Boron tribromide → 4',7-Dihydroxyflavone

HRID 1246574Notes

Reaction equation

HRID 1246574 reaction equation
B(Br)(Br)Br.C[O:6][C:7]1[CH:24]=[CH:23][C:10]([C:11]2[O:12][C:13]3[C:18]([C:19](=[O:21])[CH:20]=2)=[CH:17][CH:16]=[C:15]([OH:22])[CH:14]=3)=[CH:9][CH:8]=1>ClCCl>[OH:6][C:7]1[CH:24]=[CH:23][C:10]([C:11]2[O:12][C:13]3[C:18]([C:19](=[O:21])[CH:20]=2)=[CH:17][CH:16]=[C:15]([OH:22])[CH:14]=3)=[CH:9][CH:8]=1

Participants

4

Reactant 2

HCID 25134Boron tribromide2×HCID 5320693Pratol

Product 1

HCID 52820734',7-Dihydroxyflavone

Reagents, catalysts & solvents 1

HCID 6344DichloromethaneSolvent

Procedure

A boron tribromide solution (1.8 ml, 6 equivalents) is added to a well-stirred solution of 4′-methoxy-7-hydroxyflavone (3 mmol) in dichloromethane (50 ml) at −78° C. under an argon atmosphere. When the addition of the boron tribromide solution is complete, the reaction mixture is stirred at room temperature for 24 hours and introduced into an ice/water mixture (300 ml). The product is filtered off and recrystallised from ethanol/water to give 4′,7-dihydroxyflavone. 1H NMR (300 MHz, d6-DMSO): δ 10.78 (br s, OH), 10.28 (br s, OH), 7.91–6.93 (dm, 4H), 7.87 (d, 1H), 6.98 (d, 1H), 6.72 (s, 1H; 13C NMR (62.90 MHz, d6-DMSO): δ176.19 (s), 162.43 (s), 162.33 (s), 160.58 (s), 157.27 (s), 128.02 (s), 126.36 (s), 121.68 (s), 116.01 (s), 115.78 (s), 114.67 (s), 104.37(s), 102.48 (s); EI-MS (70 eV) m/e (rel. abund.)=254.24 (100). The product is yellowish and exhibits the UV absorption maximum at λ=329 nm with ε=27960 (in 2-propanol) (cf. FIG. 3).

Workup

  1. filtrationThe product is filtered off
  2. customrecrystallised from ethanol/water

Sources & evidence

ORD record
ord-cfd3d56e54be4a4b8d76f40a60543c25
Source dataset
uspto-grants-2006_10
Patent number
US07128900B2

Reaction notes

Loading…