Strong electronic effects in the cis-selective asymmetric cyclopropanationof olefins catalyzed by [RuCl(PNNP)](+)

The cationic [RuCl(PNNP)](+) catalysts containing tetradentate ligands with a P2N2 donor set (PNNP) show strong electronic effects in the cyclopropana tion of para-substituted styrenes. The reactivity trend confirms that the c arbene transfer to the olefin has electrophilic character. Linear free-ener gy relationships are observed for the relative reactivity, the cis/trans se lectivity, and for the enantioselectivity (of the cis-cyclopropane). The li near correlation between log (k(X)/k(H)) and sigma shows a large value of r ho (-2.4), which is indicative of significant charge buildup in the transit ion state of the carbene transfer to the olefin. All the relevant parameter s (reactivity, diastereoselectivity, and enantioselectivity) increase with the increasing electron density at the C=C bond. To define the scope of the [RuCl(PNNP)](+) catalysts, 1- and 2-substituted styrenes, and oct-1-ene we re also investigated.