[75-79-6]  · CH3Cl3Si  · Methyltrichlorosilane  · (MW 149.48)

(precursor to organosilicon compounds;1 silylating agent;1 Lewis acid2)

Physical Data: bp 66 °C; d 1.273 g cm-3.

Solubility: sol methylene chloride.

Form Supplied in: liquid; commercially available.

Purification: can be purified by distillation.

Handling, Storage, and Precautions: is corrosive and moisture sensitive. It should be handled in an anhydrous atmosphere in a fume hood.

Organosilicon Compounds.

MeSiCl3 is an important precursor to organosilicon compounds.1 It reacts with carbanions to form corresponding alkyl(aryl) methylsilanes.3 Grignard and organolithium reagents are the most frequently used carbanion sources in this transformation. Generally, the organolithiums are preferred over Grignard reagents, especially in the preparation of tetraorganosilanes. However, it was reported that the reaction using Grignard reagents was facilitated by a catalytic amount of cyanide or thiocyanate ions.4 Stepwise substitution on MeSiCl3 can be accomplished by introducing carbanions sequentially, yielding dichloro-, monochloro-, and tetraorganosilanes, respectively (eq 1). This makes it possible to design a silane with a specific steric bulkiness, a feature often required for the monochlorosilanes to serve as protecting groups.5

MeSiCl3 has been used as a coupling agent in the preparation of the multidentate ligand (RRR)-siliphos {(RRR)-MeSi[CH2P(t-Bu)Ph]3} (eq 2).6 The preparation of this optically pure tristertiary phosphine was achieved by deprotonation of optically pure (R)-P(BH3)Me(t-Bu)Ph, followed by silylation of the resulting carbanion with MeSiCl3, and the subsequent removal of the BH3 protecting group with Morpholine. The function of MeSiCl3 as a coupling agent has also been widely used for the synthesis of star-branched polymers.7 Cyclic silanes are obtained by treating MeSiCl3 with dicarbanions and tricarbanions, albeit in lower yields (eqs 3 and 4).8 Treatment of CFCl3/(Et2N)3P with MeSiCl3 led to the formation of CFCl2SiCl2Me.9

Substitutions of MeSiCl3 can also be performed under radical conditions or with transition metal catalysis.1,10 The radical reactions can be initiated either by higher temperature or photolysis. However, the selectivity of the reaction is generally poor.1 Better results were obtained with transition metal-catalyzed reactions. It was reported that MeSiCl3 reacted with terminal alkynes in the presence of a catalytic amount of Copper(I) Chloride to form alkynyldichlorosilanes (eq 5).11

Besides C-silylation, MeSiCl3 is also capable of silylating heteroatoms such as, O, N, and S.1 It reacts with alcohols, oximes, alkoxysilanes, and esters to form corresponding silylated products.12 In fact, certain poly- or oligoorganosiloxanes were prepared from MeSiCl3 and hydroxy-containing compounds.13 When aldehydes and ketones are used, tris(alkenyloxy)silanes are obtained in good yields (eq 6).14 In the case of 1,3-diketones, organosilicon(IV) b-diketonate complexes are formed (eq 7).15 Amines are silylated in a similar fashion.16

Reactions as a Lewis Acid.

MeSiCl3 is an effective Lewis acid in the condensation of carboxylic acids with alcohols and amines.17 Good yields of esters and amides are obtained. MeSiCl3 reacts with epoxides to form b-chloroalkoxysilanes in good yields.18 It also promotes the addition of allylstannanes to aldehydes (eq 8).19 Compared to the traditional Lewis acids, MeSiCl3 is relatively mild and less moisture sensitive. The reaction is very selective. When both allylstannanes and allylsilanes are present in the reaction, aldehydes react only with allylstannanes. It was reported that acetylacetone was condensed to pyrylium chloride by using MeSiCl3.20

MeSiCl3 cleaves the ether linkage of gem-amino ethers to form dialkyl(methylene)ammonium chloride (Mannich-type salts) in excellent yields (eq 9).21a This procedure is much more convenient, efficient, economical, and less dangerous compared to earlier methods. The Mannich salts were also prepared in situ for electrophilic substitution of nucleophilic aromatic compounds (eq 10).21b,c

In conjunction with CuCl, MeSiCl3 promotes conjugate addition of both organomagnesium and manganese(II) reagents to a,b-ethylenic esters (eq 11).22 These are much higher yield reactions compared to conjugate addition of copper or cuprate reagents to the substrates. The exact role of MeSiCl3 in the reactions is not clear.

