Synthesis
GENERAL METHODS: 5-(4-chlorophenyl)-1H-tetrazole (2c) was synthesized as follows: 4-chlorobenzonitrile (1c, 274 mg, 2 mmol), NaN3 (260 mg, 4 mmol), Sc(OTf)3 (197 mg, 0.4 mmol), and 8 mL of a 3:1 isopropanol-water mixture were added to a 30 mL Pyrex microwave reaction tube , which was sealed. The reaction tube was placed in a Milestone Start Synth microwave reactor and heated at 160°C for 1 h with magnetic stirring. The progress of the reaction was monitored by thin layer chromatography (TLC) using a solvent mixture of ether-hexane (50:50) as the unfolding agent. Upon completion of the reaction, the reaction mixture was diluted with 20 mL of saturated aqueous sodium bicarbonate and extracted with 215 mL of ethyl acetate. The aqueous phase was acidified with concentrated hydrochloric acid to pH ≤ 2 under ice bath cooling, followed by extraction of the precipitate with 315 mL of ethyl acetate. The organic phases were combined, dried with anhydrous sodium sulfate and transferred to a weighed round bottom flask. The organic phase was concentrated by rotary evaporation under reduced pressure at 40°C and then further dried under high vacuum. The product was purified by recrystallization from ethyl acetate and hexane. All reagents were used directly without purification. Nuclear magnetic resonance (NMR) spectra were determined on a 300 MHz (1H) and 75 MHz (13C) NMR instrument.1H NMR spectra were determined in dimethylsulfoxide (DMSO-d6) with DMSO (2.52 ppm) as an internal standard; 13C NMR spectra were determined in DMSO-d6 with DMSO (40.5 ppm) as an internal standard. Infrared (IR) spectra were determined by Fourier transform infrared (FTIR) spectrophotometer. The melting point of the solid product was determined by melting point apparatus.5-(4-Chlorophenyl)-1H-tetrazole (2c) was a white solid with IR (KBr pressed) νmax/cm-1 : 3385 (broad peak), 1645 (mid), 1634 (mid); 1H NMR (DMSO-d6, δ): 11.60 (broad peak, 1H), 8.07 (d, J=8.28 Hz. 2H), 7.70 (d, J=8.25 Hz, 2H); 13C NMR (DMSO-d6, δ): 155.8 (broad peak), 136.9, 130.6, 129.7, 124.1; melting point 250-251°C.
References
[1] Journal of the Brazilian Chemical Society, 2012, vol. 23, # 12, p. 2197 - 2203
[2] Journal of Organic Chemistry, 2012, vol. 77, # 23, p. 10882 - 10890
[3] Tetrahedron Letters, 2014, vol. 55, # 44, p. 6034 - 6038
[4] Asian Journal of Chemistry, 2017, vol. 29, # 4, p. 864 - 866
[5] Chemical Communications, 2010, vol. 46, # 3, p. 448 - 450
