1,4-Dioxane hydrochloride → HCID 24786151, compound

4M HCl/dioxane (7.83 ml, 31.3 mmol) was added to a slightly cloudy solution of tert-butyl (S)-2-(4-chlorophenyl)-3-(4-((R)-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazin-1-yl)-3-oxopropyl(isopropyl)carbamate (0.679 g, 1.25 mmol) in dioxane (8 mL). The reaction mixture was stirred overnight under nitrogen (16 hours). The reaction mixture was concentrated to dryness and dried on a high vacuum line. The resulting residue was dissolved in minimal MeOH, and the solution was added dropwise to a stirring solution of ether, which caused a white precipitate to form. The resulting precipitate was isolated by filtration through a medium frit funnel with nitrogen pressure, rinsed with ether, dried with nitrogen pressure, dried in vacuo and then further in a 55° C. high vacuum oven for 2 days to give (S)-2-(4-chlorophenyl)-3-(isopropylamino)-1-(4-((R)-5-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-yl)piperazin-1-yl)propan-1-one dihydrochloride (0.610 g, 94.6% yield) as a white powder.