SiMe2tBu

SiMe2tBu, commonly abbreviated TBDMS or TBS, refers to the tert-butyldimethylsilyl substituent used as a protecting group in organic synthesis. The group consists of a silicon atom bound to two methyl groups and a tert-butyl group. When installed on an alcohol, it forms a tert-butyldimethylsilyl ether (RO–SiMe2tBu), effectively protecting the hydroxyl functionality during subsequent reactions.

Installation and removal

Protected alcohols are typically prepared by treating the alcohol with tert-butyldimethylsilyl chloride (TBDMS–Cl) or TBDMS triflate in the presence of a base such as imidazole, diisopropylethylamine, or 2,6-lutidine. TBDMS ethers are valued for their balance of stability and ease of removal: they resist many acidic and basic conditions but can be deprotected selectively with fluoride sources such as tetrabutylammonium fluoride (TBAF) or HF–pyridine, reverting to the free alcohol.

Comparison and scope

Compared with the smaller trimethylsilyl (TMS) group, TBDMS offers greater stability under a wider range of conditions. It is generally less tolerant of very strong acids or aggressive fluoride reagents than even more robust silyl groups like TIPS or TBDPS, but remains a standard choice for protecting alcohols in complex, multi-step syntheses. Related reagents include TBDMS–Cl and TBDMS–OTf, used to install the group under various conditions.

See also

Silyl protecting groups; TBDMSCl; TBS.