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To a suspension of ammonium chloride (10.7 g, 200 mmol) in 250 mL of dry toluene. was added a 2 M solution of Al(CH3)3 (100 mL, 200 mmol) in toluene dropwise under nitrogen at 0° C. The resulting reaction mixture was stirred at rt until no more evolution of gas was observed and then 2-chloropyridine-4-carbonitrile (13.86 g, 100 mmol) was added. The mixture was stirred at 90° C. overnight. It was then cooled down to 0° C. and 300 mL of methanol were added with subsequent stirring for 1 h at rt. After filtration, the solid was washed with methanol for several times, the solution was evaporated to dryness under vacuum. The residue was washed with methanol to give 2-chloropyridine-4-carboximidamide. (18.3 g, 95%). 1HNMR δ (400 MHz, d6-DMSO): 8.70 (dd, J=4.8, 0.4 Hz, 1H), 8.00 (dd, 0.4 Hz, 1H), 7.84 (dd, J=5.2, 1.6 Hz, 1H), 7.80 (m, 1H), 7.53 (t, J=8.1 Hz, 1H); MS (ESI) m/z (M+H)+ 156.

1. customThe resulting reaction mixture
2. stirringThe mixture was stirred at 90° C. overnight
3. temperatureIt was then cooled down to 0° C.
4. stirringwith subsequent stirring for 1 h at rt
5. filtrationAfter filtration
6. washthe solid was washed with methanol for several times
7. customthe solution was evaporated to dryness under vacuum
8. washThe residue was washed with methanol