A mechanistic investigation is reported of aminolysis reactions of 2-hydroxy-5-nitro-alpha-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 pKm. 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 H 2NCH2(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 111). In toluene 2-4 also display a large basicity.
CATALYSIS IN APROTIC-SOLVENTS - INTERMOLECULAR AND INTRAMOLECULAR HYDROGEN-BONDING COMPLEXATION
LEONI, PIERO
1981-01-01
Abstract
A mechanistic investigation is reported of aminolysis reactions of 2-hydroxy-5-nitro-alpha-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 pKm. 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 H 2NCH2(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 111). In toluene 2-4 also display a large basicity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
