Silacyclobutanes and process for preparation

Abstract: Novel silacyclobutanes useful as silylating agents and a process for their preparation are provided. The process comprises reacting a halogen substituted silacyclo­ butane with a silylating reagent to exchange the halogen substituents with groups on the silylating reagent. The novel compounds are of the formula wherein R′ is a monovalent substituted or unsubstituted hydrocarbon radical or Y group; R″ and R‴ are independently hydrogen, monovalent substituted or unsubstituted hydrocarbon radical; and Y is selected from: and the disubstituted silacyclobutane wherein both Y and R′ are CH₃O-.

Description: Novel silacyclobutanes, useful as silylating agents, and a process for their preparation, as well as for the preparation of many prior art compounds, are provided. The process comprises reacting a halogen substituted silacyclobutane with a silylating reagent to exchange the halogen substituents with groups on the silylating reagent. This invention comprises a process for preparing a silacyclobutane of the formula in accordance with the reaction wherein A is a monovalent substituted or unsubstituted hydrocarbon radical or halogen; Hal is a halogen; R is a monovalent substituted or unsubstituted hydrocarbon radical; R' is a monovalent substituted or unsubstituted hydrocarbon radical if A is a monovalent substituted or unsubstituted hydrocarbon radical; R' is a Y group if A is halogen; R'' and R''' are independently hydrogen, monovalent substituted or unsubstituted hydrocarbon radical; Y is a monovalent group having an oxygen atom which bonds to the silicon atom of the silacyclobutane; and x is an integer of from 0 through 3. Exemplary of suitable monovalent radicals for R, R', R'' and R''' are hydrogen, hydrocarbons and substituted hydrocarbons. Thus, for example, R, R', R'' and R''' can be alkyl such as methyl, ethyl, propyl or octadecyl; substituted alkyl such as aminopropyl or thiopropyl; haloalkyl such as chloropropyl; aryl such as phenyl, xenyl or naphthyl; alkaryl such as tolyl or xylyl; aralkyl such as benzyl; unsaturated alkenyl such as vinyl, propenyl or hexenyl; or unsaturated alkynyl such as acetylenyl or propynyl. R is preferably methyl, ethyl, vinyl or hydrogen and most preferably methyl. R' can be Y, which is selected from Additionally both Y and R' may be Alkyl groups shown as CH₃ in these formulations for Y may be replaced by other monovalent hydrocarbon radicals. R'' and R''' are preferably hydrogen or methyl. The cyclobutane ring may be substituted or unsubstituted. In either case, the nomenclature used in this application will be "silacyclobutane". The following halogenated silacyclobutanes are prepared using conventional Grignard reaction conditions. The 1,1-dichlorosilacyclobutane is prepared from 3-chloropropyltrichlorosilane and magnesium. The 1-chloro-1-methyl-silacyclobutane is prepared from 3-chloropropylmethyldichlorosilane and magnesium. The 1,2-dimethyl-1-chlorosilacyclobutane is prepared from Methyl(3-chloro-3-methylpropyl)dichlorosilane and magnesium. The 1,1-dichloro-3-methylsilacyclobutane is prepared from (3-chloro-2-methylpropyl)trichlorosilane and magnesium. The desired product is obtained to some degree regardless of the ratio of silane to magnesium employed. For efficiency of operation and best yields, however, it is preferred to use about an equimolar ratio. It is also best to conduct the reaction in the presence of an inert solvent to aid in establishing contact between the reactants and as a suspension medium for the by-product MgCl₂. Conventional anhydrous solvents such as the hydrocarbon ethers, including cyclic ethers such as tetrahydrofuran, can all be used. The starting organofunctional silane, R x SiY 4-x , can be prepared by conventional routes. For example, trimethylsilylacetate is prepared by reaction of trimethylchlorosilane