In the presence of 20 mol% of a chiral (acyloxy)borane (CAB) complex prepared from BH3·THF and a chiral mono-O-acylated tartaric acid, achiral silyl enol ethers or ketenesilylacetals react with achiral aldehydes to afford the corresponding aldol-type adducts in good yields with high enantio- and diastereoselectivities. Furthermore, the reactivity of aldol-type reactions can be improved without reducing
The Chemistry of Trichlorosilyl Enolates. Aldol Addition Reactions of Methyl Ketones
作者:Scott E. Denmark、Robert A. Stavenger
DOI:10.1021/ja001023g
日期:2000.9.1
observed in this uncatalyzed aldol process. The aldol additions are dramatically accelerated by the addition of catalytic quantities of chiral phosphoramides, particularly one derived from N,N‘-dimethylstilbene-1,2-diamine. In this catalyzed mode, good to high enantioselectivities are obtained with a variety of achiral trichlorosilyl enolates and aldehydes. When either partner bears a stereogenic center
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。
Enantioselective Mukaiyama-aldol and aldol-dihydropyrone annulation reactions catalyzed by a tryptophan-derived oxazaborolidine
作者:E.J. Corey、Charles L. Cywin、Thomas D. Roper
DOI:10.1016/s0040-4039(00)60892-4
日期:1992.11
The (S)-tryptophan derived catalyst 1, has been used to effect enantioselective Mukaiyama-aldol and aldol-dihydropyrone annulation reactions of trimethylsilyloxy olefins and, dienes.
Oxazaborolidin-5-one, von Tryptophan abgeleitete chirale Lewis-Säre-Reagentien zur asymmetrischen Katalyse