A substrate-dependent 4π/6π electrocyclization of in situ generated CF₃-heterodendralenes from 4-methyl-3-trifluoroacetyl quinolones is described. Phenyl substitution favors 4π-electrocyclization to give CF₃-substituted cyclobuta[c]quinolones bearing a CF₃-containing quaternary center, while vinyl substitution promotes 6π-electrocyclization to yield CF₃-dihydro-phenanthridones.

Herein, a substrate-divergent 4π/6π electrocyclization of hitherto unknown CF₃-heterodendralenes is disclosed, generated in situ from the 4-methyl-3-trifluoroacetyl quinolones. The reaction favors 4π-electrocyclization in the presence of a phenyl substituent, producing cyclobuta[c]quinolones featuring a challenging CF₃-all-carbon quaternary stereocenter. Conversely, vinyl substitution promotes 6π-electrocyclization to provide CF₃-dihydro-phenanthridones.