[Cl:1][C:2]1[N:7]=[CH:6][C:5]([NH:8][C:9](=[O:15])[O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[C:4](I)[CH:3]=1.[C:17]([CH:19]1[CH2:22][CH2:21][CH2:20]1)#[CH:18]>CCN(CC)CC.C1COCC1.O.Cl[Pd](Cl)([P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)[P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.[Cu]I>[Cl:1][C:2]1[N:7]=[CH:6][C:5]([NH:8][C:9](=[O:15])[O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[C:4]([C:18]#[C:17][CH:19]2[CH2:22][CH2:21][CH2:20]2)[CH:3]=1
To the solution of tert-butyl 6-chloro-4-iodopyridin-3-ylcarbamate (7.0 g, 19.8 mmol) in Et3N (100 mL) was added the solution of ethynylcyclobutane in THF (prepared in step a), Pd(PPh3)2Cl2 (1.8 g, 2.1 mmol) and CuI (400 mg, 2.1 mmol). The reaction mixture was stirred at 25° C. for 16 h. The mixture was diluted with water and extracted with dichloromethane (3×100 mL). The extract was washed with brine, dried, concentrated in vacuo and purified by chromatography on silica gel (5-10% ethyl acetate in petroleum ether as eluant) to afford tert-butyl 6-chloro-4-(cyclobutylethynyl)pyridin-3-ylcarbamate (3.6 g, 60% yield). 1H NMR (300 MHz, CDCl3) δ: 9.11 (br, s, 1H), 7.22 (s 1H), 6.97 (s, 1H), 3.39-3.25 (m, 1H), 2.48-1.98 (m, 6H), 1.52 (s, 9H).
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