Intermolecular sequential [4 + 2]-cycloaddition-aromatization reaction of aryl-substituted allenes with DMAD affording phenanthrene and naphthalene derivatives

An efficient entry to phenanthrene and naphthalene derivatives through intermolecular sequential [4 + 2]-cycloaddition-aromatization reactions of aryl-substituted allenes with DMAD in the absence of any catalyst was discovered. In this reaction the aromatic ring and the adjacent carbon-carbon double bond of the allene unit acted as the 1,3-diene.