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).
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。
Chiral Phosphoramide-Catalyzed Aldol Additions of Ketone Enolates. Preparative Aspects
作者:Scott E. Denmark、Robert A. Stavenger、Ken-Tsung Wong、Xiping Su
DOI:10.1021/ja984123j
日期:1999.6.1
Trichlorosilyl enolates of ketones (enoxytrichlorosilanes) were demonstrated to be highly reactive aldoladdition reagents. Trichlorosilyl enolates of cyclohexanone (E-enolate) and propiophenone (Z-enolate) reacted readily at room temperature with a wide variety of aldehydes to afford aldoladdition products in high yield and diastereoselectivity (E → syn, Z → anti). These reactions were shown to be
Stereoselective Aldol Additions of Achiral Ethyl Ketone-Derived Trichlorosilyl Enolates
作者:Scott E. Denmark、Son M. Pham
DOI:10.1021/jo034092x
日期:2003.6.1
ethyl ketoneenolates have been developed. The addition of enoxy(trichlorosilanes) (trichlorosilylenolates) to aldehydes proceeds with good yields in the presence of catalytic amounts of chiral phosphoramides. The reaction of Z-trichlorosilyl enolates to aryl aldehydes affords aldol products with good to excellent diastereo- and enantioselectivities. Phosphoramide-catalyzed aldoladditions lacked