The Use of Silylation in Organic Syntheses

The term silylation is used to denote the introduction of a triorganosilyl moiety, especially the trimethylsilyl species, into organic compounds. ‐ Silylated amino acids and sugars are particularly suitable for the syntheses of peptides and saccharides, respectively, since the silyl group can be cleaved off readily under mild conditions. Many diamines undergo ring closure, e.g. with phosgene, only after silylation. ‐ O‐silylated lactim ethers (i.e. cyclic imino ethers) are converted into N‐alkyl derivatives by alkyl halides. Compounds with a strongly polarized SiC bond may be used for chain extension. Silyl esters of halogeno fatty acids yield lactones with silver cyanate. ‐ Trimethylsilyl azide is thermally very stable and behaves like organic azides. It reacts with acetylenic compounds, trialkylphosphines, and triarylphosphines to yield silylated triazole derivatives, trialkylphosphines N‐silylimines, and triarylphosphines to yield silylated triazole dervatives, trialkylphosphine N‐silylimines, and triarylphosphine N‐silylimines, respectively, from which the silyl groups can be removed under mild conditions.