Silyl cyanide

Pyridine A-oxides have been utilized as asymmetric catalysts in the allylation of aldehydes <06JOC1458> and in the Strecker reaction <06T4071>. In the latter, the chiral A-oxides played a key role in the initial activation of the Si-C bond by coordinating an O atom to the Si atom of silyl cyanide and stabilizing the three-membered complex proposed by the... 

The Strecker reaction of silyl cyanide (H3SiCN) with benzaldehyde A-methylimine (PhCH=NMe), catalysed by an axially chiral 2,2 -bipyridine A,A -dioxide has been explored computationally as a model for the corresponding reaction using TMSCN, PhCH=NCH2Ph, and a biquinoline dioxide.70 The non-catalysed reaction is found to be concerted (via a five-membered ring TS), whereas the catalysis is stepwise, via a hexacoordinate hypervalent silicate. 

Simultaneous treatment of a carbonyl compound with a Lewis acid and a tertiary amine or another weak base ( soft enolization ) can sometimes be used to generate enolates of sensitive substrates which would have decomposed under strongly basic reaction conditions [434]. Boron enolates, which readily react with aldehydes at low temperatures, can also be prepared in situ from sensitive, base-labile ketones or carboxylic acid derivatives [293, 295, 299]. Unwanted decomposition of a carbanion may also be prevented by generating it in the presence of an electrophile which will not react with the base (e.g. silyl halides or silyl cyanides [435]). 

The structure of silyl cyanides was a matter of dispute for many years. Emeleus, Maddock and Reid (1941) prepared silyl cyanide by the reaction of SiH3I with solid AgCN. The normal cyanide structure was written for this product without comment. However, on the basis of analogy with carbon chemistry, MacDiarmid (1956) suggested that the compound should be formulated as an isocyanide, H3SiNC. The problem Was finally resolved by careful infrared and microwave spectral studies which showed that the normal cyanide, H3SiCN, is correct (Linton and Nixon, 1958 a Mutter and Bracken, 1960 Sheridan and Turner, 1960). 

Sheridan, J. and A. C. Turner Microwave Spectrum of Silyl Cyanide. Proc. Chem. Soc. 21 (1960). 

Cyanosllylations have generally been accomplished by addition of a tri-alkyl silyl cyanide to the corresponding aldehyde or ketone. J Although this method is straightforward and proceeds in good to excellent yield, use of pre-... 

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