Process for preparing phenylorganosilicon intermediates

#The present invention relates to a method for preparing phenyl-containing organosilicon intermediates using an aromatic halogenated solvent during the coupling reaction involving a phenyl Grignard reagent and a precursor halosilane. The process comprises contacting a phenyl halide with magnesium in a solvent such as ether, or aromatic halogenated solvent/ether mixtures to form a Grignard reagent, and thereafter contacting the Grignard reagent with a precursor chlorosilane in aromatic halogenated solvent to form the desired organosilicon intermediates, and then filtering and distilling to acquire the organosilicon intermediate reaction product.

#The inventors of the present invention have found that the use of aromatic halogenated solvents in conjunction with ethers, the traditional Grignard reaction solvents, results in lower reaction temperatures, the ability to separate the desired organosilicon intermediate from the by-produced magnesium halides with ease which results in higher yields of purer organosilicon intermediates, and, the created the ability to reduce the amount of waste solvent that normally occurs with the traditional Grignard process.

#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, pp. 76-103, (1967), Methuen and Co. Ltd, London, U.K.; and in Kirk/Othmer, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, Vol. 10, 721-734 (1966), The Interscience Encyclopedia, Inc., NY, 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 Grignard reagents is discussed in the above cited review articles, and the inventors herein believe, but should not be held to such a theory, that the following reaction equations may be the actual mechanisms in the inventive process, wherein by way of example, phenyl chloride is used as the organic halide reactant: 1 Phenyl ⁢ C1 + Mg → { Phenyl ⁢ MgC1 } ⁢ ⟶ aromatic ⁢ ⁢ halogenated solvent MeSiC1 3 ⁢ Phenylmethyldichlorosilane + MgCl 2

#The apparatus for the following examples consisted of a 3-necked, 500 ml, round bottomed glass flask resting on a heating mantle and a supporting jack, the glass flask being adapted with a mechanical stirrer in the central neck, a Claisen adapter with an addition funnel, a rubber septum for sampling, a second Claisen adapter in the third neck of the flask, that holds a thermometer and a ten bulb water condenser, surmounted by a dry ice/isopropanol reflux condenser with a dry ice condenser surmounted on the top of the isopropanol condenser. The apparatus is also equipped with a nitrogen inlet system.

#A Grignard reagent, phenylmagnesiumchloride in diethyl ether was prepared by the reaction of chlorobenzene with magnesium metal at about 170° C. under pressure in a high pressure Grignard reactor.

#In the preparation of the phenyl-containing chlorosilane, methyltrichlorosilane as the precursor organohalosilane (230.3 grams, 1.54 moles) and chlorobenzene (253 grams, 2.24 moles) were loaded into a 1 liter glass flask equipped essentially as the apparatus described above, and heated slowly to 40° C. Liquid Grignard reagent from above, in diethyl ether (250 ml.), was loaded into an addition funnel and slowly added to the silane solution. The reaction exothermed gently to 47° C. The addition was completed in approximately 2.5 hours. A very flowable reaction mixture was obtained. Upon standing at room temperature MgCl2 readily precipitated. No second layer of MgCl2 was observed after several days standing. Gas Chromatography (GC) analysis of the reaction mixture showed that 12 GC area % of PhMeSiCl2, 1 GC area % of Ph2SiMeCl, 43 GC area % of PhCl, 21GC area % of unreacted MeSiCl3, 18 GC area % of diethyl ether, was detected by the analysis. There was no indication of the presence of biphenyl.