Stereoselective Synthesis of Cis- and Trans-Tetrasubstituted Vinyl Silanes Using a Silyl-Heck Strategy and Hiyama Conditions for Their Cross-Coupling.

We report a palladium-catalyzed, three-component carbosilylation reaction of internal symmetrical alkynes, silicon electrophiles, and primary alkyl zinc iodides. Depending on the choice of ligand, stereoselective synthesis of either cis- or trans-tetrasubstituted vinyl silanes is possible. We also demonstrate conditions for the Hiyama cross-coupling of these products to prepare geometrically defined tetrasubstituted alkenes.

Palladium-Catalyzed Cross-Coupling of Silyl Electrophiles with Alkylzinc Halides: A Silyl-Negishi Reaction.

We report the first example of a silyl-Negishi reaction between secondary zinc organometallics and silicon electrophiles. This palladium-catalyzed process provides direct access to alkyl silanes. The delicate balance of steric and electronic parameters of the employed DrewPhos ligand is paramount to suppressing isomerization and promoting efficient and selective cross-coupling.

Palladium-Catalyzed Cross-Coupling of Monochlorosilanes And Grignard Reagents.

Using a palladium catalyst supported by DrewPhos, the alkylation of monochlorosilanes with primary and secondary alkyl-magnesium halides is now possible. Arylation with sterically demanding aromatic magnesium halides is also enabled. This transformation overcomes the high bond strength of the Si-Cl bond (113 kcal/mol) and is a rare example of a transition-metal catalyzed process involving its activation. Due to the availability of both chlorosilanes and organomagnesium halide reagents, this method allows for the preparation of a wide range of alkyl and aryl silanes.

The First Example of Nickel-Catalyzed Silyl-Heck Reactions: Direct Activation of Silyl Triflates Without Iodide Additives.

For the first time, nickel-catalyzed silyl-Heck reactions are reported. Using simple phosphine-supported nickel catalysts, direct activation of silyl triflates has been achieved. These results contrast earlier palladium-catalyzed systems, which require iodide additives to activate silyl-triflates. These nickel-based catalysts exhibit good functional group tolerance in the preparation of vinyl silanes, and unlike earlier systems, allows for the incorporation of trialkylsilanes larger than Me3Si.

General route for preparing ß-nitrocarbonyl compounds using copper thermal redox catalysis.

Using a simple copper catalyst, the alkylation of nitroalkanes with α-bromocarbonyls is now possible. This method provides a general, functional group tolerant route to ß-nitrocarbonyl compounds, including nitro amides, esters, ketones, and aldehydes. The highly sterically dense, functional group rich products from these reactions can be readily elaborated into a range of complex nitrogen-containing molecules, including highly substituted ß-amino acids.