Lithium pentacene

Another method for e preparation of aryl w-dimethoxyethyl sulfides was described by Pandya and Tilak. The procedure consists in allowing aryl lithium derivatives to react with 2,2,2, 2 -tetramethoxy-diethyl disulfide. Subsequent cyclization of the sulfides by polyphos-phoric acid yields 2-35% of condensed thiophenes and thiopyrans. By this method, thienothiophene 1 was prepared from 2-thienyllithium [Eq. (12)] and the previously unknown dithieno[2,3-6 3, 2 -i/]thiophene (5) was obtained from thienyl-2,5-dilithium. The possibility of synthesizing a heterocyclic analog (25) of pentacene from dithieno[2,3-6 3 2 -[Pg.130]

Pentacene diquinone (4) was reduced electrochemically with one Faraday/mole, and the semiquinone salt was precipitated. Four-point-probe measurements were made on pressed pellets at room temperature. The lithium salt and tetramethylammonium salt had a = 1 [4] and a = 0.02 S cm-i, respectively. Such high conductivities are not measured on mono-semiquinones. For example, naphthacene quinone has a < S cm-i. 

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