Metallopalladation

Highly Diastereo- and Regioselective Transition Metal-Catalyzed Additions of Metal Hydrides and Bimetallic Species to Cyclopropenes: Easy Access to Multisubstituted Cyclopropanes

“…While the insertion into a more electrophilic Pd−Sn bond is usually preferred, , there is a number of literature examples of selective transformations proceeding via the palladasilylation pathway . Furthermore, theoretical computations on the silastannation of alkynes suggest that, in the absence of strong steric effects, addition of the palladium moiety to a more substituted carbon atom is electronically more favorable 34 the effect also is observed in numerous other reactions involving olefin insertion into various Pd−X bonds. , However, increasing the steric bulk on Pd can reverse the addition aptitude, resulting in the addition of palladium to the least hindered site (Scheme ). ,, In view of that, the observed regioselectivity trend in the silastannation of cyclopropenes (Table ), with regards to the size of the isocyanide ligand and the relative sizes of the Sn and Si moieties in the silastannane reagents, is in better agreement with the palladastannation rather than the palladasilylation pathway for the following reasons.…”

Palladium-Catalyzed Dimerization Disilylation of 1,3-Butadiene with Chlorosilanes

“…Among a variety of methods having been developed for such transformations, transition metal-catalyzed silylation provides useful routes to organosilanes from carbon−carbon unsaturated compounds. In these reactions various silylating reagents possessing silicon−hydrogen, silicon−silicon, or silicon−heteroatom bonds 2b have been employed; however, chlorosilanes (R 3 SiCl) have rarely been employed in transition metal-catalyzed C−Si bond-forming reactions probably due to the difficulty of the oxidative addition of the Si−Cl bond to low-valent metal complexes . During the course of our project on the synthetic use of chlorosilanes in transition metal-catalyzed reactions, we have reported unique silylation reactions of olefins and dienes with chlorosilanes by the combined use of Grignard reagents and early transition metal catalysts such as Cp 2 ZrCl 2 or Cp 2 TiCl 2 .…”