Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2002-06-13
2004-02-03
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
Reexamination Certificate
active
06686492
ABSTRACT:
BACKGROUND OF INVENTION
The present invention is directed to a one step Grignard-type process for preparation of an organosilane. The process comprises contacting a mixture of an organic halide in a co-solvent mixture of an ether and an organic solvent with magnesium metal in an ether and an organic solvent, and reacting this mixture with an organohalosilane. The present inventors have found that the presence of the co-solvent mixture of an ether and an organic solvent provides for a product slurry that stirs and flows easily. These characteristics of the product slurry improve mass transfer and heat transfer during the process and allows for easier separation of the organosilane from the product slurry. Conduct of the present process in the co-solvent provides for improved ratios of the desired organosilane to byproducts and improved recovery of the product from the resultant slurry. Furthermore, the use of the co-solvent allows the process to be run as a continuous process. The process can be self-initiating when it is run with the co-solvent. The process is particularly useful for making bisorganosilylbenzene intermediates.
The reaction of organic halides with magnesium metal in the presence of oxygenated solvents such as dialkyl ethers to form reactive complexes, typically referred to as Grignard reagents, is well known. The production and reactions of Grignard reagents has been the subject of books and numerous review articles. Such reviews are provided, for example, in Coates, et al.,
ORGANOMETALLIC COMPOUNDS
, vol. 1, p. 76-103, (1967), Methuen and Co., LTD, London, U.K., and Kirk and Othmer,
ENCYCLOPEDIA CHEMICAL
, vol. 10, p. 721-734 (1966), The Interscience Encyclopedia, Inc., New York, N.Y. The structure of the Grignard reagent has not been determined with certainty, however, it is generally believed that the Grignard reagent exists as a complex in solution and that solvent can play a critical role in such complex formation. The unpredictable effect of solvent on the formation and reactivity of the Grignard reagents is discussed in the above cited review articles.
The preparations of organosilicon compounds using a Grignard reagent as an intermediate are known. However, nowhere in the art is there shown the preparation of organosilicon intermediates from a group which includes such intermediates as 1,4-bis(dimethylsilyl)benzene, 1,4-bis(dimethylchlorosilyl)benzene, and their derivatives. Turk et al.,
Organic Synthesis
, vol. 27, 7-8, 1947, teach a process for preparing organic intermediates in anhydrous ether with magnesium turnings. Turk et al. teach that this reaction results in the formation of a thick slurry that becomes unstirrable. This unstirrable slurry is then treated with a hydrochloric acid solution until the magnesium chloride byproduct is in solution and the slurry becomes sufficiently fluid to be stirred.
Such processes as taught by Turk et al. are not generally acceptable as commercial processes. The formation of the unstirrable slurry during the reaction can cause reduced mass transfer and heat transfer, and therefore, reduced yield. Furthermore, the nature of the slurry makes it necessary to treat the slurry in an additional step with a reagent to solubilize the slurry to allow isolation of the product. Typically, a major portion of the product is trapped with the unstirrable slurry. In addition, the nature of the slurry does not allow for the reaction to be run as a continuous process.
It is an objective of the present invention to provide a one step process for preparing organosilanes using a Grignard type reagent as an intermediate, where the process avoids many of the above discussed problems with Grignard type processes by creating a reaction mixture slurry that is flowable and easily stirred. Thus, mass transfer and heat transfer can be improved in the reaction mixture providing for improved yield of organosilane. In addition, the formation of a slurry that is flowable allows for the conduct of the process as a continuous process. No additional steps are necessary to solubilize the slurry to make it flowable and allow for recovery of the organosilane.
The present inventor has found that when an organic halide is contacted with magnesium metal in the presence of a organohalosilane and a co-solvent mixture comprising an ether and a liquid hydrocarbon, the resultant slurry is flowable and easily stirred. Furthermore, yields of the desired organohalosilane are improved due to, for example, improved ratios of the organohalosilane to byproducts and the ability to recover the product from the slurry. The flowable nature of the resulting slurry allows the process to be run as a continuous process.
Richards, et al., U.S. Pat. No. 3,080,324 teach that an oxygenated solvent and a liquid hydrocarbon can be used as a reaction medium in the preparation of a Grignard reagent. Richards, et al., do not teach that their co-solvent system is useful in subsequent reactions of the Grignard reagent with organohalosilanes.
Fletcher, et al., U.S. Pat. No. 3,801,558, teach that advantages can be realized when the reducing agent used in preparing the magnesium-reduced catalyst is an organomagnesium Grignard reagent prepared in a hydrocarbon solvent containing a controlled amount of a complexing agent for the Grignard reagent, such as a dialkyl ether. The reported advantage is that the Grignard reagent may be more soluble in hydrocarbon solvents at ambient temperature. Fletcher, et al., report the use of the Grignard as a reducing agent for titanium trichloride in a process for making a catalyst useful in polymerizing alpha-olefins.
The reaction of Grignard reagents with organohalosilanes is well known and many such reactions are described in Kharash, et al.,
Grignard Reactions of Nonmetallic Substances
, Prentice-Hall, Inc., New York, 1954, p.1306-1331.
Takamizawa, et al., U.S. Pat No. 4,593,112, teach that tert-hydrocarbyl silyl compounds can be synthesized by reacting a tert-hydrocarbylmagnesium halide with a silane compound having at least one silicon-bonded hydrogen atom and at least one silicon-bonded halogen simultaneously in a molecule in a suitable organic solvent. Takamizawa, et al., suggest that the solvent may be a mixture of an ether and an aromatic hydrocarbon solvent.
SUMMARY OF INVENTION
The present invention is a one step Grignard-type process for preparation of organosilanes. The process comprises contacting a mixture of an organic halide in a co-solvent mixture of an ether and an organic solvent with magnesium metal, and reacting this mixture with an organohalosilane. These characteristics of the product slurry improve mass transfer and heat transfer during conduct of the process and allows for easier separation of the organosilane from the product slurry. Conduct of the present process in the co-solvent provides for improvement ratios of the desired organosilane to byproducts and improved recovery of the product from the resultant slurry. Furthermore, the use of the co-solvent allows a process to be run as a continuous process. The process can be self-initiating when run with the co-solvent. The process is particularly useful for making bisorganosilylbenzene intermediates.
DESCRIPTION
The present invention is a one step Grignard-type process for preparation of organosilanes. The process comprises contacting a mixture of an organic halide, described by the formula, R
1
X
a
, in a co-solvent mixture of an ether and an organic solvent with magnesium metal in an ether and an organic solvent, and reacting this mixture with an organohalosilane, described by the formula, R2bHcSiX
d
, where each R
2
and R
1
is independently selected from a hydrocarbon group comprising one to about 6 carbon atoms, a=1, 2, or 3, b=0 to 3, c=0 to 3, d=0 to 3, and X is selected group consisting of chlorine and bromine atoms.
By “one step” it is meant that is not necessary to isolate an intermediate Grignard type reagent in the process and further react this Grignard type reagent with organohalosilanes to form the desired organohalosilane interm
Barts Samuel
Dow Corning Corporation
McKellar Robert L.
LandOfFree
Preparation of organosilicon intermediate and their... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Preparation of organosilicon intermediate and their..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Preparation of organosilicon intermediate and their... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3321552