‘Arc’-shaped oligophenyl derivatives with terminal
alkene moieties can be used to form macrocycles by ‘dimerization’ through
ring-closing metathesis. Hereby the introduction of templates connecting
the two building blocks favors the dimerization over oligomerization
or polymerization reactions. Attachment of the template through
imine formation allows the removal of the template simultaneous
to the reduction of the double bonds formed during ring-closing
metathesis. Unsymmetric macrocyles can be obtained either by
successive attachment of different ‘arc’-shaped molecules
to the template or by direct imine connection of two different ring
precursors. In the latter case, the imine unit cannot be cleaved
in the case of the investigated examples but ‘figure-8’-shaped
macrobicycles are obtained. The studied template-directed macrocyclization
depends on the one hand on the preorganization of the building blocks,
and on the other on their flexibility.
macrocycles - template - ring closing metathesis - imines