[7351-44-2]  · C11H27NSi3  · Tris(trimethylsilyl)ketenimine  · (MW 257.66)

(reactions with aldehydes; selective synthesis of (Z)-2-alkenenitriles and (E)-2-(1-hydroxyalkyl)-2-alkenenitriles)

Physical Data: bp 94-96 °C/19 mmHg.

Solubility: sol ether, THF; modestly sol aprotic solvents; reacts with H2O and protic solvents.

Form Supplied in: colorless oil.

Analysis of Reagent Purity: IR nfilmmax 2050, 1410, 1260, 840 cm-1. 1H NMR (CCl4) d 0.09 (s, 18 H), 0.19 (s, 9 H).

Preparative Methods: to a solution of Trimethylsilylacetonitrile2 (3.01 g, 26.6 mmol) in dry diethyl ether (40 mL) is added n-Butyllithium (10 % w/v in hexane, 38 mL, 59.3 mmol) at -60 °C and stirring is continued for 0.5 h. Chlorotrimethylsilane (7.48 g, 68.9 mmol) is slowly added and the mixture is allowed to warm to room temperature. The mixture is concentrated and distilled at bp 94-96 °C/19 mmHg to give tris(trimethylsilyl)ketenimine (5.67 g, 83%).

Purification: distill under reduced pressure.

Handling, Storage, and Precautions: bottles of tris(trimethylsilyl)ketenimine should be kept tightly sealed to preclude contact with moisture.

General Discussion.

Tris(trimethylsilyl)ketenimine (1) reacts with aldehydes in the presence of Boron Trifluoride Etherate at room temperature in benzene3 or dichloromethane to give a 1:1 adduct.4 Upon heating, the adduct is converted quantitatively into (E)-2-trimethylsilyl-2-alkenenitriles (2) (eq 1).

Compound (2) is desilylated in an alkaline medium to give pure (Z)-2-alkenenitriles (3) (eq 2).3 Several examples are summarized in Table 1.

Compound (2) also reacts with carbonyl compounds in the presence of Tetra-n-butylammonium Fluoride (TBAF) to give (E)-2-(1-hydroxyalkyl)-2-alkenenitriles (4) (eq 3).5 Several examples of this reaction are provided in Table 2.

1. Gornowicz, G. A.; West, R. JACS 1971, 93, 1714.
2. Matsuda, I.; Murata, S.; Ishii, Y. JCS(P1) 1979, 26.
3. Sato, Y.; Niinomi, Y. CC 1982, 56.
4. Matsuda, I.; Okada, H.; Izumi, Y. BCJ 1983, 56, 528.
5. Sato, Y.; Hitomi, K. CC 1983, 170.

Yoshiro Sato

Nagoya City University, Japan

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