Anthraquinone and anthrone series

Summary

The orientation of the nitro groups in dinitrodibenzanthrone produced by nitration of dibenzanthrone has not been established so far. The suggestion of Simonsenet al. ⁵ that the nitro groups are in the 3∶12-positions has been disproved by the unambiguous synthesis of 3∶12-diaminodibenzanthrone (IV), which was found to be different from the diamino derivative obtained by the reduction of the above dinitrodibenzanthrone. The diaminodibenzanthrone (IV) was synthesized from 3∶3′-dibenzanthronyl (V) by nitration to 9∶9′-dinitro-3∶3′-dibenzanthronyl (VI) and conversion of the latter in one step to (IV). The 9∶9′-orientation of the nitro groups in (VI) was shown by its oxidation to 6-nitroanthraquinone-1-carboxylic acid.

Derivatives of 3∶3′-dibenzanthronyl of definite orientation are useful as intermediates for the corresponding dibenzanthrone derivatives. Thus the dinitrodibenzanthronyl (VI) has been converted to 3∶12-dichloro- and 3∶12-diaminodibenzanthrone.