Synthèses dans le domaine des hydrocarbures cancérigènes X Le 9,10‐diméthyl‐1,2,3,4,5,6‐tribenzanthracène

Summary9,10-dimethyl-1,2,3,4,5,6-tribenzanthracene (VII) has been prepared from the corresponding quinone by the method of Sandin and Fieser. A new synthesis of 1,2,3,4,5,6-tribenzanthraquinone (VI) involving the following steps is described: condensation of phenanthrene-9,10-dicarboxylic anhydride (IV) (preparation improved) with 1-naphthyl-magnesium bromide [9-(α-naphthoyl)-10-phenanthroic acid (V)], cyclisation with H3PO4+P2O5 [1,2,3,4,5,6-tribenzanthraquinone; small yield]. The acetoxy-lactone (VIII) was isolated after treatment of the crude reaction mixture with acetic anhydride. Other cyclising agents such as C6H5COCl+H2SO4, phthalic anhydride+C6H5COCl, H3BO3+H2SO4 and ClSO3H failed to give the desired quinone. Attempts to cyclise 9-(β-naphthoyl)-10-phenanthroic acid (IX), an isomere of the above keto-acid, gave no better results. The oxydation of 1,2,3,4,5,6-tribenzanthracene with sodium bichromate in acetic acid has been shown to give a mixture of three quinones: 1,2,3,4,5,6-tribenzanthraquinone (m.p. 250–251°; yield: 52%), an ortho-quinone (only detected by isolation of the corresponding phenazine) and an ortho-para-bisquinone (m.p. 318–320°).