Diphenyl chlorophosphate → N8-[4-(tert-Butyl)-1,3-thiazol-2-yl]-2-{3-[(dimethylamino)carbonyl]piperidino}-4-oxo-4H-pyrido[1,2-a]pyrimidine-8-carboxamide

Participants

Reaction Steps

N8-[4-(tert-butyl)-1,3-thiazol-2-yl]-2,4-dioxo-3,4-dihydro-2 H-pyrido[1,2-a]-pyrimidine-8-carboxamide (301.9 mg, 0.88 mmol) was suspended in dimethylformamide (6 ml) and acetonitrile (12 ml), added dropwise with diisopropylethylamine (1.83 ml, 10.5 mmol) and diphenyl chlorophosphate (545.1 μl, 2.63 mmol) at −10° C. under an argon flow, and stirred at the same temperature for 5 minutes and at room temperature for 15 minutes. The reaction solution was cooled to −10° C. again, added dropwise with a solution of 3-[(dimethylamino)carbonyl]piperidine trifluoroacetic acid salt (1.18 g, 4.38 mmol) in dimethylformamide (5 ml), and stirred at room temperature for 1 hour and at about 80° C. for 2 hours. The reaction solution was heated to about 100° C., heated for 30 minutes with stirring, then added with diisopropylethylamine (1.83 ml, 10.5 mmol), and further heated at 100° C. for 3 hours and 30 minutes with stirring. After cooling, the solution was added with saturated aqueous sodium hydrogencarbonate and extracted with chloroform. The organic layer was washed with saturated brine and dried over anhydrous sodium sulfate and the solvent was evaporated. The residue was purified by silica gel column chromatography (chloroform→chloroform:methanol=50:1→20:1, v/v) and preparative TLC (chloroform:methanol=20:1, v/v) to obtain the title compound (85.9 mg, 20.3%) as yellow orange oil.

Provenance & Evidence