Transition Metal-Catalyzed [5 + 2] Cycloadditions of 2-Substituted-1-vinylcyclopropanes: Catalyst Control and Reversal of Regioselectivity
摘要:
[GRAPHICS]Studies on the stereo- and regioselectivity of rhodium(I) catalyzed [5 + 2] cycloadditions of 2-substituted-1-vinylcyclopropanes are described. The relative stereochemistry of vicinal cyclopropane substituents is found to be conserved in these reactions, translating into distinct 1,4- or 1,5-stereorelationships in the cycloadducts. Exceptional regioselectivity in cyclopropane bond cleavage and even reversal of cleavage selectivity can be obtained through judicious selection of substituents and/or catalyst.
On the Regioselectivity of the Ru-Catalyzed Intramolecular [5 + 2] Cycloaddition
作者:Barry M. Trost、Hong C. Shen
DOI:10.1021/ol0061945
日期:2000.8.1
[GRAPHICS]The influence of substituents on which cyclopropyl bond cleaves in the cycloisomerization of cyclopropylenynes catalyzed by CpRu(N=CCH3)(3)PF6- is compared to the corresponding Rh-catalyzed reaction. With the trans cyclopropyl substrates, the bond energy of the cleaving bond appears to be an important factor. With cis cyclopropyl substrates, steric effects appear to dominate.