The Synthesis and Characterization of Novel Pentafluorosulfanyl-Containing Heterocycles and Pentafluorosulfanyldifluoromethane
Date of Award
Doctor of Philosophy (PhD)
Joseph S. Thrasher
Julia L. Brumaghim
R. K. Dieter
Joseph W. Kolis
Beginning in the early 1960s, scientists began to experiment with the pentafluorosulfanyl moiety. The unique properties of the functional group has attracted interest among fluorine chemists and more recently even organic chemists. These properties include high group electronegativity, high steric bulk, high lipophilicity, a highly electron withdrawing nature, and a square pyramidal geometry. However, the development and deployment of the pentafluorosulfanyl functional group has been significantly slowed. The main cause for the slow development is a lack of easily available reagents to synthesize pentafluorosulfanyl-containing compounds. Historically, the primary reagents used for synthesizing pentafluorosulfanyl-containing compounds were SF5Cl and SF5Br. These two compounds are difficult to synthesize, cost prohibitive, and difficult to utilize without a vacuum line. With the development of a convenient, cost-effective synthesis of phenylsulfur pentafluorides, the presence of pentafluorosulfanyl in synthetic chemistry has been increasing.
Starting from SF5N=CCl2, a number of five-membered heterocycles have been synthesized. Starting from 1,2-substituted binucleophiles, several classes of heterocycles have been formed, including SF5N= substituted carbonates, a pentafluorosulfanylimino-substituted benzothiazolinone, and a pentafluorosulfanylimino-substituted benzoxazolinone.
Another aspect of this work depends on a reagent that has recently been synthesized in a reliable, safe and scalable method, namely pentafluorosulfanyldifluoroacetic acid. Pentafluorosulfanyldifluoroacetic acid can be converted to the corresponding acyl chloride by reaction with PCl5, and subsequently added to the amino group of various 2-amino benzamides. The newly formed 2-pentafluorosulfanyldifluoroacetamido benzamides can then be cyclized to quinazolinones by a dehydration in glacial acetic acid.
From SF5CF2I, pentafluorosulfanyldifluoromethane has been synthesized by two reductive methods. The first method utilized by tri-n-butyl tin hydride to produce SF5CF2H, at 37% yield. The second method utilized a solution of triethylborane in hexanes, with had a yield of 49% of SF5CF2H. Pentafluorosulfanyldifluoromethane was first reported in 1950, though the primary evidence of this discovery was provided in the form of an empirical formula, derived from elemental analysis. Here, a more thorough spectroscopic analysis of the compound is presented, including IR, NMR and Raman spectroscopy.
Belina, Steven Paul, "The Synthesis and Characterization of Novel Pentafluorosulfanyl-Containing Heterocycles and Pentafluorosulfanyldifluoromethane" (2019). All Dissertations. 2373.