MeSiCl3 has been found useful as a deprotecting agent in peptide chemistry.23 It also promotes, in conjunction with diphenyl sulfoxide, formation of disulfide bonds in peptides (eq 12).24

MeSiCl3/Sodium Iodide2 is an equivalent of Iodotrimethylsilane,25 a widely used silicon Lewis acid, which has been used for various organic transformations. Compared to Me3SiI, MeSiCl3/NaI is milder, and thus it is more regioselective when used in ether cleavage (eq 13). Methyl ethers (ROMe) are cleaved affording alcohols as sole products, provided that the alkyl groups are either primary or secondary. Benzyl, trityl, and tetrahydropyranyl ethers are also cleaved regioselectively at ambient temperature to give quantitative yields of alcohols. If a tertiary alkyl group is present in the ethers, an alkyl iodide is then obtained. Esters and lactones are similarly cleaved to carboxylic acids. Acetals are converted to carbonyl compounds by MeSiCl3/NaI (eq 14).

MeSiCl3/NaI is a good iodinating agent, which converts alcohols to corresponding iodides (eq 15). Primary alcohols react very slowly even under reflux conditions, giving low yields. However, moderate and excellent yields of alkyl iodides can be obtained with secondary, tertiary, and benzylic alcohols.

MeSiCl3/NaI was found to dehalogenate a-halo ketones reductively (eq 16). The conversion of 5-cyano-7-oxabicyclo[2.2.1]hept-2-ene to 2-furanpropanenitrile was also reported (eq 17).26

