Nontemplated versus templated synthesis of a 56-membered macrocycle

The amine-Substituted quinquephenylene 1 was prepared in a Suzuki coupling approach and by reaction with terephthalic dialdehyde (7) it was transformed into the phenyl-connected diimine 8. Ring-closing metathesis with the Grubbs I or II catalyst led to the corresponding macrocycle 9. Hydrogenation resulted in the reduction of the double bonds as well as the removal of the template to yield the 56-membered macrocycle 6 in an overall yield of 43% (from 1). Direct metathesis reaction of I followed by hydrogenation afforded 6 in only 21% yield.