[87436-97-3]  · C9H14MgSi  · Dimethylphenylsilyl(methyl)magnesium  · (MW 174.63)

(silyl magnesiation of alkynes; synthesis of vinylsilanes; disilylation of alkynes)

Solubility: sol ethereal solvents (ether, THF, DME, etc.).

Form Supplied in: not commercially available. The reagent is best prepared and used immediately.

Analysis of Reagent Purity: a suitable analytical method is not available. The reagent must be prepared immediately after titration of dimethylphenylsilyllithium and methylmagnesium iodide.

Preparative Method: an ethereal solution of methylmagnesium iodide (1.0 equiv) is added to a THF solution of Dimethylphenylsilyllithium1 (1.0 equiv) at 0 °C under an argon atmosphere. The mixture is stirred for 15 min and the resulting dimethylphenylsilyl(methyl)magnesium is used directly for further reactions.

Handling, Storage, and Precautions: the reagent is sensitive to moisture and should be handled under a dry, inert atmosphere. The reagent must be used immediately after preparation.

Silylmagnesiation of Alkynic Compounds.

Platinum- or copper-catalyzed silylmagnesiation2,3 of 1-dodecyne followed by aqueous workup provides (E)-1-dimethylphenylsilyl-1-dodecene (eq 1), which has also been produced by stoichiometric silylcupration4 or silyltitanation.5 Electrophiles such as iodine, methyl iodide, and valeraldehyde react with the intermediate derived from PtCl2(P-n-Bu3)2-catalyzed silylmagnesiation of 1-dodecyne to give the corresponding functionalized alkenylsilanes (eq 2).

Silylmagnesiation of 1,2-alkadienes in the presence of a Copper(I) Iodide catalyst, followed by aqueous workup, produces exclusively 1-(dimethylphenylsilyl)-1-cycloalkenes in which a PhMe2Si group is attached to the central carbon of the allene (eq 3).6 The initial adducts can undergo an intramolecular cyclization when the R group is substituted at the terminal position by a leaving group, to provide cycloalkanes with a dimethylphenylsilylmethylene substituent (eqs 4 and 5).7

Synthesis of Vinylsilanes.

In the presence of a Pd catalyst, PhMe2SiMgMe converts enol phosphates into vinylsilanes (eq 6).8 The reagent, which is believed to be (PhMe2Si)3MnMgMe (prepared in situ from 3 equiv of PhMe2SiMgMe and Manganese(II) Chloride), also transforms alkenyl halides, alkenyl sulfides, or enol phosphates into vinylsilanes (eq 7).9

Disilylation of Alkynes.

Addition of 1-alkynes to the reagent (PhMe2Si)3MnMgMe affords (E,Z) mixtures of 1,2-bis(dimethylphenylsilyl)-1-alkenes (eq 8).10 Trimethylsilyl(methyl)magnesium in place of PhMe2SiMgMe gives the corresponding disilylation product. The reaction can be successfully applied to the synthesis of highly strained tetrakis(trimethylsilyl)ethylene (eq 9).

1. (a) Gilman, H.; Lichtenwalter, G. D. JACS 1958, 80, 607. (b) George, M. V.; Peterson, D. J.; Gilman, H. JACS 1960, 82, 403.
2. Hayami, H.; Sato, M.; Kanemoto, S.; Morizawa, Y.; Oshima, K.; Nozaki, H. JACS 1983, 105, 4491.
3. CuCN-catalyzed silylzincation of 1-dodecyne with PhMe2SiZn-t-Bu2Li provides regioisomeric 2-dimethylphenylsilyl-1-dodecene exclusively. Okuda, Y.; Wakamatsu, K.; Tückmantel, W.; Oshima, K.; Nozaki, H. TL 1985, 26, 4629; Wakamatsu, K.; Nonaka, T.; Okuda, Y.; Tückmantel, W.; Oshima, K.; Utimoto, K.; Nozaki, H. T 1986, 42, 4427.
4. Fleming, I.; Newton, T. W. Roessler, F. JCS(P1) 1981, 2527.
5. Tamao, K.; Akita, M.; Kanatani, R.; Ishida, N.; Kumada, M. JOM 1982, 226, C9.
6. Morizawa, Y.; Oda, H.; Oshima, K.; Nozaki, H. TL 1984, 25, 1163.
7. Okuda, Y.; Morizawa, Y.; Oshima, K.; Nozaki, H. TL 1984, 25, 2483.
8. Okuda, Y.; Sato, M.; Oshima, K.; Nozaki, H. TL 1983, 24, 2015.
9. Fugami, K.; Oshima, K.; Utimoto, K. Nozaki, H. TL 1986, 27, 2161.
10. (a) Hibino, J.-I. Nakatsukasa, S.; Fugami, K.; Matsubara, S.; Oshima, K.; Nozaki, H. JACS 1985, 107, 6416. (b) Fugami, K.; Hibino, J.-I.; Nakatsukasa, S.; Matsubara, S.; Oshima, K.; Utimoto, K.; Nozaki, H. T 1988, 44, 4277.

Koichiro Oshima

Kyoto University, Japan

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