HETEROGENEOUS CATALYSIS OF ASYMMETRIC DIELS-ALDER REACTIONS

Zn(II)-exchanged K10-montmorillonites, activated by several methods, are used as catalysts in the asymmetric Diels-Alder reactions of acrylates of (-)-menthol and (-)-8-phenylmenthol with cyclopentadiene. Calcined clays show a higher catalytic activity and lead to better percentages of diastereomeric excess in the case of acrylate of (-)-menthol. Furthermore, calcined clays are easily recovered with no loss of catalytic properties. In the case of the acrylate of (-)-8-phenylmenthol, the percentages of diastereomeric excess are lower than expected, due to the significant contribution of the non-catalysed reaction.