1. Voorhoeve, R. J. H. Organohalosilanes, Precursors to Silicones; Elsevier: Amsterdam, 1967.
2. (a) Olah, G. A.; Husain, A.; Singh, B. P.; Mehrotra, A. K. JOC 1983, 48, 3667. (b) Olah, G. A.; Husain, A.; Gupta, B. G. B.; Narang, S. C. AG(E) 1981, 20, 690.
3. (a) Rubinazztajn, S.; Zeldin, M.; Fife, W. K. Synth. React. Inorg. Met. Org. Chem. 1990, 20, 495. (b) Van den Ancker, T.; Jolly, B. S.; Lappert, M. F.; Raston, C. L.; Skelton, B. W.; White, A. H. CC 1990, 1006. (c) Chen, G. J.; Tamborski, C. JOM 1985, 293, 313. (d) Tamborski, C.; Chen, G. J.; Anderson, D. R.; Snyder, Jr., C. E. Ind. Eng. Chem., Prod. Res. Dev. 1983, 22, 172. (e) Erchak, N. P.; Ashmane, A. R.; Popelis, Y. Y.; Lukevits, E. JGU 1983, 53, 334 (CA 1983, 99, 53 874p). (f) Shi, B. C.; Jutzi, P. Chem. J. Chin. Univ. 1991, 12, 1338 (CA 1992, 117, 212 575a). (g) Wada, M.; Wakamori, H.; Hiraiwa, A.; Erabi, T. BCJ 1992, 65, 1389.
4. Lennon, P. J.; Mack, D. P.; Thompson, Q. E. OM 1989, 8, 1121.
5. Toshima, K.; Tatsuta, K.; Kinoshita, M. BCJ 1988, 61, 2369.
6. Ward, T. R.; Venanzi, L. M.; Albinati, A.; Lianza, F.; Gerfin, T.; Gramlich, V.; Tombo, G. M. R. HCA 1991, 74, 983.
7. For example, see: (a) Storey, R. F.; George, S. E.; Nelson, M. E. Macromolecules 1991, 24, 2920. (b) Jenkins, D. K. Polymer 1985, 26, 147. (c) Hadjichristidis, N.; Roovers, J. Polymer 1985, 26, 1087.
8. (a) Luchina, N.; Ciobanu, A.; Bostan, M. RRC 1981, 26, 1479. (b) Boudjouk, P.; Sooriyakumaran, R.; Kapfer, C. A. JOM 1985, 281, C21. (c) Jurkschat, K.; Mugge, C.; Schmidt, J.; Tzschach, A. JOM 1985, 287, C1.
9. Josten, R.; Ruppert, I. JOM 1987, 329, 313.
10. Son, V. V.; Ivashchenko, S. P.; Son, T. V. JGU 1990, 60, 624 (CA 1990, 113, 78 480c).
11. Deleris, G.; Dunogues, J.; Calas, R.; Lapouyade, P. JOM 1974, 80, C45.
12. (a) Fomin, V. A.; Etlis, V. S.; Petrukhin, I. V. JGU 1983, 53, 711 (CA 1983, 99, 105 322d). (b) Ryasin, G. V.; Fedotov, I. S.; Luk'yanova, I. A.; Mironov, V. F. J. Appl. Chem. USSR 1974, 47, 2683 (CA 1975, 82, 43 513e). (c) Voronkov, M. G.; Kuznetsova, G. A.; Baryshok, V. P. JGU 1983, 53, 1512 (CA 1983, 99, 212 600q). (d) Mbah, G.; Speier, J. L. JOM 1984, 271, 77.
13. For example, see: (a) Martynova, T. N.; Chupakhina, T. I. JOM 1988, 345, 11. (b) Rebrov, E. A.; Muzafarov, A. M.; Papkov, V. S.; Zhdanov, A. A. DOK 1989, 309, 376 (CA 1990, 112, 235 956m). (c) Andrianov, K. A.; Chernyavskii, A. I.; Makarova, N. N. IZV 1979, 1835 (CA 1980, 92, 42 027u).
14. (a) Shchepin, V. V.; Lapkin, I. I. JGU 1981, 51, 1957 (CA 1982, 96, 52 374b). (b) Rochin, C.; Babot, O.; Moulines, F.; Duboudin, F. JOM 1984, 273, C7. (c) Rochin, C.; Babot, O.; Duboudin, F. JOM 1985, 281, C24.
15. (a) Schott, V. G.; Golz, K. Z. Anorg. Allg. Chem. 1973, 399, 7. (b) Serpone, N.; Hersh, K. A. JOM 1975, 84, 177.
16. (a) Issleib, K.; Kuhne, U.; Krech, F. PS 1985, 21, 367. (b) tom Dieck, H.; Zettlitzer, M. CB 1987, 120, 795. (c) Brauer, D. J.; Burger, H.; Liewald, G. R.; Wilke, J. JOM 1985, 287, 305. (d) Grobe, J.; Voulgarakis, N. Z. Anorg. Allg. Chem. 1984, 517, 125. (e) Grobe, J.; Hildebrandt, W.; Martin, R.; Walter, A. Z. Anorg. Allg. Chem. 1991, 592, 121.
17. (a) Nakao, R.; Oka, K.; Fukumoto, T. BCJ 1981, 54, 1267. (b) Akpoyraz, M. Doga, Ser. C 1980, 4(2), 1 (CA 1982, 96, 103 600g).
18. Viktorova, I. P.; Gladkikh, A. F.; Viktorov, O. F. JGU 1976, 46, 1947 (CA 1977, 86, 155 731p).
19. Marshall, R. L.; Young, D. J. TL 1992, 33, 1365.
20. Serpone, N.; Ignacz, T. F. G 1985, 115, 419.
21. (a) Rochin, C.; Babot, O.; Dunogues, J.; Duboudin, F. S 1986, 228. (b) Heaney, H.; Papageorgiou, G.; Wilkins, R. F. CC 1988, 1161. (c) Fairhurst, R. A.; Heaney, H.; Papageorgiou, G.; Wilkins, R. F.; Eyley, S. C. TL 1989, 30, 1433.
22. (a) Cahiez, G.; Alami, M. TL 1990, 31, 7423. (b) Cahiez, G.; Alami, M. TL 1990, 31, 7425.
23. Kiso, Y.; Yoshida, M.; Fujisaki, T.; Mimoto, T.; Kimura, T.; Shimokura, M. Proc. 24th Symp. Peptide Chem.; Protein Research Foundation: Osaka, 1986; p 205 (CA 1988, 108, 112 924j).
24. (a) Akaji, K.; Tatsumi, T.; Yoshida, M.; Kimura, T.; Fujiwara, Y.; Kiso, Y. JACS 1992, 114, 4137. (b) Akaji, K.; Tatsumi, T.; Yoshida, M.; Kimura, T.; Fujiwara, Y.; Kiso, Y. CC 1991, 167.
25. Olah, G. A.; Prakash, G. K. S.; Krishnamurti, R. In Advances in Silicon Chemistry; Larson, G. L. Ed; JAI Press: Greenwich, CT, 1991; Vol. 1, p 1.
26. Kibayashi, T.; Ishii, Y.; Ogawa, M. BCJ 1985, 58, 3627.

George A. Olah, G. K. Surya Prakash, Qi Wang & Xing-ya Li

University of Southern California, Los Angeles, CA, USA

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