Some 4(1H)-Pyridylidene Compounds. Synthesis and Structure

The reaction of methyl 4-chloro-pyridine-2,6-dicarboxylate with a sodium compound of t-butyl cyanoacetate, ethyl cyanoacetate, or malononitrile, followed by acidification, gives the corresponding 4(1H)-pyridylidene compound, t-butyl cyano-4(1H)-(2,6-bismethoxy-carbonyl-pyridylidene)-acetate (IVa), ethyl cyano-4(1H)-2,6-bismethoxycarbonyl-pyridylidene) acetate (Va), or 4(1H)-(2,6-bismethoxy-carbonyl-pyridylidene)malononitrile (Via). The structures assigned to these compounds are based on the UV, IR and NMR spectra. In an alkaline solution, IVa, Va and Via change into the anion forms. The elimination reaction of IVa and Va is also examined.