[994-30-9]  · C6H15ClSi  · Chlorotriethylsilane  · (MW 150.75)

(silylating agent, Lewis acid catalyst)

Alternate Name: triethylsilyl chloride.

Physical Data: bp 145-147 °C; d 0.898 g cm-3.

Solubility: readily sol most aprotic organic solvents, although CH2Cl2 is most commonly used; reacts with H2O and other protic solvents.

Form Supplied in: colorless liquid, or as a 1.0 M solution in THF.

Handling, Storage, and Precautions: should be handled and stored under an anhydrous, inert atmosphere.

General Considerations.

The triethylsilyl moiety is often used as a protecting group for alcohols because of its greater stability towards hydrolysis than the smaller trimethylsilyl group. Alcohols can normally be silylated with Et3SiCl using either Imidazole in DMF or Triethylamine/4-Dimethylaminopyridine in CH2Cl2 (eqs 1 and 2).1,2 For substrates which are more difficult to derivatize, it may be advantageous to carry out the reaction in neat Pyridine (eq 3)3 or to generate the alkoxide salt prior to the addition of Et3SiCl (eq 4).4-6

Silyl ethers have also been obtained by in situ trapping of an intermediate alkoxide that results from a nucleophilic addition onto an ester7 or epoxide8 (eqs 5 and 6).

Silyl enol ethers can be prepared from ketones by trapping the kinetically formed lithium enolate with Et3SiCl (eqs 7 and 8),9,10 or by the conjugate addition of a dialkylcuprate to an a,b-unsaturated ketone with silylation of the enolate intermediate (eq 9).11-13 Surprisingly, the addition of Lithium Di-n-butylcuprate to an a,b-unsaturated lactone in the presence of Et3SiCl resulted in the 1,4-addition of the triethylsilyl moiety, apparently via the in situ formation of an intermediate silylcuprate species (eq 10).14

Organolithium salts generally react with Et3SiCl to afford organosilanes. Schlessinger used a deprotonation-silylation procedure to introduce a triethylsilyl group at the a-position of an alkylimine (eq 11).15 A variety of other stabilized carbanions have been reported to react cleanly with Et3SiCl (eqs 12-15).16 -19

In a similar manner, aryl, vinyl-, and alkynylsilanes can be prepared by the reaction of the appropriate carbanion with Et3SiCl (eqs 16-21).20-25

Related Reagents.

t-Butyldimethylchlorosilane; Chlorotrimethylsilane; Chlorotriphenylsilane.

1. Corey, E. J.; Link, J. O. TL 1990, 31, 601.
2. Anderson, J. C.; Ley, S. V. TL 1990, 31, 431.
3. Hart, T. W.; Metcalfe, D. A.; Scheinmann, F. CC 1979, 156.
4. Hoffmann, R.; Brückner, R. CB 1992, 125, 1471.
5. Smith, A. B., III; Richmond, R. E. JACS 1983, 105, 575.
6. Andrews, D. R.; Barton, D. H. R.; Hesse, R. H.; Pechet, M. M. JOC 1986, 51, 4819.
7. Cooke, M. P., Jr. JOC 1986, 51, 951.
8. Andrews, G. C.; Crawford, T. C.; Contillo, L. G., Jr. TL 1981, 22, 3803.
9. (a) Sampson, P.; Hammond, G. B.; Wiemer, D. F. JOC 1986, 51, 4342. (b) Sampson, P.; Wiemer, D. F. CC 1985, 1746.
10. (a) Danishefsky, S. J.; Uang, B. J.; Quallich, G. JACS 1985, 107, 1285. (b) Danishefsky, S. J.; Harvey, D. F.; Quallich, G.; Uang, B. J. JOC 1984, 49, 392.
11. Horiguchi, Y.; Komatsu, M.; Kuwajima, I. TL 1989, 30, 7087.
12. Marino, J. P.; Emonds, M. V. M.; Stengel, P. J.; Oliveira, A. R. M.; Simonelli, F.; Ferreira, J. T. B. TL 1992, 33, 49.
13. (a) Ager, D. J.; Fleming, I.; Patel, S. K. JCS(P1) 1981, 2520; (b) Fleming, I.; Newton, T. W. JCS(P1) 1984, 1805.
14. Amberg, W; Seebach, D. AG(E) 1988, 27, 1718.
15. Schlessinger, R. H.; Poss, M. A.; Richardson, S.; Lin, P. TL 1985, 26, 2391.
16. Szymonifka, M. J.; Heck, J. V. TL 1989, 30, 2873.
17. Savignac, P.; Teulade, M.-P.; Collignon, N. JOM 1987, 323, 135.
18. Oppolzer, W.; Snowden, R. L.; Simmons, D. P. HCA 1981, 64, 2002.
19. Seyferth, D.; Mammarella, R. E.; Klein, H. A. JOM 1980, 194, 1.
20. Block, E.; Eswarakrishnan, V.; Gernon, M.; Ofori-Okai, G.; Saha, C.; Tang, K.; Zubieta, J. JACS 1989, 111, 658.
21. Lee, G. C. M.; Holmes, J. M.; Harcourt, D. A.; Garst, M. E. JOC 1992, 57, 3126.
22. Soderquist, J. A.; Lee, S.-J. H. T 1988, 44, 4033.
23. Schinzer, D. S 1989, 179.
24. Hiyama, T.; Nishide, K.; Obayashi, M. CL 1984, 1765.
25. Uchida, K.; Utimoto, K.; Nozaki, H. JOC 1976, 41, 2215.

Edward Turos

State University of New York at Buffalo, NY, USA

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