β-Cyclodextrin-mediated highly efficient [2+3] cycloaddition reactions for the synthesis of 5-substituted 1H-tetrazoles

A beta-cyclodextrin-promoted [2+3] cycloaddition reaction between nitriles and sodium azide in the presence of ammonium chloride in DMF at 120 degrees C is reported, affording various 5-substituted 1H-tetrazoles in good to excellent yields in short reaction times. The presence of beta-CD renders the formation of a precipitate-like gel in the reaction media when heated. No precipitation occurs in the absence of NaN3 and NH4Cl. The precipitation responses with other salts such as LiCl and NiCl2 were weaker than with NH4Cl. In the present paper the application of supramolecular aggregates is reported for the [2+3] cycloaddition reaction. beta-Cyclodextrin can be recovered and reused without any significant loss of activity.