Hydrochloric Acid → (5R,7R)-7-fluoro-5-methyl-4-(piperazin-1-yl)-6,7-dihydro-5H-cyclopenta[d]pyrimidine dihydrochloride

Participants

Reaction Conditions

Reaction Steps

tert-Butyl 4-((5R,7S)-7-hydroxy-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazine-1-carboxylate (0.843 g, 2.521 mmol) was dissolved in methylene chloride (40 mL) and cooled to −20° C. The solution was treated with DAST (0.9992 mL, 7.562 mmol) and stirred at −20° C. for 100 minutes. After 3 hours, the reaction was quenched with ice and then warmed to ambient temperature. The mixture was separated. The aqueous phase (pH of about 1) was extracted with methylene chloride (2×), and the combined organics were washed with 6% NaHCO3 (2×), dried over Na2SO4, and concentrated to a dark oil (0.91 g). This material was chromatographed on SiO2 (Biotage 40S, load with eluant) and eluted with 2:1 hexane/EtOAc. The desired tert-butyl 4-((5R,7R)-7-fluoro-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazine-1-carboxylate (0.6138 g, 72%) was recovered cleanly. tert-Butyl 4-((5R,7R)-7-fluoro-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazine-1-carboxylate (0.6138 g, 1.825 mmol) was dissolved in dioxane (5 mL) and cooled to 0° C. A solution of HCl in dioxane (11.40 mL, 45.61 mmol; 4M) was added dropwise, and then the reaction mixture was allowed to warm to ambient temperature while stirring for 60 hours. The reaction mixture was concentrated in vacuo, re-suspended in MeOH and re-concentrated (3×). The residue was dissolved in MeOH (3.7 mL) and added dropwise to a rapidly stirring flask containing ether (100 mL). The white solid was filtered under a blanket of nitrogen gas, washed with ether and dried under nitrogen gas to give (5R,7R)-7-fluoro-5-methyl-4-(piperazin-1-yl)-6,7-dihydro-5H-cyclopenta[d]pyrimidine dihydrochloride as a white solid (539 mg, 96%). LC/MS (APCI)+ m/z 237.2.

Provenance & Evidence