Hydrazine → 2-[4-(4-Amino-phenylethynyl)-1H-pyrazol-3-yl]-4-chloro-phenol

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To a mixture of 6-chloro-3-iodo-chromone (1A, 6.12 g, 20 mmol) and 4-ethynylaniline (2.32 g, 24 mmol) and PdCl2(PPh3)2 (0.28 g, 0.4 mmol) and CuI (38 mg, 0.2 mmol) was added anhydrous CH3CN (200 mL). Upon stirring, diisopropylethylamine (DIPEA, 14 mL, 80 mmol) was added slowly to the above mixture. The reaction mixture was stirred at rt for 7 h. LCMS indicated all of 1A was consumed. Anhydrous hydrazine (5.3 mL, 80 mmol) was then added. The mixture was stirred at rt overnight. Solvent was removed. The residua was dissolved in dichloromethane and loaded onto a silica column eluting with dichloromethane/ethyl acetate (v/v 6/1, 2/1, 1/1, 1/2, 1/5) to afford the title compound 24A (3.02 g) as a yellowish solid in 48.7% yield. 1H NMR (CDCl3, 500 MHz) δ 10.05 (br s, 1H), 8.75 (d, 1H, J=2.0 Hz), 7.84 (s, 1H), 7.42 (d, 2H, J=8.5 Hz), 7.20 (dd, 1H, J=9.0, 2.0 Hz), 6.98 (d, 1H, J=8.5 Hz), 6.68 (d, 2H, J=8.0 Hz), 3.86 (s, 2H). LCMS (ESI) m/z 310.07 (MH+, 100); HPLC: tR=3.78 min.

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