Highly Efficient Synthesis of 5-Substituted 1H-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

• Published in: European Journal of Organic Chemistry Vol. 2011; no. 31; pp. 6343 - 6355
• Main Authors: Aridoss, Gopalakrishnan, Laali, Kenneth K.
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.11.2011; WILEY‐VCH Verlag; Wiley; Wiley-VCH
• Subjects: 15N NMR spectroscopy; 1H-Tetrazole synthesis; Chemistry; Chemistry, Organic; Cu/Zn alloy nanopowder; Cycloaddition; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Ionic liquids; Organic chemistry; Physical Sciences; Preparations and properties; Science & Technology; N-15 NMR spectroscopy; MONO; Cu/Zn alloy nanopowder; ENERGETIC SALTS; AZIDE; Cycloaddition; SOLVENTS; NITRILES; 1H-Tetrazole synthesis; NITROGEN-RICH SALTS; ORGANIC-COMPOUNDS; Ionic liquids; AROMATICS; LIFE; Tetrazole derivatives; Catalytic reaction; N NMR spectroscopy; Nitrogen 15; Nitrogen heterocycle; NMR spectrometry; Ionic liquid; Sodium Azides; Nanopowder; Chemical synthesis; Zinc alloy; Copper alloy
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201100957

A series of 5‐substituted 1H‐tetrazoles were synthesized through [3+2] cycloaddition reactions between nitriles RCN and NaN3 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 EtSO4–, OTf–, and NTf2– 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 NTf2 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 15N and 1H/15N correlations. Synthesis of a host of 5‐substituted 1H‐tetrazoles through [3+2] cycloadditions between nitriles RCN and NaN3 in the presence of Cu–Zn alloy nanopowder as catalyst, together with the preparation of their N‐alkylated derivatives, became the starting point for the synthesis and detailed NMR studies of new tetrazole‐based ionic liquids (ILs) with EtSO4–, OTf–, and NTf2– counterions.