Palladium-Catalyzed Hydrosilylation of Unactivated Alkenes and Conjugated Dienes with Tertiary Silanes Controlled by Hemilabile Hybrid P,O Ligand.

Novel P,O-type ligands, N-disulfonyl bicyclic bridgehead phosphorus triamides, were synthesized and utilized in Pd-catalyzed hydrosilylation involving tertiary silanes, unactivated alkenes, and conjugated dienes. The ligand displayed a remarkable level of reactivity for alkene hydrosilylation with tertiary silanes and its use resulted in a significant improvement in the regioselectivity of diene hydrosilylation towards 1,2-hydrosilylation. X-ray crystallographic analysis confirmed the bidentate nature of the ligand, with coordination of phosphorus and oxygen. Control experiments provided evidence for the formation of Pd0 species and the reversibility of Pd-H insertion in the reaction mechanism. Density functional theory (DFT) computations supported the importance of the hemilabile P,O ligand in stabilizing both the rate-determining transition state of Pd-H insertion and the transition state of reductive elimination that determines the regioselectivity.

Hydrophilic Catalysts with High Activity and Stability in the Aqueous Polymerization of Ethylene to High-Molecular-Weight-Polyethylene.

Water-soluble synthetic transition metal catalysts have been studied extensively for many reactions, but for olefin polymerization such catalysts have been lacking. We report herein a straightforward synthesis of phosphinephenolato NiII catalysts endowed permanently with a hydrophilic sulfonate moiety bound to the chelating ligand. These catalysts' hydrophilic active sites promote aqueous ethylene polymerization with high activity (TOF up to 6.3×104  molEthylene molNi -1 h-1 ) to high molecular weight polyethylene (HDPE), with half-lives on the order of hours also at elevated temperatures. The obtained polyethylene dispersions feature narrow particle size distributions without any aggregates.

Diastereo- and Enantioselective Copper(I)-Catalyzed Intermolecular [3+2] Cycloaddition of Azomethine Ylides with ß-Trifluoromethyl ß,ß-Disubstituted Enones.

Reported herein is an asymmetric [3+2] cycloaddition reaction of azomethine ylides with ß-trifluoromethyl ß,ß-disubstituted enones, a reaction which is enabled by a Ming-Phos-derived copper(I) catalyst (Ming-Phos=chiral sulfinamide monophosphines, Figure ). This method provides scalable and efficient access to the highly substituted pyrrolidines with a trifluoromethylated, all-carbon quaternary stereocenter in good yields with up to greater than 20:1 d.r. and 98 % ee. The reaction has a broad substrate scope and tolerates a wide range of functional groups.