Iodine → (2,5-Dimethylphenyl)boronic acid

HRID 430878Notes

Reaction equation

HRID 430878 reaction equation
[Mg].II.Br[C:5]1[CH:10]=[C:9]([CH3:11])[CH:8]=[CH:7][C:6]=1[CH3:12].[B:13](OC)([O:16]C)[O:14]C.S(=O)(=O)(O)O>BrC1C=C(C)C=CC=1C.C1COCC1>[CH3:12][C:6]1[CH:7]=[CH:8][C:9]([CH3:11])=[CH:10][C:5]=1[B:13]([OH:16])[OH:14]

Participants

8

Reactant 5

HCID 807IodineHCID 1118Sulfuric AcidHCID 8470Trimethyl borateHCID 11121Benzene, 2-bromo-1,4-dimethyl-HCID 5462224Magnesium

Product 1

HCID 2734347(2,5-Dimethylphenyl)boronic acidYield 64%

Reagents, catalysts & solvents 2

HCID 11121Benzene, 2-bromo-1,4-dimethyl-CatalystHCID 8028TetrahydrofuranSolvent2×

Procedure

Magnesium turnings (13.3 g; 0.55 mol) are introduced into a baked-out, argon-blanketed apparatus, covered with about 30 ml of THF and a few crystals of iodine are added. Without stirring, a few drops of bromo-p-xylene (cf. Example A1 a)) were subsequently added to the solution. The Grignard reaction began very quickly and the remaining bromo-p-xylene (total amount: 92.5 g; about 70 ml; 0.5 mol) was subsequently added dropwise while stirring. The mixture was refluxed for 4 hours and then cooled. The Grignard solution was then transferred in a countercurrent of protective gas into a 500 ml dropping funnel and added dropwise to a solution of trimethyl borate (62.4 g; 67 ml; 0.6 mol) in 350 ml of THF while stirring at −70° C. (time: about 1 hour). A precipitate was formed during this addition. The reaction mixture was allowed to warm to RT overnight and was then introduced while stirring into a mixture of 700 g of ice and 20 ml of concentrated sulfuric acid. The organic phase was separated off, the aqueous phase was extracted three times with chloroform and the combined organic phases were evaporated. The crude product was recrystallized from chloroform/hexane. This gave a colorless microcrystalline powder 47.71 g (64%).

Workup

  1. additionExample A1 a)) were subsequently added to the solution
  2. customThe Grignard reaction
  3. stirringwhile stirring
  4. temperatureThe mixture was refluxed for 4 hours
  5. temperaturecooled
  6. stirringwhile stirring at −70° C. (time: about 1 hour)
  7. customA precipitate was formed during this addition
  8. additionwas then introduced
  9. customThe organic phase was separated off
  10. extractionthe aqueous phase was extracted three times with chloroform
  11. customthe combined organic phases were evaporated
  12. customThe crude product was recrystallized from chloroform/hexane

Sources & evidence

ORD record
ord-f5208d390c194cfebee40fe433d2f058
Source dataset
uspto-grants-2001_11
Patent number
US06323373B1

Reaction notes

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