Dimethylformamide → 4-Chloro-7-methyl-2-oxo-1,5-diphenyl-1,2,5,8-tetrahydro-pyrido[2,3-d]pyrimidine-6-carboxylic acid ethyl ester

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Reaction Steps

The compound from step 5 (11 g, 27.3 mmol) was taken in 100 ml dry chloroform and then charged with DMF (dimethylformamide) (2 ml, 27 mmol). POCl3 (14 ml) was dissolved in advance in 26 ml chloroform and was added under stirring in an argon atmosphere. The reaction mixture was then stirred at 70 C for 6 h. The reaction was monitored by LC-MS. The reaction mixture was cooled down to room temperature and poured into 25% ice cold solution of potassium acetate (150 ml) under vigorous stirring, organic phase was separated, aqueous phase was extracted with DCM (dichloromethane) (2×100 ml) and the combined organic solution was dried over magnesium sulfate and then the solvent was evaporated under vacuum yielding yellow solids (8.3 g, 19.7 mmol, 72%).

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