Synthesis in the Benzoquinolizine Group. I. Synthesis of 1, 2, 3, 4, 6, 7-Hexahydro-11bH-benzo[a]quinolizines

Synthesis of 1, 2, 3, 4, 6, 7-hexahydro-11bH-benzo[a]quinolizines (IIIa and IIIb) was described. N-Phenethyl-5-bromovaleramide (IV) and 1-phenethyl-2-piperidone (VIIa) were cyclized with a mixture of phosphoryl chloride-phosphorus pentoxide and phosphoryl chloride-polyphosphoric acid, respectively, and were reduced catalytically. Thus, the hexahydro base (IIIa) was obtained. 9, 10-Methylenedioxy-1, 2, 3, 4, 6, 7-hexahydro-11bH-benzo[a]quinolizine (IIIb) was obtained in a good yield from the cyclized product of the corresponding piperidone (VIIb) by the same method.