Highly Efficient Synthesis of 5‐Substituted 1<i>H</i>‐Tetrazoles Catalyzed by Cu–Zn Alloy Nanopowder, Conversion into 1,5‐ and 2,5‐Disubstituted Tetrazoles, and Synthesis and NMR Studies of New Tetrazolium Ionic Liquids

Abstract

Abstract A series of 5‐substituted 1 H ‐tetrazoles were synthesized through [3+2] cycloaddition reactions between nitriles RCN and NaN 3 in the presence of Cu–Zn alloy nanopowder as catalyst. The 1,5‐dibutyl, 1‐butyl‐5‐hexyl, 2,5‐dibutyl, and 2‐butyl‐5‐hexyl derivatives were then used as building blocks to synthesize several novel tetrazolium ionic liquids (ILs) with EtSO 4 – , OTf – , and NTf 2 – counterions. Whereas alkylation of the 2,5‐dialkyltetrazoles selectively gave the N‐4 alkylated onium salts, with the 1,5‐dialkyl derivatives approximately 1:1 mixtures of two tetrazolium salts were formed by alkylation at N‐3 and N‐4. The triflate and ethyl sulfate salts are room‐temperature ILs that are hydrophilic, whereas the NTf 2 salts are low‐melting ILs and are hydrophobic. The resulting tetrazolium‐based ionic liquids were studied by various multinuclear and 2D NMR techniques including natural abundance 15 N and 1 H/ 15 N correlations.