Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
  • C07F7/1804—Compounds having Si-O-C linkages
  • C07F7/1872—Preparation; Treatments not provided for in C07F7/20
  • C07F7/1876—Preparation; Treatments not provided for in C07F7/20 by reactions involving the formation of Si-C linkages
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
  • C07F7/1804—Compounds having Si-O-C linkages
  • C07F7/1872—Preparation; Treatments not provided for in C07F7/20
  • C07F7/1888—Preparation; Treatments not provided for in C07F7/20 by reactions involving the formation of other Si-linkages, e.g. Si-N

Definitions

• the present invention relates to a method for preparing di-organo-dialkoxysilanes, in particular di-organo-dialkoxysilanes wherein one or both of the organic substituents are bulky.
• Di-organo-dialkoxysilanes are included, among other things, as stereo modifiers in catalysts for the production of polypropylenes. Particularly advantageous for that use are disubstituted dialkoxysilanes wherein the organic substituents are branched alkyl chains.
• di-organodialkoxysilanes can be produced through alkylation or arylation of tetraalkoxysilanes and only occasionally produced by reaction of mono substituted trialkoxysilanes with Grignard reagents (Houben-Weyl, Methods 25 of Organic Chemistry, XIII/5, 180 p).
• reaction products are produced as mixtures of di-organo- dialkoxysilanes with mono-organo-trialkoxysilanes and/or tri-organo- monoalkoxysilanes, so that the isolation of the desired di-organo-dialkoxysilane requires a separation step.
• An object of the present invention is therefore to provide a method to prepare di- organo-dialkoxysilanes wherein one or preferably both of the organic substituents are bulky, using readily available raw materials, with a relatively simple process, at moderate reaction conditions and resulting in relatively high yields.
• a further object of the present invention present invention is to provide a method to prepare di-organo-dialkoxysilanes wherein the organic substituents may be different.
• Si(-OR 1 ) 2 wherein molar ratio of the second Grignard compound and the chlorinated mono- substituted dialkoxy silane compound is from 1 to 1.5; and wherein R ⁇ R 2 and R 3 are independently selected from the group comprising an alkyl group having 1 to 20 carbon atoms and a cycloalkyl group having 3 to 20 carbon atoms, optionally containing a heteroatom; and X is iodine, bromine or chlorine.
• R 1 and/or R 2 have to be of a certain bulkiness, i.e. they have to bring about a certain steric hindrance effect during the reaction. Without willing to be being bound to it, the present inventors believe that this bulkiness steric hindrance during the reaction of step a) will prevent or at least significantly limit the formation of di-organo-dialkoxysilane compounds.
• the term "predominantly” as used herein is to be understood as meaning that the yield of formation of the mono-organo- trialkoxysilane compound is at least 75% of the theoretical maximum yield based on the amount of tetraalkoxysilane compound.
• step a) Further factors attributing to the formation of predominantly a mono-organo-trialkoxysilane in step a) can be the molar ratio of the first Grignard reagent and the tetraalkoxysilane and/or the reaction conditions, in particular reaction temperature.
• the skilled person will understand that the amount of steric hindrance as a result of the selection of R 1 and R 2 will determine the importance of these further factors. For example, selecting a molar ratio of the first Grignard reagent and the tetraalkoxysilane of below 1.5, preferably below 1.2 will reduce the possibility of formation of di-organo-dialkoxysilane compounds in case the steric hindrance is not strong enough to fully prevent formation of such compounds.
• R 1 and R 2 and/or the reaction conditions are selected such that the yield of the product obtained in step s) is at least 85%.
• step a) is followed by a step b), wherein one alkoxy group is replaced by a chlorine atom, after which in step c) a second Grignard reaction is carried out to replace this chlorine atom with an organic group R 3 .
• This organic group R 3 may be the same or different as R 2 hence allows preparation of a wide variety of bulky substituted dialkoxysilanes, i.e. a wide variety of di-organo-dialkoxysilanes.
