Acetic Acid → 6-Bromo-3,4-dihydro-4-methyl-2(1H)-quinoxalinone

HRID 44188Notes

Reaction equation

HRID 44188 reaction equation
[Br:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[NH:8][C:7](=[O:12])[CH2:6][NH:5]2.C=O.O.[C:16](O)(=O)C.[BH3-]C#N.[Na+]>CO>[Br:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[NH:8][C:7](=[O:12])[CH2:6][N:5]2[CH3:16]

Participants

7

Reactant 5

HCID 176Acetic AcidHCID 712FormaldehydeHCID 962WaterHCID 5003444Sodium cyanoborohydrideHCID 669113076-Bromo-1,2,3,4-tetrahydroquinoxalin-2-one

Product 1

HCID 226677406-Bromo-3,4-dihydro-4-methyl-2(1H)-quinoxalinoneYield 94%

Reagents, catalysts & solvents 1

HCID 887MethanolSolvent

Procedure

To a solution of 6-bromo-3,4-dihydroquinoxalin-2(1H)-one (370 mg, 1.63 mmol) in 10 ml methanol was added a solution of 37% formaldehyde in water (59 mg, 1.95 mmol) and acetic acid (196 mg, 3.26 mmol). The mixture was stirred at room temperature for 2 h, then refluxed for 1 h. After addition of NaBH3CN (307 mg, 4.89 mmol) stirring was continued for 2.5 h at room temperature. Then methanol was removed under vacuum. To the remaining mixture water was added. Then the solution was basified to pH 8-9 with an aqueous solution of sodium hydrogen carbonate and extracted several times with ethyl acetate. The combined organic layers were washed with brine, dried over MgSO4 and evaporated, affording 6-bromo-4-methyl-3,4-dihydroquinoxalin-2(1H)-one (369 mg, 1.53 mmol, 94%) as off-white solid.

Workup

  1. temperaturerefluxed for 1 h
  2. stirringstirring
  3. waitwas continued for 2.5 h at room temperature
  4. customThen methanol was removed under vacuum
  5. additionTo the remaining mixture water was added
  6. extractionextracted several times with ethyl acetate
  7. washThe combined organic layers were washed with brine
  8. dry with materialdried over MgSO4
  9. customevaporated

Sources & evidence

ORD record
ord-86985e36ee8640a9b09d1aba01aae0b8
Source dataset
uspto-grants-2013_09
Patent number
US08541404B2

Reaction notes

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