Lithium borohydride → benzyl tetrahydro-3-oxo-1H-oxazolo[3,4-a]pyrazine-7(3H)-carboxylate

HRID 582228Notes

Reaction equation

HRID 582228 reaction equation
C(O[C:9]([N:11]1[CH2:16][CH2:15][N:14]([C:17]([O:19][CH2:20][C:21]2[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=2)=[O:18])[CH2:13][CH:12]1[C:27]([O:29]C)=O)=[O:10])C1C=CC=CC=1.[BH4-].[Li+]>O1CCCC1>[C:21]1([CH2:20][O:19][C:17]([N:14]2[CH2:15][CH2:16][N:11]3[C:9](=[O:10])[O:29][CH2:27][CH:12]3[CH2:13]2)=[O:18])[CH:22]=[CH:23][CH:24]=[CH:25][CH:26]=1

Participants

4

Reactant 2

HCID 4148881Lithium borohydrideHCID 21847669(+/-)-Methyl N,N'-dibenzyloxycarbonylpiperazine-2-carboxylate

Product 1

HCID 53668532benzyl tetrahydro-3-oxo-1H-oxazolo[3,4-a]pyrazine-7(3H)-carboxylate

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent

Procedure

To a flask containing methyl N,N'-dibenzyloxycarbonylpiperazine-2-carboxylate (Step 2, 12.60 g, 30.60 mmol) and tetrahydrofuran (65 mL) at 0° C. under an inert atmosphere is added lithium borohydride (2 M in THF) (23.00 mL, 45.9 mmol). The solution is warmed to ambient temperature, stirred 19 hours, cooled to 0° C., and quenched with water (50 mL). The mixture is diluted with ethyl acetate (100 mL) and the pH is adjusted to 2 with 1N HCl. The layers are separated and the aqueous phase is extracted with ethyl acetate (50 mL). The organics are combined, washed with water (50 mL) and saline, dried over MgSO4, concentrated in vacuo, and chromatographed on silica gel (70-230 mesh, 500 g), eluting with hexane/ethyl acetate (50/50) then ethyl acetate (100). The appropriate fractions are combined (Rf =0.17, TLC, hexane/ethyl acetate, 50/50) and concentrated in vacuo to give the title compound, mp 85.5-86.5° C.

Workup

  1. temperaturecooled to 0° C.
  2. customquenched with water (50 mL)
  3. additionThe mixture is diluted with ethyl acetate (100 mL)
  4. customThe layers are separated
  5. extractionthe aqueous phase is extracted with ethyl acetate (50 mL)
  6. washwashed with water (50 mL) and saline
  7. dry with materialdried over MgSO4
  8. concentrationconcentrated in vacuo
  9. customchromatographed on silica gel (70-230 mesh, 500 g)
  10. washeluting with hexane/ethyl acetate (50/50)
  11. concentrationconcentrated in vacuo

Sources & evidence

ORD record
ord-929d91ae8b524363998cb097fea84771
Source dataset
uspto-grants-1999_07
Patent number
US05922707

Reaction notes

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