Formation of a thio analog of noracronine.

Acronine was heated with tetraphosphorus decasulfide in benzene to give a mixture of products, the major component (A) being identified tentatively as an unstable product derived from four molecules of noracronine with one molecule of tetraphosphorus decasulfide. Treatment of Compound A with various solvents and heat converted it into a maroon solid (B), which was shown to be 7-thionoracronine.