Efficient syntheses of interlocked molecules based on hydrogen-bonding: Recent progress in syntheses of rotaxanes and catenanes

Due to the marked progress in control of intermolecular interactions that assemble component molecules, directed synthesis of interlocked molecules such as rotaxanes and catenanes has recently developed greatly. This review summarizes the efficient synthesis of interlocked compounds based on hydrogen-bonding interaction. Various synthetic methods including threading followed by end-capping, clipping, slipping, entering, and polyslipping are discussed. Synthesis under thermodynamic control is also discussed. Various amide-based catenanes and rotaxanes have been synthesized using the template effect based on amide-amide hydrogen-bonding or anion-recognition by macrolactam. The strong hydrogen-bonding between cucurbituril and ammonium salts allowed to prepare various structures of catenanes, rotaxanes, and polyrotaxanes. Further, secondary ammonium salts can be captured into the rings of crown ethers consisting at least 24 ring member to give pseudorotaxanes. A wide variety of end-capping techniques have been developed to give crown ether-based rotaxanes. Control of intramolecular hydrogen-bonding interaction in the interlocked compounds are briefly discussed.