A new heteropentacyclic system via coupling sterically crowded o -benzoquinone with o -phenylenediamines.

The reaction between 3,5-di( tert -butyl)- o -benzoquinone 1 and o -phenylenediamine performed under oxidative conditions that is highly sensitive to the reaction conditions (type of solvent, ratio of reactants, and duration of the reaction) gives rise to various derivatives of a new condensed 10 H -quinoxalino[3,2,1- kl ]phenoxazin-10-one heteropentacyclic system. The reaction of 1 with N -phenyl- o -phenylenediamine results in the formation of three phenazine-like compounds and, unexpectedly, a derivative of a new spiro[1,3]dioxole-2,2'-furanyl-1 H -benzo[ d ]imidazole system. The molecular structures of the prepared compounds were authenticated by NMR, mass spectra and X-ray crystallography data.