7677-24-9

Preparation

Trimethylsilyl cyanide, (CH3)3 Si-CN, is obtained by reacting trimethylsilyl chloride with an approximately equimolar amount of an alkali metal cyanide in the absence of water and in the presence of catalytic, sub-stoichiometric amounts of both an alkali metal iodide and N-methylpyrrolidone, at a temperature of from 15°-25° C. Trimethylsilyl cyanide is very toxic. All reactions in this sequence should be carried out in a hood. Preparation of trimethylsilyl cyanide TRIMETHYLSILYL CYANIDE: CYANOSILATION OF p-BENZOQUINONE

Reactions

Trimethylsilyl cyanide is a useful silicon reagent which reacts readily with aldehydes and ketones in the presence of catalytic amounts of Lewis acids or of cyanide ion, to give the trimethylsilyl ethers of the corresponding cyanohydrins (Evans,Carroll and Truesdale,1974).Even normally unreactive ketones react readily with trimethylsilyl cyanide due to the formation of the strong Si-O bond which displaces the equilibrium in favour of the derivative.The reaction provides a valuable alternative to the base-catalysed addition of hydrogen cyanide to carbonyl compounds which often gives only poor yields.Tetralone，for example,is reported not to form a cyanohydrin, but it gives a trimethylsilyl derivative in excellent yield.The silylated cyanohydrins can be hydrolysed to a-hydroxy acids(Corey, Crouse and Anderson,1975) and on reduction with lithium aluminium hydride they afford the corresponding 3-amino alcohols in excellent yield.This sequence provides a better route to these valuable intermediates (they are used in the ring expansion of cyclo- alkanones)than the classical methods through reaction of hydrogen cyanide or nitromethane with the carbonyl compound.The derivatives from aromatic aldehydes are excellent acyl anion equivalents and have been used in 'umpolung' conversion of aldehydes into ketones and acyloins by reaction of the derived anions with alkyl halides and aldehydes or ketones (Deuchert et al，1979;Hnig and Wehner,1979).

Purification Methods

The material should have only one sharp signal in the 1H NMR (in CCl4 with CHCl3 as internal standard) : 0.4ppm and IR with max at 2210cm
1 [McBride & Beachall J Am Chem Soc 74 5247 1952, Prober J Am Chem Soc 77 3224 1955]; otherwise purify it by fractionating through an 18 x 1/4inch column. [Evers et al. J Am Chem Soc 81 4493 1959.] It has also been carefully distilled using a 60cm vacuum jacketed column. If the volume of sample is small, the cyanide can be chased (in the distillation) with xylene that had been previously distilled over P2O5. It is HIGHLY TOXIC and FLAMMABLE. [Evans et al. J Org Chem 39 914 1974, Beilstein 4 IV 3893.]

Physical properties

Trimethylsilane cyanide is a colorless volatile liquid with almond odor, soluble in most organic solvents, such as dichloromethane, chloroform, etc.; it reacts violently with protic solvents such as water. This compound is used in organic synthesis as a replacement reagent for highly toxic HCN to introduce cyano groups into molecules.