*4.4. 2-(Carboxy(4-phenyl-1H-1,2,3-triazol-1-yl)methyl)benzoic Acid (***15***)*

Ethyl 2-(1-azido-2-methoxy-2-oxoethyl)benzoate[20] **16** (526 mg, 2 mmol, 1 equiv.) and phenylacetylene (206 mg, 1 equiv.) were added to a suspension of CuI (27 mg, 7 mol. %) in dry toluene. The reaction mixture was stirred at 85 ◦C overnight. The solvent was evaporated, and the title compound was extracted with ethyl acetate (30 mL). The organic layer was washed with water (20 mL × 2) and brine (20 mL × 1) and then dried over Na2SO4. The solvent was evaporated and the resulting compound (ethyl 2-(2-ethoxy-2-oxo-1-(4-phenyl-1H-1,2,3-triazol-1-yl)ethyl)benzoate) was used in the next step without further purification. The obtained ester and KOH (560 mg, 5 equiv.) were dissolved in 30 mL of

30% aq.THF and stirred for 1 h at room temperature. Activated charcoal (**12g**) (powder -100 particle size (mesh)) was added to the resulting mixture and intensively stirred at room temperature for 0.5 h. Next, the solution was filtered through a layer of zeolite, and 3 N HCl was added to it until pH = 1. The target compound (**15**) was extracted into diethyl ether, and the organic layer was combined and dried over Na2SO4 and was evaporated.

Yield 601 mg, 93% (2 steps). Colorless amorphous solid. 1H NMR (400 MHz, DMSO-*d*6) *δ* 13.55 (s, 2H), 8.72 (s, 1H), 8.07–8.00 (m, 1H), 7.94–7.82 (m, 2H), 7.71–7.61 (m, 1H), 7.60–7.51 (m, 2H), 7.50–7.42 (m, 2H), 7.39–7.30 (m, 1H), 7.29–7.20 (m, 1H). 13C NMR (101 MHz, DMSO-*d*6) *δ* 169.0, 168.5, 146.6, 135.7, 133.1, 131.4, 130.9, 130.6, 129.5, 129.4, 129.2, 128.5, 125.7, 122.9, 63.7. HRMS (ESI/Q-TOF) *m*/*z*: [M + H+] <sup>+</sup> Calcd for C17H14N3O4 <sup>+</sup> 324.0979; Found 324.0974.
