Boron tribromide → 2,2-dimethyl-3,4-dihydro-2H-1-benzopyran-7-ol

HRID 856943

Reaction equation

HRID 856943 reaction equation
C[O:2][C:3]1[CH:12]=[C:11]2[C:6]([CH2:7][CH2:8][C:9]([CH3:14])([CH3:13])[O:10]2)=[CH:5][CH:4]=1.B(Br)(Br)Br.C([O-])(O)=O.[Na+]>ClCCl>[CH3:13][C:9]1([CH3:14])[CH2:8][CH2:7][C:6]2[C:11](=[CH:12][C:3]([OH:2])=[CH:4][CH:5]=2)[O:10]1

Participants

5

Reactant 3

HCID 25134Boron tribromideHCID 516892Sodium BicarbonateHCID 108563167-Methoxy-2,2-dimethyl-chroman

Product 1

HCID 110412812,2-dimethyl-3,4-dihydro-2H-1-benzopyran-7-olYield 42%

Reagents, catalysts & solvents 1

HCID 6344DichloromethaneSolvent

Procedure

To a stirred solution of 7-Methoxy-2,2-dimethyl-chroman (4.55 g, 23.7 mmol, from step 1) in anhydrous dichloromethane (50 mL) was added 1M BBr3 (72.86 mL, 47.4 mmol, 2.0 eq) via cannula over 10 min. The resulting dark brown solution was stirred at rt for 17 h. Saturated solution of NaHCO3 (50 mL) was added and extracted with CH2Cl2 (3×50 mL. The combined organic layers were dried over Na2SO4, filtered and evaporated. The residue was purified on silica gel (flash column chromatography) eluting with 5% ethyl acetate-hexane followed by 20% ethyl acetate-hexane to provide the desired product as white solid (1.76 g, 42%). 1H-NMR (CD3CN) δ 6.89 (d, J=8.5 Hz, 1H), 6.68 (broad, s, 1H, OH), 6.31 (dd, J=2.4, 8.5 Hz, 1H), 6.15 (d, J=2.4 Hz, 1H), 2.69 (t, 2H), 1.79 (t, 2H), 1.31 (s, 6H). MS LC-MS (MH+=179).

Workup

  1. extractionextracted with CH2Cl2 (3×50 mL
  2. dry with materialThe combined organic layers were dried over Na2SO4
  3. filtrationfiltered
  4. customevaporated
  5. customThe residue was purified on silica gel (flash column chromatography)
  6. washeluting with 5% ethyl acetate-hexane

Sources & evidence

ORD record
ord-22d881df84794970a63c9898587c5e27
Source dataset
uspto-grants-2006_12
Patent number
US07144885B2

Linked notes

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