Synthesis of Crown Ethers That Geometrically Orient Cations Relative to a Naphthalene ? System. A Look at the Equilibration of Enantiomeric Conformations by "Rope-Skipping" Crown Ethers

Article abstract of DOI:10.1021/jo01297a031

A number of new naphthalene crown ethers were synthesized in moderate yield from the appropriate bis(halomethyl)naphthalenes and polyethylene glycols.The following crown ethers were synthesized: 2,3-naphtho-14-crown-4 (15percent), 2,3-naphtho-17-crown-5 (19percent), 2,3-naphtho-20-crown-6 (36percent), 1,8-naphtho-15-crown-4 (20percent), 1,8-naphtho-18-crown-5 (7percent), 1,8-naphtho-21-crown-6 (38percent), 1,2-naphtho-20-crown-6 (4percent), 1,5-naphtho-22-crown-6 (14percent), 1,5-naphtho-19-crown-5 (11percent), 1,4-naphtho-22-crown-6 (9percent), 1,3-naphtho-21-crown-6 (16percent).These crown compounds form a series in which complexed cations perturb the naphthalene ? system from different directions.Experimental evidence concerning the ease of equilibration of enantiomeric conformations by "rope-skipping" crown ethers is also reported.The equilibration of 1,5-naphtho-22-crown-6 enantiomeric conformations has about a 6.3-kcal energy of activation, while the corresponding barrier for 1,5-naphtho-19-crown-5 is greater than 21 kcal.