Thermal Elimination of Trimethylsilanol

Thermal elimination of HMDSO 7 from phosphorus compounds is discussed in Chapter 11. 

A mixture of 1 g 2,4,6-trimethoxyben2yl trimethylsilyl ether 1578 and ethylmagne-sium bromide, prepared from 1 g ethyl bromide and 0.2 g Mg in 90 mb Et20, is heated under reflux for 30 min to give, on filtration through a layer of silica gel 

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Base-catalyzed, Add-catalyzed and Thermal Eliminations of Trimethylsilanol. Peterson Reactions... 

Thermal elimination of trimethylsilanol from A,-trimethylsiloxy isoxazolidines was also documented (175, 185). Presumably, this process is accelerated by the resulting trimethylsilanol. 

In substituted methyl cholanoates (Table I) loss of water or its equivalents (acetic acid, trifluoroacetic acid, trimethylsilanol, etc.) is pronounced. In gas chromatography-mass spectrometry this process is partly thermal, partly due to electron impact when a direct probe is used, thermal elimination can be avoided. Since the mechanisms of the two types of elimination are different (26) the spectra will differ to some extent. However, in work with biological materials, the complexity of the mixtures and the small amounts of bile acids available usually make it necessary to use the former method and to accept the thermal component in the fragmentation process. When methyl esters of di- and trihydroxy bile acids and their acetates or trifluoroacetates are analyzed by gas chromatography-mass spectrometry, a molecular ion is usually not seen. This is partly due to the high temperatures used. Trimethylsilyl ethers usually give a molecular ion peak but it may be quite small. 

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