Tetrahydropyrene

Hydrogenation of 4,5-dihydropyrene (2g) over 10% Pd-on-C (500 mg) in 20 ml of EtOAc at 50 psig afforded tetrahydropyrene quantitatively 17). These and many other highly regioselective results (22) contrast with the complex mixture reported earlier when more strenuous conditions were employed. 

As established, 4,5,9,10-tetrahydropyrene yields the cation and anion-radicals in the form of an equilibrium mixture of conformers (Iwaizumi and Isobe 1975 Scheme 6.25). 

In the presence of [CH(C02Et)2] , irradiation of pyrene yields 4,5,9,10-tetrahydropyrene. The reaction probably occurs by initial electron transfer to excited pyrene. ... 

The reductions of o-nitroacetanilide [65, 66] to 2-methylbenzimidazole, acylated nitronaphthylamines to naphthimidazoles [54], 2-nitrophenylthiocyanate [65] to 2-amino-benzothiazole, and 2,2 -dicarboxy-6,6 -dinitrobiphenyl to 4,9-diaza-5,10-dioxo-4,5,9,10-tetrahydropyrene [67] have been reported. 

In the case of the [2.2]- nerradical cations couple in 90% yield to give the tetrahydropyrene derivative XXVI [Eq. (16)] [146]. XXVI can be further oxidized to a pyrene [147]. [2.2]-Me a-cyclophanes with other substituents than methoxy—for example, with CH3, Br, CN, or NO2—can also be cyclized [148]. 

Consequently, by combining the synthetic procedure of Yamamoto [26] with the introduction of more extended solubilizing substituents, advantageous results were expected. Accordingly, alkyl-substituted dihydrophenanthrenes or tetrahy-dropyrenes offered themselves as starting monomers for the preparation of soluble step-ladder PPPs of this type. 2,7-Dibromo-4,9-dialkyl-4,5,9,10-tetrahydro-pyrenes (10) represent suitable starting monomers for the realization of this synthetic route. These difunctionalized tetrahydropyrene monomers were first prepared by Mullen et al. and reacted in a Yamamoto coupling [27]. 

Dibromo-4,9-diallQ l-4,5,9,10-tetrahydropyrenes Ifl represent suitable starting monomers for the realization of this syndietic route. These difunctionalized te-trahydropyrene monomers were first prepared by MtUlen et al. [18] as a precursor to 2,7-dibromo-4,9-dialkylpyrenes in a multi-step synthetic sequence. The synthesis included a Wittig olefmation starting from the bis(triphenylphosphonium) salt of 2,2 -... 

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