5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

Synthesis Of 5-substituted 1h-tetrazoles Catalyzed By Zeolite Modified With Copper Oxide Nanoparticles

Tetrazoles have a wide range of biological and pharmaceutical applications. Synthetic tetrazole derivatives have been demonstrated to possess antifungal [1], antidiabetic [2] antibiotic, anti-allergic, antagonists, antihypertensive, antiviral and anti HIV activities [3-5]. many methods have been reported for the synthesis of 5-substituted 1H-tetrazole. Many of these reactions were carried out in the presence of various Lewis acid catalysts such as AlCl3 [6], ZnO [7], Cu2O [8], FeCl3/SiO2 [9], CdCl2 [10], COY zeolites [11] CuFe2O4 nanoparticles [12]. Becuase of the great applications of tetrazole-based structures, synthetic procedures are still worth exploring. In many of these methods, 5-substituted 1H-tetrazoles have been synthesized from the reaction of various nitriles but some of them are toxic and also expensive. Hence the use of less expensive and more available starting materials is very important for the efficient and facial synthesis of 5-substituted 1H-tetrazoles. In this work we report a simple, efficient and inexpensive strategy for the synthesis of 5-substituted 1H-tetrazoles from various aldoximes and sodium azide using zeolite/copper oxide (CuO) nanocomposites (NCs) as a reusable catalyst. copper oxide (CuO) NP-based zeolites were prepared according to the previously described methodology [13]. The prepared NCs were characterized using various techniques: X-ray diffraction (XRD) and Field emission scanning electron microscopy (FE-SEM). The synthesis of tetrazoles was accomplished by the addition of the zeolite/copper oxide (CuO) nanocomposites (NCs) (0.05 gr) to a stirred mixture of various aldoximes (1 mmol) in DMF (5 mL) at 120 °C. After 15 min the sodium azide (1.5 mmol) was added to the reaction mixture. The progress of the reaction was monitored by TLC (Thin Layer Chromatography). After completion, the reaction mixture was cooled and then H2O (10 mL) and 3N HCl (5 mL) were added, and an extraction with ethyl acetate was performed. The nanocatalyst was easily separated with the filtration and reused. The organic layer was separated, washed with distilled water, dried over anhydrous sodium sulfate, and concentrated to give the crude solid 5-phenyl-1H-tetrazoles (Scheme 1). The crude product was recrystallized from n-hexane:ethylacetate. All obtained products are known compounds and were characterized on the basic of spectral data (1H NMR, FT-IR spectra) and were identified by comparing their melting points with those of authentic samples. For instance, the 5-Phenyl-1H-tetrazole was obtained as a white solid with: melting point 213-214 ºC; FT-IR (KBr) νmax/cm-1: 3117, 3043, 2990, 2836, 2760, 2557, 2460, 1611, 1540, 1385 and 1H NMR (400 MHz, DMSO-d6) δ 7.53-8.01 (m, 5H, Ph). The advantages and profits of this method are the replacement of the toxic nitriles with aldoximes, moderate to good yields and simple work up.
Azam Karimian