5 years ago

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

Ruthenium-Catalyzed Site-Selective Intramolecular Silylation of Primary C–H Bonds for Synthesis of Sila-Heterocycles
Wenjun Hou, Zheng Huang, Guixia Liu, Huaquan Fang
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.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b06798

DOI: 10.1021/jacs.7b06798

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