Glutarates 2,3-disubstituted

Closely related to enolate additions to enones is the diastereoselective 1,4-addition of lithium enolates of esters, thioesters and amides to a,/ -unsaturated esters. These reactions provide syn-or ar /-2,3-disubstituted glutarates (pentanedioates). 

The addition of ester enolates to oi.P-unsaturated esters occurs with identical diastereoselectivity as shown for a,(3-enones this is exemplified by the diastereoselective synthesis of erythro- and threo-2,3-disubstituted glutarate esters (178 and 179). 146 -c Similarly, Yamaguchi reports a general synthesis of /ra/tJ-2-alkoxycarbonyl-l-cycloalkanepropionates (181-184) from w-halo-a,(3-unsaturated esters (180),... 

Ethyl cyanoacetate condenses with ketones and ammonia in absolute ethanol at 0-5° to give 44-73% yields of cyclic dicyanoimides. Endocyclic ketones may be used, giving imides in which the two radicals are p>art of an alicyclic ring. The imides are hydrolyzed and decarboxylated in almost theoretical yields to yS,/S-disubstituted glutaric acids. A similar reaction takes place between aldehydes or ketones and cyanoacetamide, NCCHjCONHj, in the presence of piperidine or potassium hydroxide. When aldehydes are used, the condensation products are dicyanoamides, RCH[CH(CN)CONHj]j, rather than cyclic imides. 

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