Ruthenium-Catalyzed Site-Selective Intramolecular Silylation of Primary C–H Bonds for Synthesis of Sila-Heterocycles

Incorporating the silicon element into bioactive organic molecules has received increasing attention in medicinal chemistry. Moreover, organosilanes are valuable synthetic intermediates for fine chemicals and materials. Transition metal-catalyzed C–H silylation has become an important strategy for C–Si bond formations. However, despite the great advances in aromatic C­(sp²)–H bond silylations, catalytic methods for aliphatic C­(sp³)–H bond silylations are relatively rare. Here we report a pincer ruthenium catalyst for intramolecular silylations of various primary C­(sp³)–H bonds adjacent to heteroatoms (O, N, Si, Ge), including the first intramolecular silylations of C–H bonds α to O, N, and Ge. This method provides a general, synthetically efficient approach to novel classes of Si-containing five-membered [1,3]-sila-heterocycles, including oxasilolanes, azasilolanes, disila-heterocycles, and germasilolane. The trend in the reactivity of five classes of C­(sp³)–H bonds toward the Ru-catalyzed silylation is elucidated. Mechanistic studies indicate that the rate-determining step is the C–H bond cleavage involving a ruthenium silyl complex as the key intermediate, while a η²-silene ruthenium hydride species is determined to be an off-cycle intermediate

Synthesis of Pincer Hydrido Ruthenium Olefin Complexes for Catalytic Alkane Dehydrogenation

A series of new hydrido Ru­(II) olefin complexes supported by isopropyl-substituted pincer ligands have been synthesized and characterized. These complexes are thermally robust and active for catalytic transfer and acceptorless alkane dehydrogenation. Notably, the alkane dehydrogenation catalysts are tolerant of a number of polar functional species

Cobalt-Catalyzed Borylation of Aryl Halides and Pseudohalides

We report the first Co-catalyzed borylation of aryl halides and pseudohalides with bis­(pinacolato)­diboron (B₂pin₂). The synthesis of two new Co­(II) complexes of oxazolinylferrocenylphosphine ligands is described. Upon activation with LiMe, the Co complex catalyzes the borylation reactions of aryl bromides, iodides, sulfonates, arenediazonium salts, and even aryl chlorides under mild conditions, providing the borylated products in excellent to moderate yields and with high functional group tolerance