Yield:-

Reaction Conditions:

ethylene dibromide in diethyl ether at 19.4 - 30;Product distribution / selectivity;Heating / reflux;Industry scale;Grignard Reaction;

Steps:

31; 33

3J I g Mg and of 6000 ml of diethyl ether (E?2θ) were loaded into the reactor at room temperature. 22ml of 1 ,2-Dibromoethane was then added to activate the Mg. Within 10 minutes, an exotherm was observed as well with vigorous Et₂O reflux and ethylene(CH₂=CH₂) evolution. The temperature rose from 20⁰C to 30⁰C. The Mg activation resulted in the formation of a hazy solution.[0029] A premixcd solution of 920 g of 1 ,4-dibromopentanc, 457 g of Mc2Si(OMe)2 and2353 ml ether was prepared and added drop wise to the already activated Mg in Et2θ. Thirty minutes after addition, a cloudy reaction mixture was observed which indicated the formation of MgBr(OMe) .salt. The reaction mixture reached a maximum exothermic temperature of 35.⁰C. At the end of the addition a milky, flowable reaction mixture was observed. Stirring was stopped to observe the phases in the system: the solid phase was readily precipitated. [003Of The crude reaction mixture was filtered through a 10-micron membrane filter to remove MgBr(OMe) salt and excess Mg. The resulting material was distilled to remove the ether. The distilled solution contained a large amount of white precipitate after most of the ether was removed, most likely due to MgBr(OMe) salt remaining in solution after filtration. After removing salt and ether, the solution was stripped under vacuum to remove high boilers. The stripped crude was loaded into a i -liter flask of a 36" long spinning band distillation column for final purification at ambient pressure. The spinning band column is composed of a spinning still made of tantalum wire cloth or Teflon. The distilled 1 , 1 - dimethyl-1-silacyclohexane had a purity of >99,92% and a total metal content of <500 ppb. Example 33. 254 g Mg and of 3000 ml of diethyl ether (Et2θ) were loaded into the reactor at room temperature. 15 ml of 1 ,2-Dibromoethane was then added to activate the Mg. Within 10 minutes the temperature rose from 19.4°C Io 29.7°C, and EI2O refluxed from the condenser, the Mg was activated and a hazy reaction mixture was observed. I] A premixed solution of 668 g Of MeSi(OFu)^, 750 g 1,5 dibromopeniane and 1767 ml ether was prepared and added to the already activated Mg in Et2θ over a 3 hour period. The reaction mixture reached an exothermic temperature of 33.5°C and the reaction was allowed to run overnight.USD5] GC analysis of the liquid phase a t=l 8 hours determined that the reaction to be: 79.9 area% methylethoxysilacyclohexane with 13.3 area% unreacfed MeSi(OEt)3 and 2.8 area% unreacied dibromopentane.

References:

WO2009/61581,2009,A1 Location in patent:Page/Page column 9-11