Organic compounds -- part of the class 532-570 series – Organic compounds
Reexamination Certificate
2002-03-22
2002-11-12
Shaver, Paul F. (Department: 1627)
Organic compounds -- part of the class 532-570 series
Organic compounds
C252S299010
Reexamination Certificate
active
06479645
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to sulfurpentafluoride compounds having a substituted silyl group wherein at least one of the substituents is hindered and methods for making and using same. This invention also relates to the use of these compounds, for example, as precursors to liquid crystal components, surfactants, bioactive compounds in agrochemical and pharmaceutical compositions, or in polymers.
The development of synthetic methodologies for the introduction of sulfurpentafluoride or pentafluorosulfuranyl groups (“SF
5
”) into organic compounds has been pursued with a considerable degree of interest by several research groups. It is believed that the SF
5
group may impart unique properties to these organic compounds that include, inter alia, low surface energy, high chemical resistance, high thermal stability, high electronegativity, hydrophobicity, and high dielectric constant. For instance, the high electronegativity value of the SF
5
group, 3.62 on the Pauling scale, and greater electron withdrawing ability may make it an attractive alternative for the trifluoromethyl group (“CF
3
”) found in many commercial products.
Organic compositions containing SF
5
have been used in a variety of applications. For example, EP 444822, issued to Hansen and Savu describes pentafluorosulfuranyl fluoroaliphatic compositions that are used as surfactants. The reference, Kovacina et. al., Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 2, 170, describes SF
5
-containing polymers that are prepared from mono and bis (pentafluorosulfur)-substituted diacetylenes. These polymers are soluble in fluorinated solvents and are not shock sensitive in comparison to the hydrocarbon analog. U.S. Pat. No. 6,136,838 describes sulfur pentafluorophenyl pyrazoles that are used for the control of ecoparasitic infections. Lastly, DE 19748109 issued to Kirsch et. al (“Kirsch”) describes the preparation of several sulfurpentafluoride derivatives which are used to prepare liquid-crystal media.
Ethynylsulfur pentafluoride (SF
5
CCH) has been oftentimes used as a synthetic intermediate or delivery vehicle for the introduction of the SF
5
-moiety into complex organic compounds. Current methods to isolate SF
5
CCH have only been achieved in small scale, multi-step reactions. See, e.g., Hoover and Coffman, J. Am. Chem. Soc. 1964, 29, 3567(“Hoover”); Canich et. al. Inorg. Chem. 1985, 24, 3668 (“Canich”). Both Hoover and Canich describe four-step reactions to prepare SF
5
CCH from acetylene and either sulfur chloride or sulfur bromide pentafluoride. The yields from these reactions ranged from 9 to 19%. Canich also describes a method of isolating ethynylsulfur pentafluoride via dehydrobromination of SF
5
CH═CHBr with a 49% yield. In the first step, SF
5
CH═CHBr was prepared in 80% yield from the reaction of acetylene and SF
5
Br which took approximately 4 days and was conducted at 57° C. Based upon this, the expected yield of ethynylsulfur pentafluoride after completion of the second step would be approximately 39%. Dehydrohalogenation of the acetylene SF
5
CH═CHCl resulted in product yields of only 1-2% of the desired alkyne. The relatively low yields, inefficiency, and long cycle times may make these processes impractical for large-scale industrial applications. Moreover, the reaction of acetylene with SF
5
Br or SF
5
Cl at high temperatures may be explosive.
Ethynylsulfur pentafluoride may also be obtained by the desilylation of its trialkylsilyl derivative. See Wessel et. al. Chem. Ber. 1986, 119, 45 (“Wessel”). Like the aforementioned methods to isolate SF
5
CCH, the trimethylsilyl derivative of ethynylsulfur pentafluoride is impractical to produce on an industrial scale. The trimethylsilyl derivative of ethynylsulfur pentafluoride prepared as described in Wessel was obtained with only a 12% isolated yield.
Accordingly, there is a need in the art to provide novel compounds that deliver the SF
5
group into an organic compound. Depending upon the application, there may be a further need to provide novel compounds that deliver a substituted silyl group to an organic compound. There is also a need in the art for safe industrial processes to make SF
5
synthetic intermediates at greater yields, less cycle time, lower process temperatures, less volatility, and in a single reaction vessel. Due to the difficulties in the art in isolating the trimethylsilyl derivative of ethynlsulfur pentafluoride, it is thus surprising and unexpected to produce novel substituted-silyl sulfurpentafluoride compounds at relatively high yields when at least one of the substituents of the silyl group is hindered.
All references cited herein are incorporated herein by reference in their entirety.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed, in part, to sulfurpentafluoride-containing compounds having a substituted silyl group. Specifically, in one embodiment of the present invention, there is provided a compound of the formula:
wherein the substitutents R, R′, and R″ may be an alkyl, a substituted alkyl, an aryl, a substituted aryl, or combinations thereof and at least one of the substitutents is hindered. In a preferred embodiment, R, R′, and R″ comprise isopropyl. In another preferred embodiment, R and ′ comprise methyl and R″ comprises t-butyl.
In a further embodiment of the present invention, there is provided a compound comprising a sulfurpentafluoride group and a substituted silyl group that is bonded to the sulfurpentafluoride group by a C—C triple bond. The substituted silyl group has substituents selected from the group consisting of an alkyl, a substituted alkyl, an aryl, a substituted aryl, or combinations thereof and at least one of the substituents is hindered. In another embodiment of the present invention, there are provided liquid crystal precursors that comprise the compounds of the present invention.
In yet a further embodiment of the present invention, there is disclosed a method for making a substituted silyl sulfurpentafluoride ethyne compound wherein the substituents on the silyl group are selected from the group consisting of an alkyl, a substituted alkyl, an aryl, a substituted aryl, or combinations thereof and at least one of the substituents is hindered. The method comprises the steps of: combining a substituted silyl acetylenic compound with a SF
5
-containing halide under conditions sufficient to provide an intermediate product and exposing the intermediate product to a base under conditions sufficient to provide the ethyne compound. In certain preferred embodiments, the combining step is conducted in the presence of a solvent.
These and other aspects of the invention will become apparent from the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to sulfurpentafluoride-containing compounds having a substituted silyl group and methods for making and using same. The compounds of the present invention are suitable for use by themselves or in delivering sulfurpentafluoride groups and/or silyl groups to a variety of organic compositions. In addition, the methods of the present invention produce sulfurpentafluoride-containing compounds at production yields unattainable heretofore.
The compounds of the present invention comprise at least one sulfurpentafluoride grouping that is joined to a substituted silyl group via an unsaturated carbon bond. Preferably, the compound is an ethyne compound wherein the sulfurpentafluoride group is joined to the substituted silyl group via a C—C triple bond. At least one of the substituents on the silicon atom is hindered. The term “hindered” or “sterically hindered” as used herein relates to radical groups that impede or retard a given reaction with another molecule by virtue of its size. Some non-limiting examples of hindered alkyl groups include large primary (1
o
) alkyl groups such as octadecyl or nonadecyl; secondary (2
o
) alkyl groups such as isopropyl, isobutyl, or isopentyl; or tertiary (3
o
) alkyl groups such as tert-butyl
Lal Gauri Sankar
Minnich Kristen Elaine
Air Products and Chemicals Inc.
Chase Geoffrey L.
Shaver Paul F.
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