Dichlorodimethylsilane1

Me2SiCl2

[75-78-5]  · C2H6Cl2Si  · Dichlorodimethylsilane  · (MW 129.06)

(additive for pinacol cyclization;2 protecting group for diols3 and carbonyl compounds;4 precursor for a wide variety of silicon-based reagents)

Physical Data: mp -76 °C; bp 70-71 °C; d 1.064 g cm-3.

Solubility: sol chlorinated solvents and ethereal solvents; reacts with protic solvents.

Form Supplied in: liquid form from laboratory to commercial scale (typical purities >95%).

Purification: can be purified by distillation.

Handling, Storage, and Precautions: reacts with water, amines, alcohols, amides, and other protic species with the evolution of hydrogen chloride. Use in a fume hood.

Pinacol Reaction.

Dichlorodimethylsilane (1) allows clean pinacol cyclization of a keto aldehyde to occur without competition from an aldol reaction (eq 1).2

Protection.

The success of the pinacol cyclization is due to the formation of a siliconide, the silicon equivalent of an acetonide. Reaction of a diol with (1) in the presence of base also provides these cyclic silicon compounds (eq 2).3,5 However, the labile dimethylsiliconide does not afford a widely applicable form of protection for this functional group, although it has found some use with pericyclic reactions.6

Enolates derived from aldehydes can also form bisenol ethers with (1), but the reaction fails with aldehydes containing four or fewer carbons.7 Ketone lithium enolates provide bisenol ethers in good yields when treated with (1). These bisenol ethers can then be employed in further reactions such as intramolecular aldol reactions.8 The formation of bisenol ethers by treatment of ketones with the silyl dichloride (1) in the presence of Triethylamine and Sodium Iodide has been advocated. However, the yields can still be variable and the use of N,N-diethylaminodimethylchlorosilane is suggested as a superior silylating agent.4 The lithium enolate derived from pinacolone reacts with an equivalent of (1) to provide the monoenol silyl chloride that can then be treated with a wide variety of oxygen and nitrogen based nucleophiles.9 Chiral enol ethers are also available through the use of the dichloride (1) as the silicon source (eq 3).10

Silanes.

Dichlorodimethylsilane (1) is a precursor to a wide variety of silicon reagents. For example, reaction with an organometallic reagent, such as phenyl- or t-butyllithium, results in the corresponding silyl chloride (eq 4).11 Many of these silyl chlorides have found application for the protection of functional groups.12

The presence of two leaving groups allows for the introduction of two different nucleophilic species.13 In addition to carbon, heteroatom nucleophiles have been used.14 A wide variety of heterocyclic derivatives are available when difunctional, nucleophilic compounds are treated with (1) (eq 5).15 The synthetic potential of all of these derivatives is as wide as organosilicon chemistry.16

The dichloride (1) has also found widespread application for the formation of polysiloxanes and other high molecular weight silanes.17 In addition to water, the chlorine atoms can be displaced by a wide variety of nucleophiles to provide some useful reagents, such as dimethyldiacetoxysilane.18

A controlled reaction of dichloride (1) with lithium in THF affords dodecamethylsilane,19 a reagent that has been used for the preparation of silyl enol ethers through photolytic cleavage.20 Silanes and polysilanes are readily available from the addition of an organometallic species to (1). Thus the bisvinylsilane (2) can be prepared from (1) (eq 6).21

Related Reagents.

Di-t-butyldichlorosilane; Di-t-butylsilyl Bis(trifluoromethanesulfonate).


1. Colvin, E. W. Silicon in Organic Synthesis; Butterworths: London, 1981.
2. Corey, E. J.; Carney, R. L. JACS 1971, 93, 7318.
3. Kelly, R. W. TL 1969, 967.
4. Rathke, M. W.; Weipert, P. D. SC 1991, 21, 1337.
5. Cragg, R. H.; Lane, R. D. JOM 1985, 289, 23.
6. (a) Jenneskens, L. W.; Kostermans, G. B. M.; Harmannus, J. B.; De Wolf, W. H.; Bickelhaupt, F. JCS(P1) 1985, 2119. (b) Kita, Y.; Okunaka, R.; Honda, T.; Shindo, M.; Tamura, O. TL 1989, 30, 3995.
7. Fataftah, Z. A.; Ibrahim, M. R.; Abdel-Rahman, H. N. BCJ 1991, 64, 671.
8. Fataftah, Z. A.; Ibrahim, M. R.; Abu-Agil, M. S. TL 1986, 27, 4067.
9. Walkup, R. D. TL 1987, 28, 511.
10. (a) Kaye, P. T.; Learmonth, R. A. SC 1989, 19, 2337. (b) Walkup, R. D.; Obeyesekere, N. H. JOC 1988, 53, 920.
11. (a) Benkeser, R. A.; Foster, D. J. JACS 1952, 74, 5314. (b) Sommer, L. H.; Tyler, L. J. JACS 1954, 54, 1030.
12. Corey, E. J.; Venkateswarlu, A. JACS 1972, 94, 6190.
13. (a) Gillard, J. W.; Fortin, R.; Morton, H. E.; Yoakim, C.; Quesnelle, C. A.; Daignault, S.; Guindon, Y. JOC 1988, 53, 2602. (b) Barluenga, J.; Foubelo, F.; Gonzalez, R.; Fananas, F. J.; Yus, M. CC 1991, 1001.
14. (a) Wei, Z. Y.; Wang, D.; Li, J. S.; Chan, T. H. JOC 1989, 54, 5768. (b) Tamao, K.; Nakajo, E.; Ito, Y. T 1988, 44, 3997. (c) Wei, Z. Y.; Li, J. S.; Wang, D.; Chan, T. H. TL 1987, 28, 3441.
15. (a) Yamamoto, Y.; Takeda, Y.; Akiba, K. TL 1989, 30, 725; Nifant'ev, I. E.; Yarnykh, V. L.; Borzov, M. V.; Mazurchik, B. A.; Mstislavskii, V. I.; Roznyatovskii, V. A.; Ustynyuk, Y. A. OM 1991, 10, 3739. (b) Roesky, H. W.; Meller-Rehbein, B.; Noltemeyer, M. ZN(B) 1991, 46, 1053. (c) Barluenga, J.; Tomas, M.; Ballesteros, A.; Gotor, V. S 1987, 489.
16. Tamao, K.; Nakajo, E.; Ito, Y. JOC 1987, 52.
17. Pawlenko, S. Organosilicon Chemistry; de Gruyter: Berlin, 1986.
18. (a) Kelly, R. W. J. Chromatogr. 1969, 43, 229. (b) Matyjaszewski, K.; Chen, Y. L. JOM 1988, 340, 7.
19. (a) Gilman, H.; Tomasi, R. A. JOC 1963, 28, 1651. (b) Krasnova, T. L.; Mudrova, N. A.; Bochkarev, V. N.; Kisin, A. V. ZOB 1985, 55, 1528. (c) Cen, S. M.; Katti, A.; Blinka, T. A.; West, R. S 1985, 684.
20. (a) Ishikawa, M.; Kumada, M. JOM 1972, 42, 325. (b) Ando, W.; Ikeno, M. CL 1978, 609.
21. Nativi, C.; Perrotta, E.; Ricci, A.; Taddei, M. TL 1991, 32, 2265.

David J. Ager

The NutraSweet Company, Mount Prospect, IL, USA



Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.