Cyclodehydration of non-aromatic diols on Al<SUP>III</SUP>-montmorillonite clay: reactivity and mechanism

AlIII-Montmorillonite-catalysed reactions of non-aromatic diols and butane-1,4-dithiol into the corresponding heterocyclic compounds are described. Experiments with S-(+)-pentane-1,4-diol indicate a mechanism involving competitive protonation of the primary and secondary hydroxy groups, followed by SN2 displacement of water to form the cyclic product. A comparison of the relative catalytic efficiencies of AlIII-montmorillonite and the corresponding alumina pillared clay suggests that the performance of the former is superior in the above acid-catalysed reactions