Chiral 2-<i>endo</i>-Substituted 9-Oxabispidines: Novel Ligands for Enantioselective Copper(II)-Catalyzed Henry Reactions
作者:Matthias Breuning、David Hein、Melanie Steiner、Viktoriaâ
H. Gessner、Carsten Strohmann
DOI:10.1002/chem.200901789
日期:2009.11.23
The CuCl2 complex of the tricyclic 9‐oxabispidine, which carries an 2‐endo,N‐anellated piperidine ring, is an excellent catalyst for enantioselective Henry reactions giving the S‐configured β‐nitro alcohols in 91–98 % ee (13 examples). Surprisingly, the analogous copper complexes of the bicyclic 9‐oxabispidines delivered the enantiocomplementary R‐configured products in 33–57 % ee. The respective transition
开发了一种适用于克级的灵活方法,用于手性2-内基取代的9-氧杂哌啶。关键中间体是顺式构型的6-氨基甲基吗啉-2-腈,是由(R)-3-氨基丙烷-1,2-二醇和2-氯丙烯腈制得的。2-内型取代基是由Grignard加成,环化,并引入外切体选择性还原,从而家具在19-59%的产率的对映体纯二和三环9- oxabispidines。氯化亚铜2复合物中的三环9 oxabispidine的,其携带一个2-内型,N-稠合哌啶环,是对映选择性亨利反应给出一种极好的催化剂小号在91–98%ee中配置的β-硝基醇 (13个示例)。出人意料的是,双环9-氧杂萘啶类似的铜络合物以33–57 %ee的浓度提供了对映体互补的R构型产物 。讨论了各自的过渡状态。