Date of Award
Doctor of Philosophy (PhD)
Joseph S. Thrasher, Ph.D., Committee Chair
Stephen E. Creager, Ph.D.
Shiou-Jyu Hwu, Ph.D.
William T. Pennington, Ph.D.
Fluorinated organic compounds have received great attention and even play a key role in human daily life. Now up to 30% of agrochemicals and 20% of all pharmaceuticals contain one or more fluorine atoms. The development of more atom-economic efficiency and green procedures for the introduction of fluorine atoms and fluorine-containing groups into organic molecules has gained increasing interest lately. The focus of this work is to introduce the highly electronegative and lipophilic trifluoromethyl (CF3-) and pentafluorosulfanyl groups (SF5-) into organic substrates. New and convenient routes for the preparation of the widely used trifluoromethylation reagents trifluoromethyltrimethylsilane (TMSCF3) and potassium (trifluoromethyl)trimethoxyborate [CF3B(OMe)3-K+] using fluoroform (CF3H) as the trifluoromethyl source were successfully developed. Dimsyl-K, freshly prepared from potassium hydride (KH) and dimethyl sulfoxide (DMSO), was applied to activate the “chemically inert,” but low-cost and abundant CF3-group source, fluoroform (CF3H). Direct trifluoromethylation with CF3H avoided the use of an ozone-depleting reagent, such as bromotrifluoromethane (CF3Br) or iodotrifluoromethane (CF3I). Furthermore, the transformation of a chemical waste like CF3H into valuable fluorochemicals is highly desirable. In addition, a synthetic route to the “super-trifluoromethyl group”-containing building block pentafluorosulfanyl difluoroacetic acid [SF5CF2C(O)OH] was developed. The addition of SF5Br to chlorotrifluoroethylene in the presence of a radical initiator gave 1-pentafluorosulfanyl-1,1-difluoro-2,2,2-fluorochlorobromoethane. Then oxidation of this adduct, followed by hydrolysis gave the desired pentafluorosulfanyldifluoroacetic acid in 82% yield. The pentafluorosulfanylperfluoroalkyl halides SF5CF2I, SF5CF2CF2Br, and SF5CF2CF2I were also prepared for use in the syntheses of other SF5-containing compounds. For example, convenient syntheses were developed for the hydro compound SF5CF2CF2H from either of the latter two reagents. Furthermore, the synthesis of fullerene (C60) derivatives bearing a pentafluorosulfanyl group was investigated by using both of the aforementioned SF5-containing perfluoroalkyl iodides. Bis-1,7-(SF5CF2CF2)2-C60 was selectively synthesized and isolated via collaborative work with the research group of Drs. Strauss and Boltalina at Colorado State University. In addition, the halogen bonding effect was demonstrated from mixtures of pentafluorosulfanylperfluoroalkyl halides and Lewis bases in pentane solution.
Qing, Siyan, "Syntheses and Applications of Trifluoromethyl- and Pentafluorosulfanyl-Containing Organic Molecules" (2017). All Dissertations. 1973.