Ethyl cyanoacetate, carbanion from

Reaction of carbanions with dialkynic ketones, the so-called skipped diynes, can produce pyranones through an initial Michael condensation. It should be noted however that diynones are vulnerable to attack at several sites and that mixed products can be formed. Addition of the anions derived from diethyl malonate and ethyl cyanoacetate to hepta-2,5-diyn-4-one (313 R1 = Me) gives the pyranones (314 R2 = C02Et or CN Scheme 91) (74JOC843). The former carbanion reacts similarly with the diynone (313 R1 = Bun) (68T4285). The second alkyne moiety appears to have little effect on the course of the reaction, which parallels the synthesis of pyranones from monoalkynic ketones. 

The dialdehydes from periodate oxidation of methyl 4,6-0-benzylidene-a-and -p-D-glucopyranoside reacted with appropriate Wittig reagents to give such dienes as (400) that afforded cyclized products [e.g. (401)] with nitromethane by a double Michael condensation, whereas only one of the olefinic linkages was attacked, without cyclization, with ethyl cyanoacetate and malononitrile. Details of the reactions of these dialdehydes with nitroalkanes (see Vol. 8, p. 108), ethyl cyanoacetate (see VoL 8, p. IlOX and other carbanions to give various branched-chain heptoseptanosides have also been reported. ... 

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