Reaction #1435686

Reaction equation

magnesium

TEOS

1,4-dibromobenzene

iodine

→

1,4-bis(triethoxysilyl)benzene

Yield 43.0%

Solvents

THF

THF

THF

Conditions

Workup

1. 1
   Otherwere placed under nitrogen in a 1 L three-neck round bottom flask
2. 2
   Otherequipped with magnetic stir bar, condenser, and addition funnel
3. 3
   Temperatureto reflux
4. 4
   workup.ADDITIONthe addition
5. 5
   Temperatureat reflux for 1 h
6. 6
   Otherwas removed in vacuo
7. 7
   workup.ADDITIONHexane (200 mL) was added
8. 8
   Otherto precipitate any remaining magnesium salts in solution
9. 9
   Filtrationthe mixture was quickly filtered under nitrogen
10. 10
    Otherto produce a clear, light brown solution
11. 11
    OtherHexane was removed in vacuo
12. 12
    workup.DISTILLATIONThe product was purified by fractional distillation
13. 13
    OtherThe product was recovered as a clear liquid at 130–5° C. (0.2 mmHg) in 43–47% yield

Procedure

A mixture of magnesium turnings (15 g) and TEOS (450 mL, 2 mol) in THF (300 mL) were placed under nitrogen in a 1 L three-neck round bottom flask equipped with magnetic stir bar, condenser, and addition funnel. A small crystal of iodine was added and the mixture was brought to reflux. A solution of 1,4-dibromobenzene (48 g, 204 mmol) in THF (100 mL) was added dropwise over 2 h. Within 30 min of initiating the addition, the reaction became mildly exothermic. The reaction mixture was kept at reflux for 1 h after the completion of the addition of dibromide. The gray-green mixture was allowed to cool to room temperature before the THF was removed in vacuo. Hexane (200 mL) was added to precipitate any remaining magnesium salts in solution and the mixture was quickly filtered under nitrogen to produce a clear, light brown solution. Hexane was removed in vacuo. The product was purified by fractional distillation. The product was recovered as a clear liquid at 130–5° C. (0.2 mmHg) in 43–47% yield. 1H NMR (500 MHz, CDCl3) δ 7.67 (s, 4H, ArH), 3.86 (q, J=7.00 Hz, 12H, OCH2CH3), 1.23 (t, J=7.00 Hz, 18H, ArH); 13C NMR (125 MHz, CDCl3) δ 133.25,57.98, 17.43; 29Si NMR (99 MHz, CDCl3) δ−58.25; MS m/e calc'd for CI (M) C18H34Si2O6: 402.1894, found 402.1886.

Source