with acetic acid, acetic anhydride or sodium acetate. Dimethylvinylsilylformate is prepared by reaction of dimethylvinylchlorosilane with sodium formate. Methylvinylbis(methylethylketoximo)silane is prepared from the reaction of methylvinyldichlorosilane and methylethylketoxime. Methylvinylbis-(diethylaminoxy)silane is prepared from methylvinyldichlorosilane and diethylhydroxylamine. The novel reaction described above for preparing the organofunctional silacyclobutane is efficient and quantitative and can be conducted at a mild temperature between about -50°C. and about 100°C., generally without a solvent. Typical solvents can be employed, however, such as toluene, tetrahydrofuran, benzene, chloroform or methylene chloride. The preferred ratio of silacyclobutane to silylating agent is such that the ratio of halogen to Y group is 1 to 1, but other ratios could be used if desired. When R is a low molecular weight group such as methyl or vinyl, R x Si(Hal) 4-x is the most volatile species of the reaction, allowing it to be removed by vacuum to drive the reaction to the desired product. No heating, catalyst or purification steps are necessary. The organofunctional silacyclobutane product may be isolated without distillation by removal of the chlorosilane by-product using reduced pressure, heat or both. Alternatively, the organofunctional silacyclobutane product can be recovered by distillation. Novel compounds that can be prepared by the process of the invention are represented by the formula wherein R' is a monovalent substituted or unsubstituted hydrocarbon radical R'' and R''' are independently hydrogen, monovalent substituted or unsubstituted hydrocarbon radical; and Y is selected from: Typical uses for the organofunctional silacyclobutanes of the invention are (a) endcapping silanol terminated polydiorganosiloxanes using compounds of the invention wherein R' is a monovalent substituted or unsubstituted hydrocarbon radical; (b) functionalizing siloxane resins containing silanol radicals by reacting the SiOH with the silacyclobutane Y group; and (c) functionalizing silica or glass surfaces by similarly introducing the silacyclobutane group. The following examples will serve to illustrate the silacyclobutanes of this invention and the claimed method of their manufacture. All parts and percentages in said examples and elsewhere in the specification and claims are by weight unless otherwise indicated. Example 1 1,1-Diacetoxysilacyclobutane To 30.0 g trimethylsilylacetate was added 16.0 g 1,1-dichlorosilacyclobutane. The reactants were stirred for one hour at 25°C. and fractional distillation performed on the reaction mixture. The title compound was isolated as a clear, colorless fluid. The yield was 14.6 g (81.4%). The structure of the product was confirmed by mass spectroscopy and nuclear magnetic resonance spectroscopy (NMR). Example 2 1,1-Diformatosilacyclobutane An admixture of 0.56 g 1,1-dichlorosilacyclobutane and 1.01 g dimethylvinylsilylformate gave a clear mixture with a mild exotherm. The product was identified by mass spectroscopy. Example 3 1-Acetoxy-1-methylsilacyclobutane An admixture of 19.9 g 1-chloro-1-methylsilacyclobutane and 26.0 g trimethylsilylacetate gave a clear solution. By-product trimethylchlorosilane was immediately distilled over at room temperature and the solution allowed to cool. The title compound was distilled at reduced pressure. The boiling point was 90-93.5°C. at 108 mm Hg. The yield was 17.1 g (77%). The product was identified by NMR and mass spectroscopy. Example 4 1,1-Bis(methylethylketoximo)silacyclobutane When, in accordance with the general procedure of Example 1, 1,1-dichlorosilacyclobutane and methylvinylbis(methylethylketoximo)silane are reacted together it is predicted that the title compound is formed. Example 5 1-Methyl-1-(methylethylketoximo)silacyclobutane In