DI-TERT-BUTYLSILYL BIS(TRIFLUOROMETHANESULFONATE)

Colorless to yellow liquid

bp 73–75°C/0.35 mmHg; d 1.208 g cm?3.

Protecting group reagent for 1,3-diols used recently in a synthesis of N-homoceramides. Also used for selective α-galactosylation in the synthesis of α-galactosyl ceramides.

Di-t-butylsilyl bis(trifluoromethanesulfonate) is a reagent for the selective protection of polyhydroxy compounds. This reagent reacts with 1,2-, 1,3-, and 1,4-diols under mild conditions to give the corresponding dialkylsilylene derivatives in high yield (0–50°C, 79–96%). Deprotection is conveniently achieved by using aqueous hydrofluoric acid in acetonitrile (eq 1).
Unlike di-t-butyldichlorosilane, this reagent reacts with hindered alcohols. Even pinacol reacts to give the silylene derivative (100°C, 24 h, 70%). Di-t-butylsilylene derivatives of 1,2-diols are more reactive than those of 1,3- and 1,4-diols and undergo rapid hydrolysis (5 min) in THF/H2O at pH 10, while the 1,3- and 1,4- derivatives are unaffected at pH 4–10 (22°C) for several hours. This protecting group is stable under the conditions of PDC oxidation of alcohols (CH2Cl2, 25?C, 27 h) and tosylation of alcohols (pyridine, 25°C, 27 h).
The reagent has seen limited use for the protection of alcohols but has been used to protect nucleosides (eq 2).The procedure consists of sequential addition of the ditriflate and triethylamine to the nucleoside in DMF. The choice of solvent is critical.

by the treatment of di-t-butylchlorosilane with trifluoromethanesulfonic acid, followed by distillation (71% yield).