As part of our interest in the synthesis of heterocyclic analogues of 7,7,8,8- tetracyano-p-quinodimethane (TCNQ), in which the 7t-electrons of a TCNQ carboncarbon double bond are replaced by a lone pair of electrons on a heteroatom, we have investigated chemistry related to the synthesis of a saturated heterocyclic analogue.
Condensation of succinic anhydride with malononitrile in the presence of sodium hydride yielded the sodium salt of 4-dicyanomethylene-4-hydroxybutanoic acid. Attempts to cyclise these salts to give the corresponding dicyanomethylene lactones, potential precursors to the desired saturated analogues, by a variety of methods were unsuccessful. The corresponding sodium salt of 5-dicyanomethylene- 5-hydroxypentanoic acid was similarly synthesised from glutaric anhydride.
Further investigations into the condensation reactions of succinic anhydride and malononitrile in the presence of a variety of amines of varying basicity have been carried out and the products were isolated and characterised.