Trifluoromethyltrimethylsilane

Trifluoromethyltrimethylsilane (TMSCF₃) is a fluorinated derivative of tetramethylsilane (TMS), the Molecule of the Week for March 29, 2021. Like TMS, TMSCF₃ is a volatile liquid; but the fluorinated compound is considerably more reactive and hazardous.

TMSCF₃ is not synthesized from TMS; rather, it is formed by coupling molecules containing trifluoromethyl and trimethylsilyl groups. The initial synthesis, by Ingo Ruppert*, Klaus Schlich, and Wolfgang Volbach at the University of Bonn (Germany) in 1984, involved the reaction of bromotrifluoromethane (CBrF₃) and trimethylsilyl chloride (TMSCl) in the presence of an amine–phosphorus catalyst.

Similar methods followed over the next several years, culminating in one reported by G. K. Surya Prakash*, Ramesh Krishnamurti, and George A. Olah*¹ at the University of Southern California (Los Angeles) in 1989 that does not require ozone-depleting reagents such as CBrF₃. Instead, the researchers treated fluoroform (CHF₃) with TMSCl and the base potassium hexamethyldisilazide to obtain TMSCF₃ in 80% isolated yield.

Ruppert and Prakash prepared TMSCF₃ because they had bigger things in mind. Specifically, they sought to introduce a reagent that could easily add the trifluoromethyl group to a wide range of organic substrates. Now known as the Ruppert–Prakash reagent, TMSCF₃ has been used to add CF₃ or the difluoromethylene group to aldehydes, ketones, olefins, alkynes, heterocyclic systems, and more.

In 2014, Mang Wang, Qun Liu, and colleagues at Northeast Normal University (Changchun, China) published an excellent review of TMSCF₃ chemistry. So much work is being done with TMSCF₃ that, even after the conclusion of the review, the authors felt compelled to add an additional section that reported findings that appeared after the original manuscript was submitted for publication.

1. Olah received the Nobel Prize in Chemistry in 1994 for his work on superacids and carbocations.