To a suspension of NaH (60% in mineral oil, 36 mg) in 8 mL of dimethylformamide was added 2-amino-6-(2,6-dichlorophenyl)-pyrido[2,3-d]pyrimidin-7(8H)-one (205 mg, 0.67 mmol). The mixture was heated at 60° C. for 20 minutes resulting in a clear solution. 1-Iodo-2-methylpropane (110 μL, 0.94 mmol) was added, and the solution was stirred at 50° C. for 30 minutes. An additional amount of 1-iodo-2-methylpropane (40 μL, 0.34 mmol) was added, and the solution was stirred at 50° C. for 40 minutes, then cooled to room temperature and poured onto 40 mL of ice water. The resulting precipitate was removed by filtration and washed with water. The gummy residue was dissolved in ethyl acetate and washed with water. The organic layer was dried over magnesium sulfate, filtered, and concentrated in vacuo. The resulting solid was purified by flash chromatography, eluting with 1:1 hexane:ethyl acetate to provide 123 mg (51%) of 2-amino-6-(2,6-dichlorophenyl)-8-isobutyl-8H-pyrido[2,3-d]pyrimidin-7-one; mp 193°-195° C.
