Asymmetric Counteranion-Directed Transition-Metal Catalysis: Enantioselective Epoxidation of Alkenes with Manganese(III) Salen Phosphate Complexes
作者:Saihu Liao、Benjamin List
DOI:10.1002/anie.200905332
日期:2010.1.12
Paired up: A highly active and enantioselective ion‐pair epoxidationcatalyst, consisting of an achiral MnIII–salen complex and a chiral phosphate counteranion, mediates the epoxidization of a wide range of alkenes with high yields and enantioselectivities (see scheme). The unique role of the counteranion is to stabilize an enantiomorphic conformation of the cationic Mn catalyst.
配对:高活性和对映选择性离子对环氧化催化剂,由非手性Mn III -salen配合物和手性磷酸抗衡阴离子组成,可介导高产率和对映选择性的多种烯烃的环氧化。抗衡阴离子的独特作用是稳定阳离子Mn催化剂的对映体构象。
New mannose-derived ketones as organocatalysts for enantioselective dioxirane-mediated epoxidation of arylalkenes. Part 3: Chiral ketones from sugars
作者:José M. Vega-Pérez、Ignacio Periñán、Margarita Vega-Holm、Carlos Palo-Nieto、Fernando Iglesias-Guerra
DOI:10.1016/j.tet.2011.07.014
日期:2011.9
New D-arabino-hexopyranosid-3-uloses were synthesized by a simple method from mannopyranoside derivatives. The common skeleton possesses a tunable alkoxy group as steric sensor on carbon 2 of the sugar. The new ketones were employed in the dioxirane-mediated epoxidation of a range of trans- and trisubstituted arylalkenes giving enantiomeric excesses from low to good (30-90%). The effect of the size of the steric sensor on the enantioselectivity was also studied. The least bulky group (methoxy group) enhanced the stereoselectivity (up to 90% ee toward triphenylethylene). (C) 2011 Elsevier Ltd. All rights reserved.