PURPOSE: To profitably obtain dialkyl 2,3-pyridinedicarboxylates useful as intermediates of herbicides from easily available starting materials by reacting a specified α,β-unsatd. oxime with a specified aminobutenedioate in the presence of an acid at elevated temp.

CONSTITUTION: An α,β-unsatd. oxime of formula I (Y and Z are each H or 1-4C alkyl optionally substd. by 1-3 halogen atoms or 1-4C alkoxy) is reacted with an aminobutenedioate of formula II (R1 and R2 are each phenyl or 1-4C alkyl optionally substd. by phenyl; and R3 and R4 are each H, 1-6C alkyl or the like) in the presence of an acid, preferably hydrochloric acid and of a solvent if necessary at an elevated temp., preferably the reflux temp. to obtain the objective dialkyl 2,3-pyridinedicarboxylates of formula III. Diethyl 5-ethyl-2,3- pyridinedicarboxylate as one of the compds. of the formula III is obtd. from 2-ethylacrolein oxime and diethyl 2-aminobutenedioate.