• An advantage of the present invention is that it allows the use of readily available and low cost raw materials such as tetramethoxysilane and tetraethoxysilane. Further advantages of the present invention are that the yield of the reaction is relatively high and that the preparation can be carried out at moderate reaction conditions.
• R ⁇ R 2 and R 3 are independently selected from the group comprising an alkyl group having 1 to 20 carbon atoms and a cycloalkyl group having 3 to 20 carbon atoms, optionally containing a heteroatom.
• at least one of R 1 , R 2 and R 3 is a branched alkyl group having 3 to 20 carbon atoms at a secondary or a tertiary carbon situated in a and/or ⁇ position to the silicon atom.
• R 1 , R 2 and R 3 are independently selected from the group consisting of an alkyl group having 1 to 20 carbon atoms and a cycloalkyl group having 3 to 20 carbon atoms, optionally containing a heteroatom and at least one of R 1 , R 2 and R 3 is a branched alkyl group having 3 to 20 carbon atoms at a secondary or a tertiary carbon situated in a and/or ⁇ position to the silicon atom.
• R 1 is a hydrocarbon group having from 1 to 20 carbon atoms, more preferably from 3 to 10 carbon atoms and most preferably from 5 to 10 carbon atoms.
• R 1 can be an alkyl group preferably having from 1 to 10 carbon atoms, and more preferably is selected from a group consisting of methyl, ethyl, n-propyl, iso-propyl, n- butyl, iso-butyl, sec-butyl, n-pentyl, iso-pentyl, n-hexyl,n- heptyl, n-octyl, n-nonyl, n- decyl, preferably ethyl, methyl, n-propyl and iso-propyl. Most preferably, R 1 is methyl or ethyl. R 1 optionally contains a heteroatom.
• R 1 can be also a cyclic hydrocarbon group with 3 to 10 carbon atoms, such as cyclopentyl, cyclohexyl, or a benzyl group.
• R 1 may also be an alkyl or cycloalkyl group containing a hydrocarbon ring having from 5 to 8 carbon atoms.
• Preferably R 1 does not contain a heteroatom.
• R 2 is a tertiary hydrocarbon group, or a cyclic hydrocarbon group preferably having a ring from 5 to 20 carbon atoms or an alkyl group containing a hydrocarbon ring having from 5 to 20 carbon atoms, with the proviso that if R is methyl the cyclic hydrocarbon has a ring from 6 to 20 carbon atoms.
• R 1 is selected to be methyl, the steric hindrance obtained by a cyclic R 2 group having less than 6 carbon atoms possibly results in more formation of reaction products other than the desired a mono-organo-tri-alkoxysilane compound, i.e.
• R 2 is selected from the group consisting of cyclic hydrocarbons having a ring of 5 or 6 carbon atoms and tertiary hydrocarbons having from 3 to 10 carbon atoms.
• R 2 groups include ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, sec-pentyl, tert-pentyl, n-hexyl,n- heptyl, cyclopentyl, cyclohexyl, , cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, benzyl.
• R 2 groups being alkyl groups containing a ring are 1-methyl-cyclohexyl, 1 - ethyl- cyclohexyl and the like. Cyclic hydrocarbons may also contain branches. R 2 optionally contains a heteroatom. Preferably R 2 does not contain a heteroatom.
• R 1 may be the same or different than R 2 .
• R 1 is different than R 2 .
• R 3 may be a hydrocarbon compound having from 3 to 20 carbon atoms optionally containing a hetero atom. Preferably R 3 does not contain a heteroatom.
• R 3 is preferably selected from the group consisting of cyclic hydrocarbons having a ring of from 5 to 10 carbon atoms, secondary hydrocarbon groups having from 3 to 10 carbon atoms and tertiary hydrocarbon groups having from 3 to 0 carbon atoms.
• R 3 may further be an alkyl group containing a ring (cyclic hydrocarbon group), or R 3 may be a cyclic hydrocarbon compound.
