The formation of chromanone-type systems via the acylation of derivatives of 2,6-dihydroxyanthracene

Abstract

Acylation of 2,6-dimethoxyanthracene with crotonoyl (but-2-enoyl) chloride leads to the formationof the corresponding 1,5-diacyl derivative. This compound, on further treatment with aluminium chloride or polyphosphoric acid undergoes intramolecular O-alkylation with fission of the methoxyl groups and formation of chromanone-type systems. Intramolecular C-alkylation which, alternatively, would have led to a perylene derivative, does not occur. A somewhat analogous sequence of reactions is observed when o-chlorobenzoic anhydride is used as acylating agent. The resulting 1,5-bischlorobenzoyl product in this case undergoes cyclisation at oxygen to yield a dixanthone derivative.