ABSTRACT
This chapter deals with the nonaromatic unsaturated crown ethers carrying carbon-carbon multiple bond; for the syntheses and/or cation binding of the azo and imino crown ethers, sees the review by Shinkai and Manabe and the paper by Luk'yanenko et al respectively. The syntheses and cation-binding properties of the areno crown ethers have been the subject of extensive investigations from the very beginning of crown ether chemistry by C. J. Pedersen. The multiple bond in a crown ring is expected to alter the cation-binding properties substantially through the electronic and structural deviations from the common saturated 3m-crown-m ethers. The introduction of a multiple bond to a crown ether enables direct and/or sensitized photochemical excitation. The singlet oxygenation of stilbeno crown ethers provides direct access to novel dioxetano crown ethers. The cation binding by the unsaturated crown ethers should be further surveyed quantitatively to reveal the structural and electronic effects of the multiple bond on cation binding, including the possible soft pi-interaction.
