The Mannich bases of naphthalene series in the synthesis of 14H-dibenzo[a,j]xanthenes

Abstract

14H-Dibenzo[a,j]xanthenes attracted attention of researchers due to their antitumor activity [1–3]. Numerous examples of the synthesis of such compounds are described mainly by pseudo three-component condensation of 2-naphthol and aromatic aldehydes in the presence of various catalysts [4–7]. However, the conversion of Mannich bases, 2-naphthol derivatives, into 14H-dibenzo[a,j]xanthenes, except for one example involving 1-[(dimethylamino)(phenyl)methyl]-2-naphthol [8], was not performed. We found that Mannich bases of naphthalene series Ia–Ie transformed into dibenzoxanthenes IIa–IIe in yields of 36–50% under reflux in acetic acid (Scheme 1).