Trimethyl orthoformate → 6-Bromo-5-chlorobenzoxazole

HRID 874604Notes

Reaction equation

HRID 874604 reaction equation
[NH2:1][C:2]1[CH:7]=[C:6]([Cl:8])[C:5]([Br:9])=[CH:4][C:3]=1[OH:10].[Yb+3].F[C:13](F)(F)S([O-])(=O)=O.FC(F)(F)S([O-])(=O)=O.FC(F)(F)S([O-])(=O)=O.C(OC)(OC)OC>CCO.CC(=O)OCC.CCCCCC>[Br:9][C:5]1[C:6]([Cl:8])=[CH:7][C:2]2[N:1]=[CH:13][O:10][C:3]=2[CH:4]=1

Participants

7

Reactant 3

HCID 9005Trimethyl orthoformateHCID 2733225Ytterbium triflateHCID 584871002-Amino-5-bromo-4-chlorophenol

Product 1

HCID 584872776-Bromo-5-chlorobenzoxazoleYield 6,559.2%

Reagents, catalysts & solvents 3

HCID 702EthanolSolventHCID 8058HexaneSolventHCID 8857Ethyl AcetateSolvent2×

Conditions

Temperature
90 °C

Procedure

A mixture of 2-amino-5-bromo-4-chlorophenol (29) (865 mg, 3.89 mmol), trifluoromethanesulfonic acid Ytterbium (III) salt (24 mg, 1% mol) and trimethyl orthoformate (511 μl, 1.2 eq.) in 2 ml EtOH was heated at 90° C. for 2 h. After cooling down to r.t., the reaction mixture was taken up in EA, washed with aq. NaHCO3 and brine, dried over Na2SO4, concentrated to dryness. The resulting brown solid was dissolved in DCM and subjected to silica gel column purification using 0-100% B (A: hexane; B: 50% EA in hexane) to furnish 590 mg 30 as yellow solid (yield: 65.2%).

Workup

  1. temperatureAfter cooling down to r.t.
  2. washwashed with aq. NaHCO3 and brine
  3. dry with materialdried over Na2SO4
  4. concentrationconcentrated to dryness
  5. dissolutionThe resulting brown solid was dissolved in DCM
  6. customsubjected to silica gel column purification

Sources & evidence

ORD record
ord-2c55f35bb8d9410eabf22e12ba737ad9
Source dataset
uspto-grants-2015_03
Patent number
US08980629B2

Reaction notes

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