Reaction of Anthraquinones with Enaminones
Stoodley converted the anthraquinone to the oxirane (3)1 in two steps (scheme 1) to be used in anthracyclinone synthesis (as in the chemistry section of this website). The anthraquinone (2) reacts with a variety of enaminones, for example (6) to form naphtho[2,3-g]indoles (7)2, which were tested for anti-cancer activity in a similar fashion to the anthracyclines. Schenck, amongst other studies, also found that the indole (7) rearranged in methanolic hydrogen chloride to afford the dibenzo[c,f]azonine-8-carboxylate of type (8), again tested for activity (scheme 2).
In a similar fashion, Schenck2 discovered that the chloro-anthraquinone3 (5) also under went the modified Nenitzescu reaction with an enaminone (9) to afford the naphtho[2,3]indole of type (10) (scheme 3). These new compounds were confirmed by full spectroscopic and X-Ray analysis and some were cytotoxically active against carcinoma cell lines.
1. M. Chandler and R. J. Stoodley, J. Chem. Soc., Perkin Trans 1, 1980, 1007.
2. L. W. Schenck, "Darstellung anthracyclinanaloger Strukturen mit Hilfe einer modifizieren Nenitzescu-Reaktion", Ph.D. Thesis, Heinrich-Heine University of Düsseldorf, 2003.
3. P. Cano, F. Fariña, M. Dolores, J. Chem. Soc., Perkin Trans. 1, 1986, 1925.