Geometrical isomerism and tautomerism of 3-arylidene-6-methyl-piperazine-2,5-diones

Abstract

Aromatic aldehydes condense with 3-methylpiperazine-2,5-dione in the presence of acetic anhydride to form, mainly, mono-N-acetyl derivatives of trans-3-arylidene-6-methylpiperazine-2,5-diones. In these products the acetyl group is shown to be attached to position 1 and the 4,5-amide group is found to be sterically hindered. Photolysis forms the cis-isomers. Both isomers react with base to yield the tautomeric pyrazines.