RU2565675C1 - Method of producing methylbenzyl alkoxysilanes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: disclosed is a method of producing methylbenzyl alkoxysilanes by reacting methyl alkoxysilane, benzyl chloride and magnesium metal in the absence of organic solvents.

EFFECT: method is technologically effective and provides high output of methylbenzyl alkoxysilanes, which are suitable for synthesis of novel methylbenzyl siloxane polymers.

7 cl, 2 dwg, 3 ex

Description

The invention relates to the field of chemical technology for the preparation of monomeric organosilicon compounds, which may find application as starting materials for the preparation of organosilicon polymers. Organosilicon polymers have a unique set of valuable properties and, accordingly, a wide range of practical applications. Their widespread use and, accordingly, production is constantly growing, and the search for new compounds that expand the range of useful properties and environmentally friendly methods for their preparation remains an urgent task. The development of technologically advanced methods for producing new monomeric functional organosilanes is a necessary condition for creating new organosiloxane polymers based on them.

More specifically, the invention relates to a method for producing new functional organosilanes - methylbenzylalkoxysilanes, aryl-containing analogues of known methylphenylalkoxysilanes.

The introduction of organic substituents containing an aromatic group is known to provide a number of serious advantages. By the example of compounds containing a phenyl group at the silicon atom, it is known that such compounds are more heat-resistant, more resistant to heat and oxidation than methylsiloxanes, and phenyl groups introduced into the polysiloxane molecule also stabilize methyl substituents in a certain way. The introduction of phenyl substituents also leads to the achievement of more satisfactory mechanical properties of siloxane polymers. Their analogue, benzyl-containing organosilicon polymers, was not obtained due to the lack of technological processes for the preparation of functional benzylsilanes. Alkyl-functional silanes are preferable, as they are more environmentally friendly both in the method of preparation and in the processing conditions, in comparison with the more studied chlorofunctional organosilanes.

It is known that benzylchlorosilanes were synthesized by organomagnesium synthesis [Journal of Organometallic Chemistry 1981, V. 218, No. 2, P. 147]. The yield of benzyldimethylchlorosilane can reach 70% when carrying out the reaction using diethyl ether.

Known reaction of the interaction of benzyl chloride with hydridchlorosilanes using various kinds of catalysts, leading to the production of benzylchlorosilanes [J. Am. Chem. Soc. - 1969, V. 91 No. 13, P. 3666; Organometallics - 2003, V. 22, P. 529].

Benzylsilanols are known from the corresponding benzylchlorosilanes synthesized in turn by the Grignard reaction using benzyl magnesium chloride [Nippon Kagaku Zassi 1960, Vol. 81 P. 11].

The listed processes use aggressive chlorosilanes as starting compounds, which makes them non-technological and environmentally unsafe.

A known method of producing methylphenyl dialkoxysilanes based on methyltrialkoxysilane by the Grignard reaction in an environment of ethereal solvents (CN103113400), as a result of which the process is quite dangerous and, accordingly, low-tech.

Known synthesis of methylphenyl diethoxysilane by organomagnesium synthesis in the absence of organic solvents by the interaction of methyltriethoxysilane, phenyl chloride and magnesium metal (Patent No. 470505 Italy, 1952). The process conditions are stringent, the reaction was carried out in an autoclave at a pressure and a high temperature of 150-160 ° C for 10 hours, while the yield of products was 70%.

A known method of producing benzylalkoxysilanes by organomagnesium synthesis based on tetramethoxysilane and triethoxysilane [MLC 1955, No. 25, S. 1124]. The yield of target compounds is very low, not exceeding 10%.

Closest to the claimed method is a method for producing a mixture of benzyl ethoxysilanes by the interaction of benzyl magnesium chloride and triethoxysilane while boiling in anhydrous ether medium [JACS 1951, V. 73 No. 2, P. 865-865]. The disadvantages of the process are dangerous and accordingly non-technological boiling of the ether reaction solution and the low yield of the target benzyldiethoxysilane, which did not exceed 12%.

The objective of the invention is to obtain a new technical result, which consists in creating a new safe and technologically advanced way to obtain functional organosilicon monomer compounds - methylbenzylalkoxysilanes suitable for the synthesis of new methylbenzylsiloxane polymers.

The problem is solved in that a method for producing methylbenzylalkoxysilanes has been developed, which consists in the reaction of methylalkoxysilane, benzyl chloride and magnesium metal in the absence of organic solvents. Methyl alkoxysilane is selected from the range: methyltrialkoxysilane and dimethyldialcoxysilane, where the alkoxy group is a methoxy or ethoxy group.

In particular, a reaction is carried out using methyltrialkoxysilane. The general reaction scheme is as follows:

In particular, a reaction is carried out using dimethyldialcoxysilane. The general reaction scheme is as follows:

In particular, methyl alkoxysilanes in which the alkoxyl group is ethoxyl are used as starting compounds.

In particular, methyl alkoxysilanes in which the alkyl group is methoxyl are used as starting compounds.

In particular, the ratio of reagents methylalkoxysilane, benzyl chloride and magnesium metal is 2.5: 1: 1.5.

The synthesized compounds were analyzed using GLC and ¹ H NMR spectroscopy. The analysis results fully confirmed the structure of the compounds.

