Synthesis of exo- and endocyclic enamino derivatives of 2-(3-arylprop-2-enoyl)cyclohexane-1,3-diones

Condensation of 2-acetylcyclohexane-1,3-diones with aromatic aldehydes in the presence of piperidine, pyrrolidine, hexamethyleneimine, or morpholine gave the corresponding 2-(3-arylprop-2-enoyl)cyclohexane-1,3-diones as the major products and 2-[3-aryl-1-cycloalkylaminoprop-2-en-1-ylidene]cyclohexane-1,3-diones as minor ones. Endocyclic enamino derivatives were synthesized in two steps through enol methyl ethers which reacted with amines. Endocyclic enamino derivatives of 2-(3-arylprop-2-enoyl)cyclohexane-1,3-diones containing an aryl group on the nitrogen atom readily underwent cyclization to 1,2,3,4,5,6,7,8-octahydroquinoline-4,5-dione derivatives.