Reactions of ketonic Mannich bases with malononitrile and malononitrile dimer

The reaction of malononitrile with the tertiary Mannich base hydrochloride derived from acetophenone and some related compounds 1, 3, 5 and 7, in piperidine at 50°C afforded the pyrido[1,2-a]pyrimidine derivatives 2, tetrahydronaphthalene derivative 4 substituted quinolines 6 and benzopyran derivatives 8. While the condensation of malononitrile dimer with acetophenone, cyclohexanone and/or α-tetralone Mannich bases hydrochloride 1, 3 and 9 gave the pyridine, isoquinoline and benzo[f]isoquinoline derivatives 10-12 in moderate to good yield.