6-Iodo-3-(o-tolyl)-[1,2,4]triazolo[4,3-a]pyridine (10)

To a suspension of hydrazine 8 (875 mg, 3.72 mmol) in EtOH (12 mL) was added 2-methylbenzaldehyde (447 mg, 3.72 mmol). The mixture was heated to reflux for 2 h, then cooled to room temperature. The resulting solid was filtered and washed with EtOH to give the hydrazone 9. To a suspension of the crude hydrazone 9 in anhydrous CH₂Cl₂/MeOH (10:2, 19 mL) was added (diacetoxyiodo)benzene (1.68 g, 5.21 mmol) at 0°C. The mixture was stirred at room temperature overnight, then diluted with water, extracted with CH₂Cl₂ and dried over anhydrous Na₂SO₄. The crude product was purified using flash column chromatography to give the triazolopyridine 10 (748 mg, 2.23 mmol, 60%) as an off-white solid. ¹H NMR (500 MHz, CDCl₃) δ 8.03 (t, J = 1.3 Hz, 1H), 7.61 (dd, J = 9.6, 1.0 Hz, 1H), 7.47 (td, J = 7.5, 1.5 Hz, 1H), 7.44–7.39 (m, 3H), 7.37 (t, J = 7.4 Hz, 1H), 2.25 (s, 3H); ¹³C NMR (125 MHz, CDCl₃) δ 148.5, 145.8, 138.7, 135.1, 131.3, 130.8, 130.2, 127.6, 126.4, 125.0, 117.5, 77.7, 19.9; m/z (ESI⁺) 336.0 ([M + H]⁺, 100%); HRMS (ESI⁺) C₁₃H₁₁N₃I⁺ ([M + H]⁺) requires 335.9992; found 335.9988.