Template-Directed Synthesis of Symmetric as well as Unsymmetric Macro-cycles from Rigid or Flexible Building Blocks

摘要

'Arc'-shaped oligophenyl derivatives with terminal alk-ene 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.