[85272-30-6] · C8H14F6O6S2Si · Diisopropylsilyl Bis(trifluoromethanesulfonate) · (MW 412.39)
(bifunctional silyl protecting group for 1,2-, 1,3-, and 1,4-diols)
Physical Data: bp 85-86 °C/2 mmHg; d 1.396 g cm-3; fp 110 °C.
Preparative Method: conveniently prepared by the slow addition of 2 equiv of Trifluoromethanesulfonic Acid to a stirring mixture of Chlorodiisopropylsilane, followed by direct distillation of the product from the reaction flask to yield the product as a pale yellow oil.1
Handling, Storage, and Precautions: store in the refrigerator under an inert atmosphere of argon or nitrogen. Special care should be used when handling since diisopropysilyl bis(trifluoromethanesulfonate) has been classified as a corrosive.
The use of silyl protecting groups in organic synthesis has been limited to monofunctional silicon compounds. Their use has been enhanced by the fact that they may be put on and removed under mild conditions. Diisopropylsilyl bis(trifluoromethanesulfonate) and its analog, Di-t-butylsilyl Bis(trifluoromethanesulfonate), go one step further in protecting group technology. The two electrophilic sites on silicon allow for the simultaneous protection of 1,2-, 1,3-, and 1,4-diols, and in some cases form a rigid system which allows for asymmetric stereocontrol in subsequent organic transformations.1
Polyfunctional silicon protecting groups have been employed by researchers before the use of silicon ditriflates. Trost and co-workers found in the development of methodology towards the synthesis of erythronolide A that Di-t-butyldichlorosilane was relatively unreactive under standard silylation conditions and required forcing conditions (65-95 °C, 1-Hydroxybenzotriazole, MeCN, or DMF) for its employment.2 These two factors make dichlorosilanes limited in their applicability. Silicon ditriflates will react readily with many diols in the presence of 3 equiv of 2,6-Lutidine in chloroform at temperatures ranging from 0-25 °C. The generality of this polyfunctional protecting group is illustrated by the formation of the silyl-protected diols (1), (2), and (3).
Corey and Link utilized diisopropylsilyl bis(trifluoromethanesulfonate) as a silylating agent for catechols in the first enantioselective synthesis of pure (R)- or (S)-isoproterenol (eq 1).3
Janet Wisniewski Grissom
University of Utah, Salt Lake City, UT, USA