Synthesis and Reactions of Some New Benzo[a]phenothiazine-3,4-dione Derivatives

The reaction of 2,3-dihydro-2,3-epoxy-1,4-naphthoquinone (4) with substituted anilines furnished the corresponding benzo[fused]heterocyclic derivatives 5, 6, 6a, 6b, 7, 8. Furthermore, treatment of benzo[a]phenothiazine derivative 7 with halo compounds, namely, ethyl bromoacetate, phenacyl bromide, dibromoethane, or chloroacetone afforded ether derivatives 11, 12, 13, 14, respectively. Moreover, the reaction of 11 with o-substituted aniline gave the corresponding benzo[a]phenothiazin-5-one derivatives 15, 16, 17 and benzo[d][1,3]oxazin-4-one18, respectively. Finally, the chromenone derivative 19 was synthesized via the reaction of ester derivative 11 with salicyaldhyde in refluxing pyridine. The newly synthesized compounds were characterized by spectroscopic measurements (IR, ¹H NMR, ¹³C NMR, and mass spectra).