Product transformation, cyclophanes

Twofold inter- and intramolecular PKRs have found interesting applications in synthesis of ansa-zirconocenes. An early example illustrated the use of this approach for the synthesis of cyclopentadiene anellated[2,2]para-cyclophanes 157-158. The reaction of several paracyclophanedienes (155) with alkynes gave the corresponding twofold cycloaddition products 156, which were transformed into cyclopentadienyl anions orthogonally attached to the bridges of the paracyclophane (Scheme 46) [158]. 

The solid [2.2]-p-cyclophane was sublimated at 383 K, and the vapors were passed through a pyrolitic quartz tube at 873 K. This compound converts into PX without formation of detectable side products under these conditions [29, 30]. As stated in reference 22, solid PX most probably contains polymer chain precursors in the form of monomer stacks transforming into polymer chains as a result of the rather small rotational displacement of molecules without their translation movement. The assumed pattern of the solid-state PX polymerization is presented in Figure 2.1. 

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