Synthesis of ß-tropolone and fused heterocycle derivatives by acid-catalyzed and photoreactions of o-quinones with quinolines and benzimidazoles

Abstract

The condensation of 3,5-di-(tert-butyl)-1,2-benzoquinone 1 with 2-methylquinolines 2 proceeding on refluxing o-xylene solutions of the components in the presence of catalytic amounts of p-toluenesulfonic acid gives rise to previously unknown -tropolones 3. In the case of quinolines 2 containing amino or nitro groups in position 4, the reaction with quinone 8 also leads to the formation of derivatives of a novel heterocyclic system of 2-azabicyclo[3.3.0]octa-2,7-dien-4,6-dione-N-oxide 10. -Tropolones 3, under UV-irradiation, in heptane solution undergo an irreversible rearrangement leading to the formation of derivatives of 3-[(1)quinolinylidene]-1,6-di-(tert-butyl)-bicyclo[3.2.0]hept-6-ene-2,4-dione ring system 14. The reaction of o-quinone 1 with 2-methylbenzimidazole affords the derivatives of a novel condensed heterocyclic system [benzimidazo-(1,2-b)][benzimidazo-(1,2-a)-pyrrolo(3,4,5-j,i]-13,16-dihydro-16-oxoisoquinoline 17.