Solvent-free Huisgen cyclization using heterogeneous copper catalysts supported on chelate resins

Copper catalysts supported on chelate resins bearing iminodiacetate moieties (DIAION CR11) or polyamine moieties (DIAION CR20) as chelating functional groups (12% Cu/CR11 and 7% Cu/CR20, respectively) were developed. 12% Cu/CR11 effectively catalyzed the Huisgen cycloaddition of mono-substituted alkynes to azides in the presence of triethylamine under totally solvent-free conditions to afford the corresponding 1,4-disubstituted 1,2,3-triazoles in excellent yields and in a completely regioselective manner. Furthermore, the Huisgen cycloaddition was found to effectively proceed without addition of triethylamine by the use of 7% Pd/CR20 as a catalyst.