| Abstract
| - A modular synthetic strategy for the constructionof cofacial porphyrin architectures bearing hydrogen-bondsynthons on a xanthene platform is presented. The convergent approach is based on a xanthene aldehyde-ester building block that is easily obtainable on a multigram scale withminimal purification. Treatment of this xanthene derivativewith a variety of aryl aldehydes and pyrrole under standardLindsey conditions affords a family of meso-substitutedporphyrins bearing a single functionalized xanthene spacer.Direct modification of the hydrogen-bond synthon aftermacrocyclization proceeds smoothly to furnish porphyrinsystems with a variety of cofacial functionalities (e.g.,carboxylic acid, ester, amide). Porphyrins bearing two trans-functionalized xanthene spacers are prepared by the MacDonald [2 + 2] condensation of the xanthene aldehyde-esterwith readily available 5-aryl-substituted dipyrromethanessuch as 5-mesityldipyrromethane to afford the pure α,α- andα,β-porphyrin atropisomers after chromatographic separation. The versatility of this synthetic method offers intriguing opportunities for the use of these and related templatesfor the study of proton-coupled activation of small molecules.
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