• R 3 examples are n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, sec-pentyl, tert-pentyl, n-hexyl,n- heptyl, cyclopentyl, cyclohexyl, , cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, benzyl, 1-methyl-cyclohexyl, 1 -ethyl- cyclohexyl, propyl cyclopentyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, iso-propyl, sec-butyl, tert-butyl, 1
• R 3 may be the same or different than R 2 , preferably R 3 is different than R 2 .
• R 1 is a hydrocarbon group, preferably an alkyl group having from 1 to 10 carbon atoms or a cyclic hydrocarbon group having from 3 to 10 carbon atoms
• R 2 is a secondary or more preferably tertiary hydrocarbon group or a cyclic hydrocarbon group preferably having a ring of from 5 to 20 carbon atoms, with the proviso that if R 1 is methyl the cyclic hydrocarbon has a ring of from 6 to 20 carbon atoms.
• the chlorinating agent used in the method of the present invention may be any compound capable of chlorinating the mono-organo-tri-alkoxysilane compound of step a).
• Particularly suitable for the method of the present invention are inorganic chlorinating agent, such as HCI, AICI 3 , SOCI 2 , PCI 5 and PCI 3 and ZnCI 2) most preferred being HCI and SOCI 2 in view of their availability and reactivity.
• Grignard reagents used in the present invention are typically known in the art and may be made in any manner known to the skilled person, such as for instance as described in Grignard Reagents New developments by H.G. Richey 2000 (ISBN 0471999083).
• the temperature in step a) may be kept between 0° and 25°C, preferably between 5 and 10°C.
• the reaction may be kept in between this range until the reaction of step a) is completed (as monitored by Gas Chromatography), which means until at least 85% or preferably at least 95% of the tetraalkoxysilane compound has reacted.
• the reaction mixture may be kept at the reaction temperature for a certain amount of time, for example between from 1 to 10 hours, preferably between 3 to 8 hours, to further complete the reaction.
• the Grignard reaction of step a) can be carried out in any typically known ether-type solvents, such as for example t-butyl methyl ether and diethyl ether, or in mixed solvent of an ether-type solvent with an aprotic solvent such as hexane, heptane, toluene, and xylene.
• the reaction in step a) is normally carried out under inert atmosphere such as for example under nitrogen or argon, because the presence of oxygen in the reaction system brings about a reaction with the Grignard reagent thus resulting in lowering of the yield.
• an appropriate amount of a saturated aqueous ammonium chloride solution or a dilute sulfuric acid can be added to dissolve magnesium salt.
• the amount of the saturated aqueous ammonium chloride solution or a dilute sulfuric acid depends on the amount of the tetraalkoxysilane. For instance, about 10 to 15 ml saturated solution of ammonium chloride may be added for 10 g of tetraalkoxysilane.
• the organic layer is then typically separated from the aqueous layer.
• the organic layer so separated may be purified by any method known in the art, for instance by fractional distillation under atmospheric or reduced pressure, whereby there can be recovered a fraction consisting of the desired reaction product, which is the monoalkoxysilane.
• the molar ratio of the first Grignard compound and the tetraalkoxysilane compound may have to be from 1 to 1.5, preferably from 1 to 1.2 and more preferably between 1 to 1.1 , so as to prevent undesirable formation of di-organo-dialkoxysilane compound.
• the ratio is below 1 , the tetraalkoxysilane remains unreacted; whereas higher ratios yield more by-products i.e. and decrease the yield of the reaction.
• the materials used in step a) may be added in any order and mixed in any manner known in the art.
• the tetraalkoxysilane in step a) may be a single tetraalkoxysilane compound or a mixture of different tetraalkoxysilane compounds, preferably a single tetraalkoxysilane compound.
• the first Grignard reagent in step a) may be a single first Grignard reagent or a mixture of different first Grignard reagents, preferably a single first Grignard reagent.
• Step b) During step b), the reaction temperature may be kept at moderate temperatures, for example a temperature in the range from 10°C to 50°C, preferably at room
• the chlorinated mono-organo-di-alkoxysilane compound can be obtained.
• step b) may be added in any order and mixed in any manner known in the art.
