Hydrochloric Acid → 8-Butyl-2-(2-methoxyphenyl)-5,6,7,8-tetrahydro-imidazo[1,2-a]pyrazine

HRID 901117Notes

Reaction equation

HRID 901117 reaction equation
[CH2:1]([C:5]1[C:6]2[N:7]([CH:12]=[C:13]([C:15]3[CH:20]=[CH:19][CH:18]=[CH:17][C:16]=3[O:21][CH3:22])[N:14]=2)[CH2:8][C:9](=O)[N:10]=1)[CH2:2][CH2:3][CH3:4].B.C1COCC1.Cl.C([O-])([O-])=O.[K+].[K+]>C1COCC1>[CH2:1]([CH:5]1[NH:10][CH2:9][CH2:8][N:7]2[CH:12]=[C:13]([C:15]3[CH:20]=[CH:19][CH:18]=[CH:17][C:16]=3[O:21][CH3:22])[N:14]=[C:6]12)[CH2:2][CH2:3][CH3:4]

Participants

6

Reactant 4

HCID 313Hydrochloric AcidHCID 11430Potassium CarbonateHCID 2723981Borane;tetrahydrofuranHCID 220168358-Butyl-6-oxo-2-(2-methoxyphenyl)-imidazo[1,2-a]pyrazine

Product 1

HCID 220168108-Butyl-2-(2-methoxyphenyl)-5,6,7,8-tetrahydro-imidazo[1,2-a]pyrazineYield 92%

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent

Procedure

The product from Step 1.e. (6.13 g, 20.5 mmol) (compound vi where R3 is n-butyl, R4 is 2-methoxyphenyl, and R5 and R6 are H) was dissolved in THF (100 ml) and treated with 1M BH3/THF (82.0 ml, 82.0 mmol) at room temperature for about 2 hours and then refluxed for about 3 hours. The mixture was cooled to room temperature and 4N HCl (50 ml) was added dropwise. The mixture was stirred at room temperature for about 2 hours then made basic by careful portionwise addition of solid K2CO3. Product was extracted with EtOAc (3×50 ml). The EtOAc layers were combined, dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was dissolved in MeOH (about 50 ml), concentrated HCl (1.75 ml) was added and the solution was again concentrated under reduced pressure. The product was crystallized from MeOH/Et2O to yield 6.76 g (92%) of the desired product. Mass spec. 286.3 MH′, NMR (300 MHz, DMSO-d6, 30° C.) 10.0-11.5 (2H, s broad), 8.05-8.15 (1H, d,d), 8.0-8.1 (1H, s), 7.35-7.5 (1H, t), 7.15-7.3 (1H, d), 7.0-7.15 (1H, t), 4.8-4.95 (1H, m), 4.4-4.65 (2H, m), 3.9-4.0 (3H, s), 3.65-3.8 (1H, m), 3.5-3.65 (1H, m), 2.45-2.65 (1H, m), 2.1-2.35 (1H, m), 1.5-1.7 (2H, m), 1.25-1.5 (2H, m), 0.85-1.0 (3H, t).

Workup

  1. temperaturerefluxed for about 3 hours
  2. extractionProduct was extracted with EtOAc (3×50 ml)
  3. dry with materialdried over Na2SO4
  4. filtrationfiltered
  5. concentrationconcentrated under reduced pressure
  6. dissolutionThe residue was dissolved in MeOH (about 50 ml)
  7. additionconcentrated HCl (1.75 ml) was added
  8. concentrationthe solution was again concentrated under reduced pressure
  9. customThe product was crystallized from MeOH/Et2O

Sources & evidence

ORD record
ord-4e7d549734dd48289f36f9e711a68c3b
Source dataset
uspto-grants-2008_04
Patent number
US07361656B2

Reaction notes

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