Synthesis and properties of 4-ethoxyfluoranthenopyrylium salts and fluoranthenopyrones

The mutual effect of the parts of the fluoranthene molecule was studied in the case of the pyrylation reactions of isomeric o-hydroxy ketones of fluoranthene [11-hydroxy-12-acetyl-(phenylene part) (I) and 4-hydroxy-3-acetyl-fluoranthene (naphthalene part) (I′)]. Pyrylium salts were obtained, and the yields were higher from I than from I′; this indicates conjugation of the π-electron systems of the parts of the fluoranthene molecule. Fluorantheneopyrones and their derivatives were also obtained. It is shown that the mutual effect of the parts of the fluoranthene molecules does not have a substantial influence on the results of the reactions that take place in the pyrone ring. The structures of the compounds obtained were proved by alternative synthesis.