Synthesis of Carboxy-Functionalized Polycyclic Arenes by Oxidative Cyclizations of 2,3-Diarylacrylates

The cyclization of esters of Perkin condensation products by oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in the presence of MeSO3H is examined as a three-step approach from arylacetic acids and aromatic aldehydes to functionalized condensed arenes. The method is limited to systems in which one or both of the two aryl moieties are more reactive than a phenyl group, such as 1-naphthyl or, especially, 3-thienyl. Alkoxycarbonyl derivatives of picene, benzo[c]chrysene, three isomeric phenanthrothiophenes, a naphthothiophene, and a benzodithiophene were obtained. The extension of this approach to multiple cyclizations and, thus, to extended partially condensed systems with multiple alkoxycarbonyl substituents appears promising with highly active precursors derived from 3-thienylacetic acid. In this case, conjugated polymers made of short ribbon fragments linked by thiophene-thiophene single bonds appear conceivable. A bifunctional chrysenodithiophene was obtained from 1,5-diformylnaphthalene, together with a highly unusual asymmetric dimer that contains a cyclohepta[de]naphthalene (pleiadiene) moiety.