313 C NMR动力学同位素效应(KIE)研究已经确定,周转限制步骤是添加羟醛。对一系列磷酰胺的彻底检查已经建立了经验结构-活性选择性关系。此外,已经研究了催化剂负载量,添加速率,溶剂和添加剂的影响,这些影响共同形成了醇醛添加的统一机理图。
Chemistry of Trichlorosilyl Enolates. 1. New Reagents for Catalytic, Asymmetric Aldol Additions
作者:Scott E. Denmark、Stephen B. D. Winter、Xiping Su、Ken-Tsung Wong
DOI:10.1021/ja9606539
日期:1996.1.1
The asymmetric aldol addition is among the most powerful reactions in synthetic organic chemistry and has been extensively studied over the past 15 years.1 The strategies for reagentcontrolled asymmetricinduction fall into three broadly defined classes (Chart 1): (1) asymmetric modification of the enolate with chiral acyl auxiliaries (A), (2) asymmetric modification of the enolate with chiral metalloid