Insight into and Computational Studies of the Selective Synthesis of 6H-Dibenzo[b,h]xanthenes

Starting from 2-hydroxy-1,4-naphthoquinone (lawsone), we synthesized eight new 6H-dibenzo[b,h]xanthene derivatives selectively under solvent-free conditions. Spectroscopic investigations confirmed that only the isomer 6H-dibenzo[b,h]xanthene was obtained in all eight cases. Computational studies provide a rationalization for the selective appearance of these isomers having as an intermediate an addition product.