Optimization of Metallocene Substrates for β-Cyclodextrin Reactions

Article abstract of DOI:10.1021/ja00347a037

The p-nitrophenyl ester of (E)-ruthenoceneacrylic acid reacts in a complex to acylate β-cyclodextrin, but with a poorer binding and rate constant than for the corresponding ferrocene derivative.The p-nitrophenyl ester of (E)-3-(carboxymethylene)-1,2-ferrocenocyclopentene is a mixture of two enantiomers.One enantiomer acylates β-cyclodextrin 5900000 times as fast in aqueous Me2SO as it hydrolyzes under the same conditions (1.5E8 times as fast as hydrolysis in pure water at the same pH); the other enantiomer is 62-fold slower.These are the largest accelerations and enantiomeric selectivities known for such reactions.Ferrocene-1,3-diacrylate esters react with β-cyclodextrin in processes in which the first and second acylation reveal important geometric effects. β-Cyclodextrin 6-tosylate is used to block unproductive binding and clarify the structural effects.