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Synlett 2002(11): 1919-1921
DOI: 10.1055/s-2002-34898
LETTER
© Georg Thieme Verlag Stuttgart · New York

2-Norbornyldimethylsilyl Ethers (NDMS): A New Protecting Group for Alcohols and Carboxylic Acids

Dieter K. Heldmann*, Jürgen Stohrer, Rafael Zauner
Consortium für elektrochemische Industrie GmbH, Central Research Company of Wacker-Chemie GmbH, Zielstattstraße 20, 81379 München, Germany
Fax: +49(89)74844242; e-Mail: dieter.heldmann@wacker.com ;
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Publication History

Received 6 August 2002
Publication Date:
21 October 2002 (online)

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Abstract

The use of the readily available 2-norbornyldimethylsilyl group (NDMS) in the protection of alcohols and carboxylic acids is described. Stabilities of the corresponding silyl compounds towards various reagents and deprotection conditions are compared with tert-butyldimethylsilyl-, iso-propyldimethyl and trimethylsilyl groups.

Key words

silicon - protecting groups - ethers - esters - hydrosilylation

    References

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7

Depending on the catalyst batch, ratios of 93:7 up to 95:5 were obtained. Major isomer is 3a(exo) according to citation 6.

8

All silylethers are exo/endo-mixtures with the same ratio as the silylating agent used. The isomers can be distinguished by the different chemical shifts of the methyl groups on the silyl atom in the1H NMR spectra. However, the more preferable method of analysis is 29Si NMR spectroscopy providing only two well-distinguished signals, e.g. Dimethyl-(2-norbornyl)-phenoxy silane: 1H NMR (300 MHz, CDCl3), major isomer: δ = 0.12 (2s, 6 H), 0.70 (t, 1 H), 1.10-1.5 (m, 8 H), 2.12-2.30 (m, 2 H), 6.70-6.80, 6.82-6.90, 7.09-7.20 (Phenyl, 5 H); minor isomer: δ = 0.20 [Si(CH3)2, 6 H]. 29Si NMR (99 MHz, CDCl3), major isomer: δ = +17.6; minor isomer: δ = + 19.6 ppm. Analysis by GC providing the same ratio is also possible.