Mazzola Robert D, White Timothy D, Vollmer-Snarr Heidi R, West F G
Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, USA.
Org Lett. 2005 Jun 23;7(13):2799-801. doi: 10.1021/ol051169q.
[reaction: see text] Bridged bicyclic dienones underwent silyl-directed Nazarov cyclization with generally very high diastereoselectivity. In most cases, a strong preference for cyclization to the product with an exo-disposed cyclopentenone was seen. However, the presence of additional unsaturation in the three-carbon bridge of a bicyclo[3.2.1]octadiene system caused complete reversal in selectivity with exclusive formation of the endo-cyclopentenone. The observed selectivities are believed to result from a combination of steric and electronic effects.
[反应：见正文] 桥连双环二烯酮进行硅基导向的纳扎罗夫环化反应时，通常具有非常高的非对映选择性。在大多数情况下，观察到强烈倾向于环化生成具有外型环戊烯酮的产物。然而，双环[3.2.1]辛二烯体系的三碳桥中存在额外的不饱和键，导致选择性完全反转，专一性生成内型环戊烯酮。据信，观察到的选择性是由空间效应和电子效应共同作用的结果。
