DiRocco Daniel A, Oberg Kevin M, Dalton Derek M, Rovis Tomislav
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
J Am Chem Soc. 2009 Aug 12;131(31):10872-4. doi: 10.1021/ja904375q.
The catalytic asymmetric intermolecular Stetter reaction of heterocyclic aldehydes and nitroalkenes has been developed. We have identified a strong stereoelectronic effect on catalyst structure when a fluorine substituent is placed in the backbone. X-ray structure analysis provides evidence that hyperconjugative effects are responsible for a change in conformation in the azolium precatalyst. This new N-heterocyclic carbene precursor bearing fluorine substitution in the backbone results in significantly improved enantioselectivities across a range of substrates.
已开发出杂环醛与硝基烯烃的催化不对称分子间施陶丁格反应。我们发现，当在主链中引入氟取代基时，对催化剂结构存在强烈的立体电子效应。X射线结构分析提供了证据，表明超共轭效应是导致唑鎓预催化剂构象变化的原因。这种在主链中带有氟取代基的新型N-杂环卡宾前体，可显著提高一系列底物的对映选择性。
