DD243029B3 - METHOD FOR PRODUCING TRIORGANOSILICIUM COMPOUNDS - Google Patents

Description

Field of application of the invention

The invention relates to the preparation of triorganosilicon compounds, in particular vinyldiorganoalkoxysilanes and 1,3-divinyl-1,1,3,3-tetraorganodisiloxanes. These compounds are intermediates in organosilicon chemistry. They are z. For example, it is used to break down organopolysiloxane chains and is preferably used to prepare addition-crosslinking organopolysiloxanes, e.g. used in potting compounds or in silicone rubber compounds.

Characteristic of the known technical solutions

Both single-stage and two-stage processes are known for the preparation of monosiofunctional triorganosilicon compounds or vinyldiorganosilicon compounds by organylation of higher-functionality silicon compounds with Grignard reagent.

In all the processes described so far, one obtains always a mixture of silicon compounds of different functionality, wherein in addition to monosilicofunktionellem target product always higher functional starting materials and perorganylated compounds in varying, depending on applied stoichiometry and experimental conditions proportions are present. In addition to the reaction-related yield reduction, the unreacted higher-functional starting materials complicate the work-up of the reaction mixture. Since they bind substantial quantities of monosilicofunctional target product in an aqueous workup, the entire monomeric silicon compounds must be separated by dissolution of the magnesium salts in water by filtration or distillation.

So z. B. in the reaction of methylmagnesium chloride in diethyl ether with vinyltrichlorosilane despite 24 hours of extraction of the reaction mixture with ether only yields of not more than 24% of theory and with vinylmethyldichlorosilane of not more than 46% of theory be achieved on vinyldimethylchlorosilane. The vinylation of dimethyldichlorosilane with the difficultly accessible vinylmagnesium bromide in tetrahydrofuran gave 58% of theory. Vinyldimethylchlorosilane. In the methylation of vinyltriethoxysilane with methylmagnesium bromide, only 6% of theory was used. Vinyldimethylethoxysilane and 57% of theory

Vinylmethyldiethoxysilane obtained.

In the previously known one-step Grignard syntheses, the so-called one-pot reactions, for the preparation of vinyldiorganoalkoxysilanes and of 1,3-divinyl-1,1,3,3-tetraorganodisiloxanes, neither the processes described nor the yields achieved can likewise be satisfied.

Thus, vinylmethyldiethoxysilane was methylated with magnesium using the expensive iodomethane without yielding.

In addition, alpha-omega-dichloroorganopolysiloxanes were vinylated with magnesium and chloromethane in tetrahydrofuran. In this reaction, the Grignard compound substitutes in situ the Si-Cl bonds, but at the same time splits the poly siloxane bonds to a considerable extent, so that in the subsequent aqueous workup of the reaction mixture due to unavoidable condensation reactions inevitably always a mixture of homolog divinylpolysiloxanes arises from the the 1,3-divinyl-1,1,3,3-tetramethyldisiloxane by complicated rectifications with yields of only less than or equal to 13.5% of theory could be isolated.

Object of the invention

The aim of the invention is the preparation of triorganosilicon compounds, in particular vinyldiorganoalkoxysilanes and of 1,3-divinyl-1,1,3,3-tetraorganodisiloxanes with the aid of a simple one-step process in high yields.

-2- 243 029 Explanation of the essence of the invention

It has been found that it is possible to use triorganosilicon compounds of the general formula R ¹ R ₂ SiOX in which R = alkyl, aryl and / or alkenyl, R '= alkenyl and X = alkyl or SiR ₂ R', in particular vinyldiorganoalkoxysilane and 1, 3-Divinyltetraorganodisiloxan, very specifically, with Grignard reagent in situ, using technically readily available starting materials in surprisingly high yields. Neither di- or trisilicofunctional starting compounds are obtained, nor are appreciable perorganylations to be expected because of the Grignard excess at the end of the reaction when the following procedure is followed:

Starting compounds of the general formula R _n Si (OR ") _m Cl ₄ _ ( _{n + m) /} in which R" = alkyl, R = alkyl, aryl and / or alkenyl, η = 1 or 2 and m = 0 to 3, or mixtures thereof having a ratio of chlorine to alkoxy substituents equal to or less than 1, are reacted in the form of a one-pot reaction with Grignard reagent generated from magnesium and organohalide to an excess in situ. The reaction, which is initiated by activation, always takes place in the presence of an organic solvent, preferably diethyl ether, methyl tert-butyl ether or tetrahydrofuran, at temperatures less than or equal to 340K. The entire magnesium and the organic solvent is partially or completely presented. The type, sequence and rate of addition of the reactants, or of the activating agent and, if appropriate, of the remaining solvent fraction take place differently depending on the reaction conditions. For example, activated or untreated magnesium may be used and activation may be performed before or after the beginning of the organohalide addition. The metered addition of organohalides can z. B. at different rates, by introducing into or passing over the reaction mixture, and by dropwise addition, if appropriate, in admixture with a solvent content and / or the total amount or a proportion of the starting silicon compound. The starting silicon compound may also be partially or completely charged.

