Boron tribromide → 2H-1-Benzopyran-2-one, 5-hydroxy-

HRID 2399351Notes

Reaction equation

HRID 2399351 reaction equation
CO[C:3](=[O:16])[CH:4]=[CH:5][C:6]1[C:11]([O:12]C)=[CH:10][CH:9]=[CH:8][C:7]=1[O:14]C.B(Br)(Br)Br.C(=O)([O-])O.[Na+]>C(Cl)(Cl)Cl.C(Cl)Cl.C(OCC)(=O)C>[OH:12][C:11]1[CH:10]=[CH:9][CH:8]=[C:7]2[C:6]=1[CH:5]=[CH:4][C:3](=[O:16])[O:14]2

Participants

7

Reactant 3

HCID 25134Boron tribromideHCID 516892Sodium BicarbonateHCID 54202851Methyl 3-(2,6-dimethoxyphenyl)prop-2-enoate

Product 1

HCID 53181792H-1-Benzopyran-2-one, 5-hydroxy-Yield 89.6%

Reagents, catalysts & solvents 3

HCID 6212ChloroformSolventHCID 6344DichloromethaneSolventHCID 8857Ethyl AcetateSolvent

Procedure

To a cold (-30° C.) solution of 2,6-dimethoxycinnamic acid methyl ester (5.2 g, 23.4 mmol, prepared as described above), in chloroform (250 ml), was added boron tribromide (80 ml of a 1M solution in methylene chloride). The mixture was allowed to stir under anhydrous conditions was poured into saturated aqueous sodium hydrogen carbonate solution (400 ml). [Caution Frothing] The organic phase was diluted with ethyl acetate (250 ml), the mixture was transferred to a separating funnel and extracted thoroughly. The organic phase was isolated, dried (MgSo4) and evaporated in vacuo to give a dark red oil which did not crystallize. The oil was purified further by chromatography on silica gel to give 5-hydroxycoumarin (3.4 g, 89%), as a pale-yellow crystalline powder. M.p. 226°-229 ° C. (Das Gupta et al. J. Chem. Soc. (C), 29, 1969 give m.p. 224°-225° C.) 1H NMR (DMSO-d6): 8.11 (dd, J=9,6,0.6Hz, 1H), 7.40 (t, J=8.4Hz, 1H), 6.78 (m, 2H), 6.34 (d, J=9.6Hz, 1H).

Workup

  1. customthe mixture was transferred to a separating funnel
  2. extractionextracted thoroughly
  3. customThe organic phase was isolated
  4. customdried (MgSo4)
  5. customevaporated in vacuo
  6. customto give a dark red oil which
  7. customdid not crystallize
  8. customThe oil was purified further by chromatography on silica gel

Sources & evidence

ORD record
ord-feb08e9c917441159aff790c22ad0ac8
Source dataset
uspto-grants-1995_09
Patent number
US05449602

Reaction notes

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