Aldazines in the Castagnoli–Cushman Reaction

Abstract

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.