accordance with the general procedure of Example 1, when 1-chloro-1-methylsilacyclobutane and methylvinylbis(methylethylketoximo)silane are reacted it is predicted that the title compound is formed. Example 6 1,1-Bis(diethylaminoxy)silacyclobutane In accordance with the general procedure of Example 1, when 1,1-dichlorosilacyclobutane and methylvinylbis(diethylaminoxy)silane are reacted it is predicted that the title compound is formed. Example 7 1-Methyl-1-(diethylaminoxy)silacyclobutane In accordance with the general procedure of Example 1, when 1-chloro-1-methylsilacyclobutane and methylvinylbis(diethylaminoxy)silane are reacted it is predicted that the title compound is formed. Example 8 1,1-Diacetoxy-3-methylsilacyclobutane In accordance with the general procedure of Example 1, when 1,1-dichloro-3-methylsilacyclobutane and trimethylsilylacetate are reacted, it is predicted that the title compound is obtained. Example 9 1,1-Bis(isopropenoxy)silacyclobutane In accordance with the general procedure of Example 1, when 1,1-dichlorosilacyclobutane and isopropenoxytrimethylsilane are reacted, it is predicted that the title compound is obtained. Example 10 1-Methyl-1-(isopropenoxy)silacyclobutane In accordance with the general procedure of Example 1, when 1-chloro-1-methylsilacyclobutane and isopropenoxytrimethylsilane are reacted, it is predicted that the title compound is obtained. Example 11 To a mixture of 75.0 g of HO(Me₂SiO) x H (0.23 percent by weight hydroxyl radical), 3.16 g of triethylamine and 10.2 g of anhydrous magnesium sulfate in 227 g diethyl ether was added 1.53 ml 1-acetoxy-1-methylsilacyclobutane. The mixture was stirred 48 hours, filtered and stripped to 73°C. at 0.6 mm Hg to give 73.5 g of clear colorless polymer. Example 12 To a mixture of 152.3 g HO(Me₂SiO) x H (about 0.14 percent by weight hydroxyl radical, Mw of about 50,000 and Mn of about 24,000) and 15.3 g anhydrous magnesium sulfate in 352 g diethyl ether was added a solution of 0.197 g 1-acetoxy-1-methylsilacylobutane and 1.15 g 1,1-diacetoxysilacyclobuane in 50 ml diethyl ether. The mixture was stirred for 3 hours, filtered and stripped to 75°C. and 1.5 mm Hg to give 149.2 g clear colorless polymer. The weight average molecular weight (Mw) was 340,000 and the number average molecular weight (Mn) was 88,000 to give a Mw/Mn ratio of 3.9. Example 13 When 1.72 g of trimethylsilylacetamide was mixed with 0.92 g of 1,1-dichlorosilacyclobutane in 5 g of methylene chloride, a white precipitate formed. The precipitate dissolved upon shaking and slowly recrystallized as white needles. There was no trimethylchlorosilane detected in the residual fluid, indicating that the expected reaction to form 1,1-diacetamidosilacyclobutane did not occur.

Claims: A process for preparing a silacyclobutane of the formula in accordance with the reaction wherein A is a monovalent substituted or unsubstituted hydrocarbon radical or halogen; Hal is a halogen; R is a monovalent Substituted or unsubstituted hydrocarbon radical; R' is a monovalent substituted or unsubstituted hydrocarbon radical if A is a monovalent substituted or unsubstituted hydrocarbon radical; R' is a Y group if A is a halogen; R'' and R''' are independently hydrogen, monovalent substituted or unsubstituted hydrocarbon radical; Y is selected from: and x is an integer of from 0 through 3. Compounds of the formula wherein R' is a monovalent substituted or unsubstituted hydrocarbon radical ; R'' and R''' are independently hydrogen, monovalent substituted or unsubstituted hydrocarbon radicals; and Y is selected from:

Inventors: BANEY RONALD HOWARD, BILGRIEN CARL JOSEPH, FIEDLER LAWRENCE DALE, LEE CHI-LONG, BANEY, RONALD HOWARD, BILGRIEN, CARL JOSEPH, FIEDLER, LAWRENCE DALE, LEE, CHI-LONG
Applicants: DOW CORNING, DOW CORNING CORPORATION
Application year: 1990
Main classification: C07F7
IPC codes: C07F7