Trimethylsilyl trifluoromethanesulfonate

Trimethylsilyl trifluoromethanesulfonate (TMSOTf) is an organosilicon compound with the formula (CH3)3SiO3SCF3. It is a colorless moisture-sensitive liquid. It is the trifluoromethanesulfonate derivative of trimethylsilyl. It is mainly used to activate ketones and aldehydes in organic synthesis.

Reactions
TMSOTf is quite sensitive toward hydrolysis:
 * (CH3)3SiO3SCF3 + H2O  ->  (CH3)3SiOH  +  HO3SCF3

It is far more electrophilic than trimethylsilyl chloride.

Related to its tendency to hydrolyze, TMSOTf is effective for silylation of alcohols:
 * (CH3)3SiO3SCF3 + ROH  +  Et3N  ->  ROSi(CH3)3Si  +  [Et3NH]O3SCF3

A common use of (CH3)3SiO3SCF3 is for the preparation of silyl enol ethers. One example involves the synthesis of the silyl enol ether of camphor:


 * Tms enol ether formation.svg

It was also used in Takahashi Taxol total synthesis and in chemical glycosylation reactions.

Trimethylsilyl trifluoromethanesulfonate has a variety of other specialized uses. It has been used to install tert-alkyl groups on phosphine (R = alkyl):


 * PH3 +  R3C–OAc  +  Me3SiOTf  →  [(R3C)2PH2]OTf

Deprotection of Boc-protected amines can be achieved using trimethylsilyl trifluoromethanesulfonate and triethylamine or 2,6-lutidine.

TMSOTf is also a useful reagent to replace metal-halogen bonds with a covalent M-O(SO2CF3) bond, the by-product being the highly volatile TMSCl which is easily removed.