EXPERIMENTS DIRECTED TOWARDS THE SYNTHESIS OF ANTHRACYCLINONES .22. NOVEL CYCLOPROPANATION REACTIONS

Iodine/potassium carbonate induced cyclization of hydroxyanthraquinone s with ortho-allyl side chains gives iodomethyldihydrofuran anthraquin ones which undergo a novel cyclopropanation reaction on treatment with methanolic potassium hydroxide, e.g. (9) gives (12) in 77% yield, and (10) gives (13) in 62% yield. The scope of the reaction is explored a nd a number of by-products are identified and, where possible, their f ormation is rationalized.