Boron tribromide → Robustaflavone

HRID 1976353Notes

Reaction equation

HRID 1976353 reaction equation
C[O:2][C:3]1[CH:8]=[CH:7][C:6]([CH:9]2[O:19][C:18]3[C:13](=[C:14]([O:45]C)[C:15]([C:22]4[CH:27]=[C:26]([CH:28]5[O:38][C:37]6[C:32](=[C:33]([O:41]C)[CH:34]=[C:35]([O:39]C)[CH:36]=6)[C:30](=[O:31])[CH2:29]5)[CH:25]=[CH:24][C:23]=4[O:43]C)=[C:16]([O:20]C)[CH:17]=3)[C:11](=[O:12])[CH2:10]2)=[CH:5][CH:4]=1.B(Br)(Br)Br>>[CH:5]1[C:6]([C:9]2[O:19][C:18]3[CH:17]=[C:16]([OH:20])[C:15]([C:22]4[CH:27]=[C:26]([C:28]5[O:38][C:37]6[CH:36]=[C:35]([OH:39])[CH:34]=[C:33]([OH:41])[C:32]=6[C:30](=[O:31])[CH:29]=5)[CH:25]=[CH:24][C:23]=4[OH:43])=[C:14]([OH:45])[C:13]=3[C:11](=[O:12])[CH:10]=2)=[CH:7][CH:8]=[C:3]([OH:2])[CH:4]=1

Participants

3

Reactant 2

HCID 25134Boron tribromideHCID 497894HCID 497894, compound

Product 1

HCID 5281694RobustaflavoneYield 30%

Procedure

To a solution of 10 (75.0 mg, 0.12 mmol) in 10 mL dry CHC3 was added BBr3 (1.0 M in CH2Cl2, 1.45 mL, 1.45 mmol), and the resulting yellow slurry was stirred at reflux overnight. The reaction mixture was cooled to room temperature, quenched by the careful addition of MeOH, and evaporated in vacuo. The resulting orange solid was triturated with MeOH, the solvent again evaporated in vacuo, and the solid was partitioned between EtOAc and 1 M NaOH. The organic layer was discarded, and the aqueous layer was extracted with EtOAc. After cooling to 0° C., the aqueous layer was carefully acidified to pH 3.0 by the dropwise addition of 3 M HCl. The resulting yellow precipitate was collected by vacuum filtration, rinsed with water and air dried (38.7 mg). The crude material was chromatographed through silica gel, eluting with a mixture of toluene/pyridine/formic acid (20:10:1). Appropriate fractions were combined and evaporated to afford 19.4 mg (30.0%) robustaflavone. An analytical sample was obtained via recrystallization from pyridine/H2O (1:1); mp 370-372° C., dec. (lit.1 mp 350-352° C.). Spectral data of synthetic robustaflavone was identical to that recently reported1 for the natural product isolated from Rhus succedanea. Anal. calcd for C30H18O10.1.25 H2O: C, 64.23; H, 3.68. Found: C, 64.17; H, 3.68.

Workup

  1. temperatureat reflux overnight
  2. customquenched by the careful addition of MeOH
  3. customevaporated in vacuo
  4. customThe resulting orange solid was triturated with MeOH
  5. customthe solvent again evaporated in vacuo
  6. customthe solid was partitioned between EtOAc and 1 M NaOH
  7. extractionthe aqueous layer was extracted with EtOAc
  8. temperatureAfter cooling to 0° C.
  9. additionthe aqueous layer was carefully acidified to pH 3.0 by the dropwise addition of 3 M HCl
  10. filtrationThe resulting yellow precipitate was collected by vacuum filtration
  11. washrinsed with water and air
  12. customdried (38.7 mg)
  13. customThe crude material was chromatographed through silica gel
  14. washeluting with a mixture of toluene/pyridine/formic acid (20:10:1)
  15. customevaporated

Sources & evidence

ORD record
ord-585adadbe541464297990ffb5b90ea69
Source dataset
uspto-grants-2001_05
Patent number
US06225481B1

Reaction notes

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