To prepare the Grignard compound z. B. as organohalide methyl, ethyl, vinyl chloride or phenyl bromide can be applied. The solvents used are various ethers, such as diethyl ether, methyl tert-butyl ether or tetrahydrofuran. The activation of the reaction is carried out with commonly used activators, eg. As iodine, alkyl chloride, alkyl halides or Grignard reagent.

The isolation of the organylated products, the triorganosilicon compounds, is greatly simplified due to the high selectivity of the reaction. The aqueous workup can be done immediately without the prior separation of the monomeric compounds, since no appreciable amounts of di- or trisilicofunctional starting compounds in the reaction mixture are more present. After separation of the organic layer, the products according to the invention are purified in a high purity and in high yields up to 85% of theory by a simple rectification. won. The following examples illustrate the process without limiting it.

embodiment

7 grams of magnesium semolina and 1 to 1.5 liters of dry ether are placed in a 6 l sulfonating flask and heated to a maximum of 325 K with stirring. After activating the approach, for. B. with 30 ml of a corresponding Grignard solution, dry organohalide is passed through the stirred mixture at a rate of 0.75 to 1.5 mol / h. After starting the reaction and a short activation phase, 1 to 1.51 dry ether and 5.6 mol disilicofunctional diorganosilicon compound or 2.8 mol trisilicofunktionelle monoorganosilicon compound are added and the reaction for a further 6 to 9 hours at temperatures below 340 K, optionally with cooling or towards the end of the reaction with gentle heating, continued until the occurrence of a Grignard excess. Subsequently, the reaction mixture is decomposed with 21% water, NH ₄ Cl solution or dilute hydrochloric acid with stirring and optionally cooling. The organic layer is separated, washed with water and rectified

 In the following Table 1, some examples summarize the reaction conditions and the results.

Table 1

Reaction conditions and results

Ex. Silicon starting compound in% by mass RR'SiCKOR ") RR'Si (OR ") ₂ cond. organo Cpd. halide RR'SiClz 93 5 1 94 4 1 1 1 - 54 - R'CI 2 1 84 11 2 R'CI 3 46 S3 5 1 R'CI 4 3 R ₂ SiCl (OR ") RSi (OR ") ₃ RO 5 1 95 - 2 R ' "Br RiSiCI ₂ - 99 - 6 2 RCI 7 - R'CI

R = vinyl, R '= methyl, R "= ethyl, R" = phenyl.

Ex. activator Solv. Temp. Yield (% of theory) 1 R'Br / R'MgCI tC ₄ H _e OR ' 307-313 82 (RR ₂ Si) ₂ O 2 R'MgCI R? O 307-310 78 (RR ₂ Si) ₂ O 3 C ₂ H ₄ Br ₂ R ₂ O 307-313 72 (RRJSi) ₂ O 4 R'MgCI (CH ₂ J ₄ O 307-330 75RR ₇ SiOR " 70R ' "R'RSiOR" IX) J ₂ r o 308-311 8515 (R '"R'RSi) ₂ O 6 RMgCI (CH ₂ J ₄ O 313-326 70 RR ₂ SiOR " 7 J ₂ / C ₂ H ₄ Br ₂ R ₂ O 307-310 73 (RRJSi) ₂ O

R = vinyl, R '= methyl, R "= ethyl, R" = phenyl.

Claims (3)

1. A process for the preparation of triorganosilicon compounds of the general formula FTR ₂ SiOX, in which R = alkyl, aryl and / or alkenyl, R '= alkenyl and X = alkyl or SiR ₂ R', in particular of vinyldiorganoalkoxysilanes and 1,3-divinyl Tetraorganodisiloxan, with high selectivity, by reacting Organoalkoxychlorsilanen and / or organoalkoxysilanes or mixtures of organochlorine and organoalkoxysilanes with Grignard reagent in the presence of a solvent and subsequent aqueous work-up, characterized in that starting compounds of the general formula R _n Si (OR ") _m CI ₄ _ _(n + _m) , in which R "= alkyl, R = alkyl, aryl and / or alkenyl, η = 1 or 2 and m = 0 to 3, or mixtures thereof having a ratio of chlorine to alkoxy substituents equal to or less than 1, with Grignard reagent, which is generated from magnesium and organohaiogenid to an excess in situ, are reacted at temperatures less than or equal to 340 K, the Whole magnesium and organic solvents are partially or completely presented and contained in the compounds to be reacted at least one alkenyl group. 2. The method according to claim 1, characterized in that is used as the organic solvent diethyl ether, methyl tert-butyl ether or tetrahydrofuran. 3. The method according to claim 1, characterized in that the Organohaiogenid is methyl, ethyl, vinyl chloride or phenyl bromide.