Hydrochloric Acid → 3-Benzyl-9-oxa-3,7-diazabicyclo[3.3.1]nonane

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Reaction Steps

1-Methyl-2-pyrrolidinone (10 mL) was added to mercaptoacetic acid di-lithium salt monohydrate (from part (a) above, 1.21 g, 10 mmol) and the mixture was stirred for 10 minutes at room temperature. 3-Benzyl-7-(4-nitrophenylsulfonyl)-9-oxa-3,7-diazabicyclo[3.3.1]nonane (2 g, 5 mmol, see Example 2 above) was added and the mixture stirred at room temperature under nitrogen for 2.5 hours. Toluene (8 mL) and 2-propanol (15 mL) were added to the bright orange reaction solution. The internal temperature was adjusted to 40-45° C. A solution of hydrogen chloride in 2-propanol (10 mL, approx. 4M) was added dropwise whilst maintaining the above internal temperature range. Stirring was continued for 30 minutes in this temperature range. A white precipitate formed and the mixture was cooled slowly to room temperature with stirring. The mixture was stirred overnight and then cooled in an ice/water bath to 7° C. The precipitate was collected by filtration, washed with 2-propanol (2×5 mL) and sucked dry on the filter to give the title compound as a white powder (1.28 g, 88%).

Provenance & Evidence