Synthesis of a new heterocyclic ring system 2,3,5,6,7,9,10,11‐octahydro‐l H ‐cyclopenta[9,H)]benzo[i,j] quinolizine‐1,9‐dione

Reaction of 1,2,3,4‐tetrahydroquinoline (1) with different α,β‐unsaturated acids in the presence of PPA has been investigated. With acrylic acid, 1 affords two compounds identified as 1‐keto‐benzo[ i,j ]quinolizine (III) and 2,3,5,6,7,9,10,1 1‐octahy dro‐1 H ‐cy el open ta [9,10] benzo [ i,j ]‐quinolizine‐1,9‐dione (IV). A similar reaction of 1 with a‐methyl acrylic and crotonie acids gives compounds V and VI whose structures are analogous to that of IV. These were deduced from their spectral and analytical data.