Catalysis in Aprotic Solvents. Inter- and Intramolecular Hydrogen Bonding Complexation

Article abstract of DOI:10.1021/jo00328a015

A mechanistic investigation is reported of aminolysis reactions of 2-hydroxy-5-nitro-α-toluenesulfonic acid sultone (1) in aprotic solvents.The n-butylaminolysis of 1 in acetonitrile and in toluene requires two and three molecules of amine, respectively.In the latter solvent, general bases strongly catalyze the reaction, and their catalytic constants are well correlated by the hydrogen bonding parameter pK_HB.These results are interpreted by a multistep mechanism where each intermediate can be stabilized via hydrogen bonding by general bases.The mechanistic features depend on the stability of the intermediates and on the solvent characteristics.When diamines such as polyoxyethylenediamines H2NCH2(CH2OCH2)nCH2NH2 (2, n=2; 3, n=4; 4, n=6) are used as nucleophiles for the reaction with sultone 1 in toluene, much higher reactivities are observed when compared to reactions of monoamines and alkylenediamines.This represents a novel type of intramolecular catalysis due to intramolecular hydrogen bonding complexation between oxygen atoms and the ammonium group of the reaction intermediates (Scheme III).In toluene 2-4 also display a large basicity.