CATALYSIS BY METAL-IONS IN REACTIONS OF CROWN-ETHER SUBSTRATES

It is the purpose of this review article to show that interaction between polyether ligands and metal ions is an effective force for catalysis. Rates of methyl transfer and acetyl transfer reactions from functionalized crown ethers to anionic nucleophiles are enhanced - even to surprisingly large extents - by group 1 and group 2 metal ions. Discussion is focused on transition state stabilization by metal ions, and on the role played by the additional binding energy rendered available by a polyether chain proximal to the reaction zone. A barium (II)-based prototype catalyst with transacylase activity is described.