71607-28-8

A new acid molten salt was prepared and its structure elucidation was conducted by FTIR, 1D NMR, 2D NMR, and mass spectrometry. Further support to elucidate the chemical structure of the 1H,4H-piperazine-N,N′-diium ring of the new acid molten salt was achieved by1H and13C NMR, and COSY analyses of 1H,4H-piperazine-N,N′-diium dibromide, which is synthesized and characterized for the first time in the current work. The analysis of FTIR and NMR spectra as well as pH and titrimetric analysis excluded the formation of [SO4]2?and the presence of an excess of H2SO4. Moreover, no distinguishing peak was detected for the acid proton of [HSO4]?in DMSO-d6. The thermal phase transition and thermal stability of the acid molten salt were also recorded, which approved the strong interaction between a dication and hydrogen sulfate anions. According to the acidity of the new molten salt, we encourage the study of its catalytic activity for the acetylation ofn-pentanol using glacial acetic acid. Pentyl acetate was obtained in 89.0% conversion and 78.0% isolated yield. The1H NMR spectrum of the residue showed an excess of HOAc together with molten salt, whereas the1H NMR spectrum of the upper phase exhibited pure pentyl acetate. After separation of the upper phase, the residue was concentrated and used in the next run without further purification. No significant changes in the chemical structure and catalytic activity of the new molten salt were observed even after the 5th run. Two chiral alcohols, including (?)-menthol and (+)-borneol, as well as α-tocopherol (α-TCP) were also acetylated with acetic acid in the presence of the new acid molten salt under optimized reaction conditions, which afforded the desired acetates in high yields.

Background: Tetrazoles are imperative nitrogen rich heterocyclic compounds with a wide range of applications in the field of organic synthesis, coordination chemistry, material sciences, and medicinal chemistry. A most common approach for the synthesis of 5-substituted-1H-Tetrazoles is achieved by [3+2] cycloaddition reaction of azides to nitriles. In this paper a new acidic ionic liquid is introduced as a catalyst to promote the mentioned reaction. Methods: Piperazinium dihydrogen sulfate:as a new acidic ionic compound was obtained by treatment of piperazine with sulfuric acid, which is further was applied as a catalyst for the [3+2] cycloaddition reaction of azides to organic nitriles. Results: The [3+2] cycloaddition reaction of sodium azide with structurally different organic nitriles using only 1.5 mol% of the piperazinium dihydrogen sulfate proceeded well at 100°C and 5-substituted-1H-Tetrazoles were prepared in good to excellent yields. Herein, piperazinium dihydrogen sulfate has a dual role of catalyst and reaction medium, which circumvents the use of any organic solvent. The catalyst is also recyclable. This method is particularly suitable for benzonitriles carrying deactivating groups which furnished the corresponding products in excellent yields. By this method, mono [3+2] cycloaddition product of dicyanides was obtained. Conclusion: In conclusion, piperazinium dihydrogen sulfate as a new acidic ionic compound was applied to promote synthesis of 5-substituted-1H-Tetrazoles through [3+2] cycloaddition reaction of organic nitriles with sodium azide. This new ionic compound can be easily separated from the reaction mixture which resulted to a simple work-up of the products.