HETEROGENEOUS CATALYSIS OF ASYMMETRIC DIELS-ALDER REACTIONS

Zn(II)-exchanged K10-montmorillonites, activated by several methods, a re used as catalysts in the asymmetric Diels-Alder reactions of acryla tes of (-)-menthol and (-)-8-phenylmenthol with cyclopentadiene. Calci ned clays show a higher catalytic activity and lead to better percenta ges of diastereomeric excess in the case of acrylate of (-)-menthol. F urthermore, calcined clays are easily recovered with no loss of cataly tic properties. In the case of the acrylate of (-)-8-phenylmenthol, th e percentages of diastereomeric excess are lower than expected, due to the significant contribution of the non-catalysed reaction.