Effects of cyclodextrin on hydrolysis and the Smiles rearrangement of salicylic acid esters

The effect of -cyclodextrin (-CD) on aqueous hydrolysis of methyl,p-, andm-nitrophenyl salicylates as well as on the Smiles rearrangement ofp-nitrophenyl salicylate was studied. No effect of -CD on the pH-independent rate constant of aqueous hydrolysis of methyl ester was observed, while -CD accelerated aqueous hydrolysis of nitrophenyl esters byca. 10 times. The inclusion of these esters into the cavity of -CD is accompanied by a change in the mechanism of hydrolysis: free ester in the deprotonated form undergoes hydrolysis through the mechanism of intramolecular general base catalysis, while the ester bound to cyclodextrin is hydrolyzed due to the nucleophilic attack of the deprotonated hydroxyl group of -CD at a neutral substrate molecule. The effects of cyclodextrin on the rate constant of borate-catalyzed hydrolysis were interpreted by assuming that the substrate bound to -CD undergoes borate-assisted attack at the deprotonated cyclodextrin hydroxyl group. The Smiles rearrangement, which is an intramolecular nucleophilic substitution reaction, is accelerated in the presence of -CD.Translated fromlzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2658–2665, November, 1996.