In contrast to the known method, the disadvantages of which are the low yield of the target benzyldiethoxysilane, which did not exceed 12%, and the presence of an organic solvent - ether, the advantage of this method is the high yield of the target product, ~ 70%, significantly exceeding the previously achieved, as well as the absence of organic ethereal solvents that make the process dangerous and, accordingly, low-tech. This allowed us to obtain a new technical result, which consists in creating an effective and technologically advanced method for producing benzylmethylalkoxysilanes, due to the fact that the reaction of methylalkoxysilane, benzyl chloride and magnesium metal in the absence of organic solvents is carried out.

The role of the solvent is played by an excess of methyl alkoxysilane reagent. The optimal ratio is the 2.5th excess of triethoxysilane and the 1.5th excess of magnesium relative to the amount of benzyl chloride added. With a further increase in the content of these reagents, the yield of the target product does not increase.

An important feature of the organomagnesium process involving benzyl chloride is the absence of the need to activate the reaction with standard activators - dibromoethane, iodine, phenyl bromide, used in the reaction of phenyl chloride with ethoxysilanes. This is explained by the rather high activity of benzyl chloride in comparison with phenyl chloride in the Grignard reaction.

The effect of the type of organic radical of the alkoxyl group at the silicon atom was insignificant; the yield of the target product in the case of the starting methyltrimethoxysilane was 67%. It should be noted that this is an important advantage of benzyl-containing compounds in comparison with phenyl-containing compounds, for which synthesis using methoxysilanes is impossible.

In FIG. 1 shows the GLC curve of methylbenzyldiethoxysilane obtained in example 1.

In FIG. 2 shows ¹ H NMR (CDCl ₃ ) spectrum of methylbenzyldiethoxysilane obtained in example 1.

The invention can be illustrated by the following examples.

Example 1. Synthesis of methylbenzyldiethoxysilane.

A mixture of 445 g (2.5 mol) of methyltriethoxysilane and 126.5 g (1 mol) of benzyl chloride is added to 36 g (1.5 mol) of magnesium, while boiling. The reaction mixture is stirred for 6 hours at a temperature of 150 ° C. Next, the reaction mass is filtered, an excess of methyltriethoxysilane is distilled off. The product was isolated by fractionation in vacuo. T _bale. = 120-122 ° C (14 mbar). Colorless liquid. Yield 70%. Spectrum ¹ H NMR (CDCl ₃ ), δ (ppm): 0.05 (s, 3H, SiCH ₃ ) 2.19 (s, 2H, Si CH ₂ C ₆ H ₅ ), 7.21-7.09 (m, 5H, SiCH ₂ C ₆ H ₅ ), 3.78-3.70 (m, 4H, Si (OC H ₂ CH ₃ )), 1.19 (t, 6H, Si (OCH ₂ C H ₃ )).

Example 2. Synthesis of methylbenzyldimethoxysilane

A mixture of 340 g (2.5 mol) of methyltrimethoxysilane and 126.5 g (1 mol) of benzyl chloride is added to 36 g (1.5 mol) of magnesium, while boiling. Then the reaction mixture is boiled for 6 hours at a temperature of 112 ° C. Next, the reaction mass is filtered, methyltrimethoxysilane is distilled off. The product was isolated by fractionation in vacuo. T _bale. = 95-96 ° C (14 mbar). Colorless liquid. Yield 67%. Spectrum ¹ H NMR (CDCl ₃ ), δ (ppm): 0.08 (s, 3H, SiCH ₃ ) 2.22 (s, 2H, Si CH ₂ C ₆ H ₅ ), 7.27-7.08 (m, 5H, SiCH ₂ C ₆ H ₅ , 3.51 (s, 9H, Si (OCH ₃ ) ₃ ).

Example 3. Synthesis of dimethylbenzylethoxysilane

A mixture of dimethyldiethoxysilane 370 g (2.5 mol) and benzyl chloride 126.5 g (1 mol) are added to 36 g (2 mol) of magnesium. Then the reaction mixture is boiled for 6 hours at a temperature of 130 ° C. Next, the reaction mass is filtered, methyltrimethoxysilane is distilled off. The product is isolated by fractionation at atmospheric pressure. T _bale = 199 ° C. Colorless liquid. Yield 65%. Spectrum ¹ H NMR (CDCl ₃ ), δ (ppm): 0.08 (s, 6H, SiCH ₃ ) 2.18 (s, 2H, Si CH ₂ C ₆ H ₅ ), 7.21-7.04 (m, 5H, SiCH ₂ C ₆ H ₅ ), 3.69-3.60 (m, 2H, Si (OC H ₂ CH ₃ )), 1.17 (t, 3H, Si (OCH ₂ C H ₃ )).

Claims (7)

1. The method of producing methylbenzylalkoxysilanes, which consists in the fact that they carry out the reaction of methylalkoxysilane, benzyl chloride and magnesium metal in the absence of organic solvents. 2. The method according to p. 1, characterized in that the methyl alkoxysilane is selected from the series: methyltrialkoxysilane and dimethyldialcoxysilane, where the alkoxy group is a methoxy or ethoxy group. 3. The method according to p. 1, characterized in that the reaction is carried out using methyltrialkoxysilane. 4. The method according to p. 1, characterized in that the reaction is carried out using dimethyldialcoxysilane. 5. A method according to claim 1, characterized in that methyl alkoxysilanes in which the alkoxyl group is ethoxyl are used as starting compounds. 6. The method according to p. 1, characterized in that as the starting compounds use methylalkoxysilanes in which the alkyl group is methoxy. 7. The method according to p. 1, characterized in that the ratio of reagents methylalkoxysilane, benzyl chloride and magnesium metal is 2.5: 1: 1.5.

Images