Paracyclophane-l,9-diene

Poly(l,4-naphthylenevinylenes) have been prepared by metathesis polymerization of benzobarrelenes [181,182] and the photoluminescence properties of homopolymers and block-copolymers have been studied in some detail [183]. PPV also has been prepared via ROMP of [2.2]paracyclophane-l,9-diene [184] and ROMP of a paracyclophene that contains a solubilizing leaving group [185]. The resulting polymer is converted to PPV upon acid catalysis at room temperature. ADMET of 2,5-dialkyl-l,4-divinylbenzenes using Mo or W catalysts has... 

The ROMP of [2.2]paracyclophane-l,9-diene (128) yields poly(p-phenylenevinylene) (129) as an insoluble yellow fluorescent powder. Soluble copolymers can be made by the ROMP of 128 in the presence of an excess of cyclopentene387, cycloocta-1,5-diene388 or cyclooctene389. The UV/vis absorption spectra of the copolymers with cyclooctene show separate peaks for sequences of one, two and three p-phenylene-vinylene units at 290, 345 and about 390 nm respectively, with a Bernoullian distribution. The formation of the odd members of this series must involve dissection of the two halves of the original monomer units by secondary metathesis reactions. 

Scheme 3. Bromination - dehydrobromination sequence giving l,2-dibromo[2.2]paracyclo-phane-l-ene and 1,2,9,10-tetrabromo[2.2]paracyclophane-l,9-diene [19a]...

Scheme38. Tricarbonylarenechromium complexes of dibenzo[2.2]paracyclophane-l,9-dienes [83]...

Substituted 1 2,9 10-dibenzo[2.2]paracyclophane-l,9-dienes 11 offer electronically different arene binding sites for the tricarbonylchromium moieties. Experiments with 11-H (R = H) and ll-C6H4-4-Buf (R = C6H4-4-Buf) were good for a surprise in that not only the first chromium coordinates to the central [2.2]paracyclophane, but also the second to yield the dinuclear complex 125... 

Dibenzo[2.2]paracyclophane-l,9-diene (2), a unique molecule with two parallel sets of mutually orthogonal aromatic rings, was first synthesized in 1985 by Wong et al. [18]. The reported five-step synthesis gave the strained hydrocarbon in only 0.5% yield. Later a more versatile and economic approach to dibenzoannelated [2.2]paracyclophanedienes 11 including the parent compound 2 was developed by de Meijere et al. [19]. The dibromo[2.2]paracyclo-phane-l-ene (6) and the tetrabromo[2.2]paracyclophane-l,9-diene (7) were obtained from commercially available [2.2]paracyclophane (1) in a bromination-dehydrobromination reaction sequence. With compounds 6 and 7 available in large quantities, the palladium catalyzed coupling with alkenes (Heck reaction)... 

Scheme 12.3 ROMP of 4,7,12,15-tetraoctyloxy-[2.2]paracyclophane-l,9-diene 14 to give monodis-perse, soluble poly(2,5-dioctyloxy-l,4-phenylenevinylene) 15.

Thom-Csanyi, E., Hohnk, H.D., and Pflug, K.P. (1993) Ring-opening metathesis copolymerization of cyclopentene and [2.2] paracyclophane-l,9-diene UV-Vis-spectroscopic determination of sequence-length distribution of p-pheny-lenevinylene units. Journal of Molecular Catalysis, 84,253. 

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