1,3-Dinitriles active methylene compounds

P-Dicarbonyl compounds are sometimes called active methylene compounds because they are more reactive towards base than other carbonyl compounds. Iy3-Dinitriles and a-cyano carbonyl compounds are also active methylene compounds. 

Dinitriles have been prepared by the dimerization of active methylene compounds, and by decarboxylative hydrocyanation of a-cyano-a,jS-ethyl-enecarboxylic acid esters. ... 

The Knoevenagel reaction (Scheme 6.20) involves the reaction of aromatic aldehydes with a variety of molecules CH2XY. The groups X and Y may be the same or different, but are invariably electron withdrawing, so creating an activated methylene group from which the carbanion CHXY is produced. The reaction is usually carried out in pyridine solution, with piperidine as the basic catalyst. The reactions of benzaldehyde with propane-1,3-dinitrile [malononitrile, CH2(CN)2] and diethyl propane-1,3-dioate [diethyl malonate, CH.,(CO,Et)2] are illustrative. In both cases, manipulation of the CH=CX2 group in the product allows the synthesis of other compounds. 

---