Homologation Method for Preparation of Substituted Pentacenes and Naphthacenes

Multi-substituted pentacenes, such as 1,2,3,4,6,8,9,10,11,13-decasubstituted pentacenes (Type I), 1,2,3,4,6,13-hexasubstituted pentacenes (Type II), 1,2,3,4-tetrasubstituted pentacenes (Type III), and 2,3-disubstituted
pentacenes (Type IV), 1,2,3,4,6,11-hexasubstituted naphthacenes (Type V), 1,2,3,4-tetrasubstituted
naphthacenes (Type VI), and 2,3-disubstituted naphthacenes (Type VII), were prepared by a homologation
method. The homologation method involved the conversion of phthalic acid ester derivatives to two ring
extended phthalic acid ester derivatives via diynes and metallacyclopentadienes using transition metals,
such as Zr and Rh. For the formation of pentacenes of Type III and Type IV and naphthacenes of Type
VII, trimethylsilyl-substituted diynes were used for zirconocene-mediated cyclization. Elimination of the
trimethylsilyl groups after the cyclization afforded nonsubstituted position on pentacenes or naphthacenes.
Structures of 1,4,6,8,9,10,11,13-octaethyl-2,3-bis(methoxycarbonyl)pentacene (9a) and 8,9,10,11-tetraethyl-2,3-bis(methoxycarbonyl)-1,4,6,13-tetrapropylpentacene (9b) were determined by X-ray analysis. The
structure of 9a had the herringbone packing system in the crystal like nonsubstituted pentacene. However,
9b, whose substituents at 1,4,6,13-positions were changed from Et to Pr at 1,4,6,13-positions of 9a, had
the face parallel plane system in the crystal.