Acyl anion equivalents metallated cyanohydrins

In 1971 Stork and Maldonado214 showed that anions derived from 0-pro tec ted cyanohydrins of aldehydes could be efficiently metallated and the resultant anions could serve as synthetically useful acyl anion equivalents. Other develop-... 

Before 1960, only sodamide and potassium amide were used for the a-metallation of nitriles ( CH—C=N) and successful couplings with electrophiles were restricted to alkylations [la]. The extension of the number of base-solvent systems allowed a clean a-metallation of a variety of nitriles and the subsequent successful reaction with other nucleophiles [lb]. The use of a-metallated dialkyl-aminonitriles R2NCH(R )C=N and protected cyanohydrins R CH(C=N)OR (R = SiMe3 or CH(CH3)OEt) as acyl-anion equivalents in organic synthesis has been reviewed by Albright [2]. 

Heteroatom-stabilized Carbanions. Heteroatom-stabilized and allylic carbanions serve as homoenolate anions and acyl anion equivalents, e.g. a-anions of protected cyanohydrins of aldehydes and Q ,/3-unsaturated aldehydes are intermediates in general syntheses of ketones and Q ,/3-unsaturated ketones (eq 36). Allylic anions of cyanohydrin ethers may be a-alkylated (eq 37) or, if warmed to —25°C, may undergo 1,3-silyl migration to cyanoenolates which may be trapped with TMSCl. Metalated Q -aminonitriles of aldehydes are used for the synthesis of ketones and enamines (eq 38). Similarly, allylic anions from 2-morpholino-3-alkenenitriles undergo predominantly a-C-alkyl-ation to give, after hydrolysis, a,/3-unsaturated ketones (eq 39). ... 

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