Synthesis of 1,2,5,6,10a,10b-hexahydroindeno[7,1,2-hij]quinolizine-3,10-dione: a new heterocyclic ring system
Abstract
Diethyl 1-(3,4-dihydroisoquinol-1-yl)glutarate is cyclised reductively to give ethyl 4-oxo-1,3,4,6,7,11b-hexahydro-2H-benz[a]quinolizine-1-carboxylate: this ester and the corresponding acid are further cyclised by polyphosphoric acid forming 1,2,5,6,10a,10b-hexahydroindeno[7,1,2-hij]quinolizine-3,10-dione.