Synthesis of quinolines, 2-quinolones, phenanthridines, and 6(5H)-phenanthridinones via palladium[0]-mediated Ullmann cross-coupling of 1-bromo-2-nitroarenes with β-halo-enals, -enones, or -esters

Palladium[0]-mediated Ullmann cross-coupling of 1-bromo-2-nitrobenzene (1 R = H) and its derivatives with a range of β-halo-enals, -enones, or -esters readily affords the corresponding β-aryl derivatives, which are converted into the corresponding quinolines, 2-quinolones, phenanthridines, or 6(5H)-phenanthridinones on reaction with dihydrogen in the presence of Pd on C or with TiCl₃ in aqueous acetone.