Regio-selective synthesis of 5-substituted 1H-tetrazoles using ionic liquid [BMIM]N3 in solvent-free conditions: a click reaction

Soheila Khaghaninejad,Mehdi Bakavoli,Tayebeh Hosseinnejad,Majid M Heravi,Hossein A Oskooie

doi:10.1007/s11164-015-2105-3

Soheila Khaghaninejad, Mehdi Bakavoli + Show 3 more

Open Access

https://doi.org/10.1007/s11164-015-2105-3

Copy DOI

Abstract

A multi-component, one pot and regio-selective synthesis of different 5-substituted 1H-tetrazoles was successfully accomplished via a click reaction. In this respect, we have performed the reaction of either isatins or various aromatic aldehydes with malononitrile and ionic liquid, 1-butyl-3-methylimidazolium azide ([BMIM]N3), as a relatively green source of azide mediated by o-phthalimide-N-sulfonic acid (OPNSA). The calculated thermodynamic results demonstrate a reliable agreement with our experimentally observed regio-selectivity. From the electronic viewpoint, we have also assessed the nature of regio-selectivity via quantum theory of atoms in molecule analysis.

Highlights

We have performed the reaction of either isatins or various aromatic aldehydes with malononitrile and ionic liquid, 1-butyl-3-methylimidazolium azide ([BMIM]N3), as a relatively green source of azide mediated by o-phthalimide-N-sulfonic acid (OPNSA)
In continuation of our efforts to improve the eco-compatibility of organic processes, is the synthesis of 5-substituted 1H-tetrazoles
We initially focused on a previously reported three-component reaction, involving isatin, (1a), (2), and sodium azide, leading to 5-substituted 1Htetrazoles [6]

Summary

Introduction

Several methodology are on hand for the synthesis of 5-substituted 1H-tetrazoles, based on click reactions using various catalysts and different conditions, such as InCl3 DMF/microwave heating [27], TMSN3/ TBAFÁ3H2O, solventless/50–120 °C [28], TMSN3/Fe(OAc)2/DMF-H2O/80 °C [13], R2AlN3/toluene/-40–120 °C [29], CoY/DMF/120 °C [30], MBA-ZnO/ DMSO/120–130 °C [31], Cu2O/DMF-MeOH/80 °C [9], CuFe2O4/DMF/120 °C [32], NaN3/Cu–Zn alloy nanopowder/DMF/90–135 °C [33], NaN3/zeolite and zirconia/DMF and H2O/reflux [34], ionic liquids (ILs)/100 °C [35], AcOH/NMPH2O/microwave [12], montmorilloniteK10/microwave [36], HOAc/ILs/microwave heating [15], Et3NÁHCl/PhNO2/microwave [37], and montmorillonite K10-M (M = Fe, Zn, Cu, Ni)/DMF/reflux [38] These methods have their own merits and drawbacks. We try our best to comply with the disciplines of green chemistry and bring them to practice in our Armed with these experiences, in this paper we wish to report a relatively green method for the regio-selective synthesis of 5-substituted 1H-tetrazoles using (3) as a relatively safe azide source, in the presence of o-phthalimide-N-sulfonic acid (OPNSA) [65] as a solid acid catalyst under solvent-free conditions. We confirmed the already claimed regio-selectivity of these reactions by computational quantum chemistry approaches

Results and discussion

H NC N N

Conclusion