SYNTHESES OF ANTHRACENONES .1. SODIUM DITHIONITE REDUCTION OF PERI-SUBSTITUTED ANTHRACENEDIONES

The reaction of peri-substituted anthracenediones with sodium dithioni te in dimethylformamide and water has been investigated. The system se lectively reduces the carbonyl group flanked by the peri substituents of the anthracenediones to give the corresponding 4,5-disubstituted 9( 10H)-anthracenones and thus provides a route to anthracenones which ar e otherwise difficult to obtain. Many functional groups can be tolerat ed, the reaction is compatible with the presence of peri alkoxy groups and unsaturated side chains of the starting anthracenediones, and the reduction does not go beyond the anthracenone stage. However, the for mation of anthracenones depends on the nature of the peri substituents . No products were obtained from the 1,8-dimethyl-substituted anthrace nedione and the parent compound with no substituents.