Azepino[1,2-a]indole Synthesis from a 1,2,3,4-tetrahydro-9(10H)-acridinone and sodium dichloroisocyanurate or singlet oxygen

Sodium dichloroisocyanurate (4) acts on 7-methyl-1,2,3,4-tetrahydro-9(10H)-acridinone (1) to give principally either cis-1,2-diol 2 or azepino[1,2-a]indole 3, by suitable choice of reactant proportions. 2,3,6-Trimethyl-4-(1H)-quinolinone (6) yields a novel, methylene-bridged, oxygenated dimer 9, while with excess 4 the chief product is the 1,2-dihydro-3H-indol-3-one 7. 6-Methyl-2-phenyl-4(1H)-quinolinone (12) initially gives the 3-chloro derivative 14, which then reacts further with 4, yielding chlorine-free 6-methyl-2-phenyl-4H-3,1-benzoxazin-4-one (16). The sensitized photooxidation of acridinone 1 furnishes azepinoindole 3 en route to dicarboxylic acid 5; upon similar treatment, quinolinone 6 provides the analogous indolone 7. Reaction pathways to account for the results are presented. N-Halo imide 4 offers advantages over the more conventional NaOCl in synthesis as illustrated also with a "one-pot" Hofmann degradation of 4-chlorobenzamide.