Microwave-assisted multicomponent reactions: rapid and regioselective formation of new extended angular fused aza-heterocycles.

A new multicomponent domino reaction for rapid and regioselective synthesis of highly functionalized benzo[h]naphtho[2,3-a]acridine-15,16(5H,14H)-diones has been established. The reaction can be conducted by using readily available and inexpensive substrates under microwave irradiation. The procedures are facile, avoiding timeconsuming and costly syntheses, tedious work-up and purifications of precursors as well as protection/deprotection of functional groups. This method is much more efficient due to short reaction times and easy work up. The resulting naphthoacridines have been readily converted into benzoquinoxaline-fused benzoquinoline analogues by treating with benzene-1,2-diamine under microwave irradiation. The structural assignment has been ambiguously confirmed by X-ray analysis. A new mechanism has been proposed for this new multicomponent domino process.