Imines, reaction with malonic acid enolates

In their synthesis of the pyrimidine segment of the potent antitumor antibiotic bleomycin, Umezawa, Ohno and coworkers have described the reaction of highly functionalized imine (96) with malonic acid monoethyl ester to afford 3-amino ester (97 equation 16)." The low yield of (97) is largely due to elimination of the amino side chain, giving the corresponding acrylate derivative. A subsequent modification of this reaction using a boron enolate overcomes this problem and will be discussed in Section 4.1.3.2.2.ii. 

Dicarbonyl donors bearing a thioester has been applied in the Mannich reaction to A -tosyl imines. Ricci presented an enantioselective decarboxylative addition of malonic half thioester 37 to imine 38. In the Mannich-type addition, catalyst 36 deprotonates the malonic acid thioester followed by decarboxylation to generate a stabilized thioacetate enolate. This stabilized anion reacts with facial selectivity to the imine due to steric-tuning from 36 [47] (Scheme 8). 

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