On the regioselectivity of the Ru-catalyzed intramolecular [5+2] cycloaddition

[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.