Aldazines were employed in the Castagnoli-Cushman reaction of homophthalic anhydride for the first time. The reaction proved to be distinctly diastereoselective when conducted at room temperature in acetonitrile, yielding predominantly the kinetic cis -configured adduct as a racemate. Thermodynamically more stable trans -configuration could be attained either via heating the cis -configured product in DMSO or via the action of a base (imidazole) in the course of CDI-promoted esterification or amidation of the carboxylic acid function in the initial adducts. Further manipulation of the remaining N -acylhydrazone moiety in the latter led to N -alkyl- or fully unprotected N -aminolactams.