Supramolecular Cyclophane Chemistry

Abstract

This account illustrates the rich supramolecular chemistry of cyclophanes with preorganized apolar cavity binding sites. These artificial receptors, which are constructed via relatively short synthetic routes, form structurally well defined inclusion complexes with a diversity of organic substrates. Among the molecules that form stable liquid phase complexes are flat arenes, paracyclophanes, steroids, and nucleosides. Dispersion and aromatic-aromatic interactions in addition to solvophobic forces provide the major driving forces for the binding of neutral solutes. Comprehensive studies have provided unique insight on the individual molecular level into solvent effects on tight apolar complexation. For enantioselective binding in liquid phase, 1,1’-binaphthyl units and unnatural alkaloids are incorporated as chiral spacers into optically active cyclophanes. The functionalization of the receptors with coenzyme derivatives yields efficient supramolecular catalysts. Porphyrin-cyclophanes show cytochrome P-450 monooxygenase activity and epoxidize reactive aromatic hydrocarbons in protic solvents. In a synthetically useful process, aromatic methyl esters are prepared efficiently and selectively over aliphatic methyl esters by electrochemical oxidation of aldehydes mediated by biscoenzyme - flavin and thiazolium-cyclophane - catalysis at an extraordinarily low potential in methanol.