[18156-74-6]  · C6H12N2Si  · N-(Trimethylsilyl)imidazole  · (MW 140.29)

(silylating agent for alcohols and 1,3-dicarbonyl compounds;2 reaction with esters to give imidazolides; preparation of O-trimethylsilyl monothioacetals; aromatization of the A-ring of steroids)

Physical Data: bp 93-94 °C/14 mmHg; fp 5 °C; d 0.956 g cm-3.

Form Supplied in: liquid.

Handling, Storage, and Precautions: flammable. Harmful by inhalation, in contact with skin, and if swallowed. Possible carcinogen. Use in a fume hood. When using, wear protective gear and clothing. Handle and store under N2. Store in a cool dry place.

General Discussion.

N-(Trimethylsilyl)imidazole is a powerful silylating agent for alcohols (eq 1).2 1,3-Dicarbonyl compounds, although usually existing mostly in the enol form, are not efficiently silylated by standard methods. N-(Trimethylsilyl)imidazole has proved to be an ideal reagent for this transformation (eq 2).3

N-(Trimethylsilyl)imidazole reacts with phenyl and 2,2,2-trifluoroethyl esters under base catalysis to give acylimidazolides (eq 3).4 These imidazolides show reactivity similar to acyl chlorides and therefore are useful in synthesis.5

N-(Trimethylsilyl)imidazole is used in the preparation of O-trimethylsilyl monothioacetals directly from corresponding carbonyl compounds and thiols (eq 4).6 The basicity of the medium due to the imidazole generated during the reaction effectively prevents dithioacetalation.

Aromatization of the A-ring of steroid systems has been achieved by the use of N-(trimethylsilyl)imidazole (eq 5).7

1. For reviews on silylations, see: (a) Birkofer, L.; Ritter, A. AG(E) 1965, 4, 417. (b) Klebe, J. F. ACR 1970, 3, 299. (c) Colvin, E. W. CSR 1978, 7, 15. (d) Cooper, B. E. CI(L) 1978, 794. (e) Fleming, I. CSR 1981, 10, 83. (f) Lalonde, M.; Chan, T. H. S 1985, 817.
2. Kerwin, S. M.; Paul, A. G.; Heathcock, C. H. JOC 1987, 52, 1686.
3. Zhou, Y. F.; Huang, N. Z. SC 1982, 12, 795.
4. Bates, G. S.; Diakur, J.; Masamune, S. TL 1976, 4423.
5. Staab, H. A. AG(E) 1962, 1, 351.
6. Sassaman, M. B.; Surya Prakash, G. K.; Olah, G. A. S 1990, 104.
7. Kulkarni, S.; Abdel-Baky, S.; Le Quesne, P. W.; Vouros, P. Steroids 1989, 53, 131.

Janet Wisniewski Grissom & Gamini Gunawardena

University of Utah, Salt Lake City, UT, USA

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