Studies of Alkali Fusion of Benzanthrone By-Producing Isoviolanthrone A

The relation between the yields of three isomers of violanthrone--violanthrone A (VOA), violanthrone B (VOB), and isoviolanthrone A (isoVOA)--and the condition of the alkali fusion of benzanthrone have been studied. When the method of alcoholic alkali fusion was applied to benzanthrone at low temperature, the major product was VOB. On the other hand, it was reported by Di Raddo et al. (2) that isoVOA was not obtained as a by-product under proper conditions (alkali fusion at high temperature) of synthesizing VOA. However, the result by the present authors is that 6 ～ 7 percent of the A compound is isoVOA.