Hydroxy-ketones potassium cyanide

Mandelic Acid.—The reaction furnishes a simple and general method for obtaining hydroxy-acids from aldehydes or ketones by the aid of the cyanhydrin. The formation of the cyanhydrin may be effected in the manner described or by the action of hydrochloric acid on a mixture of the aldehyde or ketone with potassium cyanide, or, as in the case of the sugais, by the use of liquid hydrocyanic acid and a little amme-nia. 

Remarks on Sections 6 and 7.-—The method here described for the synthesis of cyanohydrins—treatment of the bisulphite compound of the aldehyde with potassium cyanide—cannot be used in all cases. Concentrated solutions of hydrocyanic acid or anhydrous hydrogen cyanide are often used. The general method for the synthesis of a-amino-acids, the nitriles of which are formed by the union of ammonium cyanide with aldehydes or ketones (Strecker), is to be contrasted with that for the synthesis of a-hydroxy acids. For additional amino-acid syntheses see Chap. VII. 2, p. 276. 

Acyloxy-l-cyanoalkanes [45, 46], which can be used as precursors for ketones [47], a-hydroxy ketones [48] and 1,4-dicarbonyl compounds [47], are prepared in one pot from the appropriate aldehyde, sodium or potassium cyanide, and the acylating agent under phase-transfer catalytic conditions [47-49]. Attempts to synthesize chiral cyanhydrins using chiral phase-transfer catalysts have been unsuccessful (see Section 12.3). 

H. Bisulphite Compounds of a-Hydroxy imino Ketones with Potassium Cyanide... 

Cyanosilylation of ketones (4,542-543 5,720). In a total synthesis of natural camptothecin (9), Corey et al used this f-butyldimethylsilyl derivative rather than trimethylsilyl cyanide (5, 720-722) to effect cyanosilylation of a ketone (1). Hydrolysis of the resulting cyano silyl ether to the required amide was not accompanied by desilylation with reversal of cyanohydrin formation. By use of carefully controlled conditions and with dicyclohexyl-18-crown-6-potassium cyanide as catalyst, they were able to convert (1) into the a-hydroxy... 

Regioselective opening of epoxide 228 with potassium cyanide in ethanol—buffer furnishes the jS-hydroxy nitrile 235. This undergoes a Reformatsky reaction [83] with tert- mXy bro-moacetate/zinc followed by a highly stereoselective ketone reduction with sodium borohy-dride/diethylmethoxyborane to provide the chiral ester 236. Subsequently, 236 is converted in four steps to optically active NK-104 (237), a highly potent HMG-CoA reductase inhibitor [84] (Scheme 55). 

It consists in the treatment of aromatic aldehydes with sodium or potassium cyanide, usually in an aqueous ethanolic solution to give a-hydroxy ketones (benzoins) (Scheme 46)7 ... 

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