Lewis superacids derived from triflic and triflimidic acids and their use as catalysts in 1,6-diene cycloisomerisation

Abstract: We have developed a procedure for the preparation of anhydrous metallic triflates and triflimidates of general formulae M(OTf) n and M(NTf2) n based on the oxidative dissolution of metal powders in the presence of HOTf or HNTf2, respectively. The method provides salts in anhydrous form, solvates with DMSO molecules, and constitutes a good complement to a previous method developed in our group based on an electrochemical procedure. We have compared the catalytic activity of various Sn(IV) salts in the reaction of cycloisomerisation of 1,6-dienes and identified that anhydrous Sn(IV) triflimidates are more active catalysts, as compared to anhydrous Sn(IV) triflate, or their hydrated forms usually obtained by conventional methods of preparation or purchased from chemical suppliers. [Copyright &y& Elsevier]