Water → 6,7-Dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid

HRID 1697461Notes

Reaction equation

HRID 1697461 reaction equation
C([O:3][C:4]([C:6]1[CH:7]=[N:8][N:9]2[CH2:14][CH2:13][CH2:12][O:11][C:10]=12)=[O:5])C.O>O1CCCC1.C(O)C.[OH-].[Li+]>[N:8]1[N:9]2[C:10]([O:11][CH2:12][CH2:13][CH2:14]2)=[C:6]([C:4]([OH:5])=[O:3])[CH:7]=1

Participants

6

Reactant 2

HCID 962WaterHCID 52228126Ethyl 6,7-dihydro-5H-pyrazolo[5,1-B][1,3]oxazine-3-carboxylate

Product 1

HCID 522281256,7-Dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acidYield 98.2%

Reagents, catalysts & solvents 3

HCID 702EthanolSolventHCID 3939Lithium HydroxideSolventHCID 8028TetrahydrofuranSolvent

Procedure

A solution of 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid ethyl ester (9.67 g, 49.3 mmol) in tetrahydrofuran (150 mL), ethanol (50 mL) and 1M of lithium hydroxide in water (148 mL, 148 mmol) was stirred at 60° C. for 2 days. After cooling, the volatiles were removed. The residue was transferred to an Erlenmeyer flask and ice was added. The reaction was acidified to pH 2 with 10M HCl. The aqueous layer was extracted several times with 3/1 chloroform/IPA. The combined organic layers were dried (Na2SO4), filtered, concentrated to afford the acid as a solid (8.14 g, 98%). 1H NMR (400 MHz, DMSO-d6) δ7.57 (s, 1H), 4.37 (t, 2H, J=5.29 Hz), 4.07 (t, 2H, J=6.11 Hz), 2.20-2.15 (m, 2H).

Workup

  1. temperatureAfter cooling
  2. customthe volatiles were removed
  3. additionwas added
  4. extractionThe aqueous layer was extracted several times with 3/1 chloroform/IPA
  5. dry with materialThe combined organic layers were dried (Na2SO4)
  6. filtrationfiltered
  7. concentrationconcentrated

Sources & evidence

ORD record
ord-7869042bf4d7427ea47f73ea892e6b23
Source dataset
uspto-grants-2012_04
Patent number
US08163901B2

Reaction notes

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