Geometrical isomerism of ethyl N-(2-pyridinyl)aminomethylenecyanoacetates

The pure cis- and trans-isomers of ethyl N-(2-pyridinyl)aminomethylenecyanoacetates were obtained and their structure and their interconvertibility is diseussed. 4H-Pyrido1,2-a]pyrimidin-4-one-3-carboxylic acids were synthesized by treatment of both cis- and trans-isomers with hydrochloric acid.