silylation

Silylation is a chemical transformation in which a silyl group (SiR3) is introduced into a molecule. In organic synthesis it most often refers to the installation of silyl protecting groups on heteroatoms such as oxygen or nitrogen to mask reactivity, but it also encompasses formation of carbon–silicon bonds by hydrosilylation or direct C–H silylation and, in materials chemistry, surface silanization.

The most widely used protecting groups for alcohols and, less commonly, amines are trimethylsilyl (TMS), tert-butyldimethylsilyl (TBS), triethylsilyl (TES), and tert-butyldiphenylsilyl (TBDPS). Silyl groups are typically introduced with silyl chlorides or triflates (for example TMSCl, TBSCl, TESCl, TBDPSCl) in the presence of a base such as imidazole, DIPEA or DMAP, in solvents like dichloromethane or acetonitrile. For more robust protection, fluoride-promoted conditions or reagents such as hexamethyldisilazane (HMDS) may be used. Deprotection commonly employs fluoride sources (tetrabutylammonium fluoride, TBAF) or, for acid-sensitive groups, acidic conditions.

Beyond protection, silylation encompasses C–Si bond formation via hydrosilylation, where Si–H adds across C=C or C≡C bonds under transition-metal catalysis, enabling installation of silyl substituents on hydrocarbons. Surface silylation uses silane coupling agents to graft Si–O– or Si–C–R linkages onto oxide or metal surfaces to modify wettability, adhesion, or biocompatibility.