Scope and limitations of montmorillonite K 10 catalysed opening of epoxide rings by amines

Abstract

Montmorillonite K 10 efficiently catalyses the opening of epoxide rings by amines in high yields with excellent regio- and diastereo-selectivities under solvent-free conditions at room temperature affording an improved process for synthesis of 2-amino alcohols. Reaction of cyclohexene oxide with aryl/alkyl amines leads to the formation of trans-2-aryl/alkylaminocyclohexanols. For unsymmetrical epoxides, the regioselectivity is controlled by the electronic and steric factors associated with the epoxide and the amine. Selective nucleophilic attack at the benzylic carbon of styrene oxide takes place with aromatic amines, whereas, aliphatic amines exhibit preferential nucleophilic attack at the terminal carbon. Aniline reacts selectively at the less hindered carbon of other unsymmetrical epoxides. The difference in the internal strain energy of the epoxide ring in cycloalkene oxides and alkene oxides led to selective nucleophilic opening of cyclohexene oxide by aniline in the presence of styrene oxide. Due to the chelation effect, selective activation of the epoxide ring in 3-phenoxy propylene oxide takes place in the presence of styrene oxide leading to preferential cleavage of the epoxide ring in 3-phenoxy propylene oxide by aniline.