• the chlorinated agent may be added gradually to the mono-organo-tri-alkoxysilane, in a certain period of time, such as within maximum 1 hour.
• the amount of the chlorinating agent is preferably equivalent to the amount of mono- organo-trialkoxysilane compound, yet the molar ratio between the mono-organo-tri- alkoxysilane compound to the chlorinating agent may range from 1 to 1.5, preferably from 1 to 1.2, more preferably from 1 to 1.1. In case the ratio is below 1 , the mono- organo-tri-alkoxysilane remains unreacted; whereas higher ratios yield more byproducts i.e. and decrease the yield of the reaction.
• the obtained reaction product in step b) may be then purified by any means known in the art, preferably by means of distillation.
• the chlorinating agent may be a single chlorinating agent or a mixture of different chlorinating agents. Preferred it is a single chlorinating agent.
• the temperature in step c) may be kept between 0° and 25°C, preferably between 5 and 10°C.
• the reaction may be kept in between this range until the reaction of step c) is completed (as monitored by Gas Chromatography), which means until at least 95% of mono-organo-di-alkoxysilane compound has reacted.
• the reaction mixture may be kept at the reaction temperature for a certain amount of time, for example between from 1 to 10 hours, preferably between 3 to 8 hours, to complete the reaction.
• the Grignard reaction of step c) can be carried out in any typically known ether-type solvents, such as for example t-butyl methyl ether and diethyl ether, or in mixed solvent of an ether-type solvent with an aprotic solvent such as hexane, heptane, toluene, and xylene.
• ether-type solvents such as for example t-butyl methyl ether and diethyl ether
• an aprotic solvent such as hexane, heptane, toluene, and xylene.
• step c) is normally carried out under inert atmosphere such as for example under nitrogen or argon, because the presence of oxygen in the reaction system brings about a reaction with the Grignard reagent thus resulting in lowering of the yield.
• an appropriate amount of a saturated aqueous ammonium chloride solution or a dilute sulfuric acid can be added to dissolve magnesium salt.
• the amount of the saturated aqueous ammonium chloride solution or a dilute sulfuric acid typically depends on the amount of the mono-organo-di- alkoxysilane. For instance, about 10 to 15 ml saturated solution of ammonium chloride may be added for 14 g of mono-organo-di-alkoxysilane. The organic layer is then typically separated from the aqueous layer.
• the organic layer so separated may be purified by any method known in the art, for instance by fractional distillation under atmospheric or reduced pressure, whereby there can be recovered a fraction consisting of the desired reaction product, which is the di-organo-di-alkoxysilane compound.
• the molar ratio of the second Grignard compound and the chlorinated mono- substituted dialkoxy silane compound is from 1 to 1.5 preferably from 1 to 1.2, most preferably from 1 to 1.1. In case the ratio is below 1 , the chlorinated mono-substituted dialkoxy silane remains unreacted; whereas higher ratios yield more by-products i.e. and decrease the yield of the reaction.
• the second Grignard reagent in step c) may be a single second Grignard reagent or a mixture of different second Grignard reagents; preferably a single second Grignard reagent.
• step c) may be added in any order and mixed in any manner known in the art.
• the second Grignard reagent is prepared separately and afterwards added to the chlorinated mono-substituted dialkoxy silane. After this, the mixture may be kept at reflux temperature (typically determined by the boiling point of the solvent) until reaction is completed, generally between 1 and 6 hours, preferably between 3-6 hours.
• chlorocyclopentyldiethoxysilane (d) were charged in a 250 ml flask equipped with a reflux condenser and a stirring apparatus in an atmosphere of nitrogen and above prepared solution of isobutyl magnesium bromide was slowly added while keeping the internal temperature below 10 °C. After completion of addition stirring was carried out at room temperature for 6 hours and at reflux temperature for 2 hours. To the resulting reaction mass 10-20 ml of saturated aqueous ammonium chloride solution was added drop wise to dissolve magnesium salt. The organic layer was separated from the aqueous phase, dried and evaporated to give crude cyclopentylisobutyldiethoxysilane.

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