已经开发了带有L-脯氨酸衍生的N 4配体的新型锰催化剂,其能够使用叔丁基氢过氧化物作为氧化剂实现烯烃的无酸不对称环氧化。大小与配位体袋完全匹配的各种烯烃可以转化为具有出色对映选择性的环氧化物。较小的配体口袋也有利于简单烯烃的对映选择性环氧化。低温喷雾电离质谱实验表明,Mn IV O物种可作为活性环氧化物种。
Highly Enantioselective Synthesis of Glycidic Amides Using Camphor-Derived Sulfonium Salts. Mechanism and Applications in Synthesis
作者:Varinder K. Aggarwal、Jonathan P. H. Charmant、Daniel Fuentes、Jeremy N. Harvey、George Hynd、Diasuke Ohara、Willy Picoul、Raphaël Robiette、Catherine Smith、Jean-Luc Vasse、Caroline L. Winn
DOI:10.1021/ja0568345
日期:2006.2.1
amide-stabilized sulfur ylides derived from readily available camphor-derived sulfonium salts for the synthesis of glycidic amides have been studied. Primary, secondary, and tertiaryamides were tested, and it was found that the highest enantioselectivities were observed with tertiaryamides, which provided glycidic amides in good to excellent yields, exclusive trans selectivity, and excellent enantioselectivities
carbonyl‐stabilised ammoniumylide‐mediated epoxidation reactions were systematically investigated by experimental and computational means and the hereby obtained energy profiles provide explanations for the observed experimental results. In addition, we were able to identify the first tertiary amine‐based chiral auxiliary that allows for high enantioselectivities and high yields for such epoxidation reactions.
Enantiomerically enriched trans-2,3-epoxyamides 3 were prepared by the reaction of aldehydes 2 with camphor-derived chiral sulfoniumylide 1 in good yields and moderate to good ee values. The absolute configuration of the reaction product is also determined by chemical transformations.
Highly Enantioselective Darzens Reaction of a Camphor-Derived Sulfonium Amide to Give Glycidic Amides and Their Applications in Synthesis
作者:Varinder K. Aggarwal、George Hynd、Willy Picoul、Jean-Luc Vasse
DOI:10.1021/ja0272540
日期:2002.8.1
sulfonium ylide bearing chiral groups on sulfur has been investigated. We have discovered that the camphor-derived amide-stabilized ylide reacts with aldehydes at -50 degrees C in ethanol to give glycidic amides in one step with up to 99% ee and complete diastereoselectivity. From analyzing reactions of different ratios of diastereomers at sulfur it was found that the major diastereomer gave very high