1,2-Dibromoethane → 4-Formylphenylboronic Acid

HRID 1781781Notes

Reaction equation

HRID 1781781 reaction equation
[Mg].Br[CH2:3][CH2:4]Br.COCCO[AlH2-]OCC[O:15][CH3:16].[Na+].[B:18](OCCCC)([O:24]CCCC)[O:19]CCCC.[CH2:34]1[CH2:38]O[CH2:36][CH2:35]1>>[CH:16]([C:4]1[CH:3]=[CH:38][C:34]([B:18]([OH:24])[OH:19])=[CH:35][CH:36]=1)=[O:15]

Participants

6

Reactant 5

HCID 78391,2-DibromoethaneHCID 8028Tetrahydrofuran4×HCID 12712Tributyl borateHCID 5462224MagnesiumHCID 16684438Red-Al

Product 1

HCID 5910734-Formylphenylboronic Acid

Procedure

Under an argon atmosphere, 3.65 g of magnesium turnings are covered with 15 ml of anhydrous THF and treated with 0.5 ml of 1,2-dibromoethane. Gentle warming leads to a vigorous reaction. After the reaction has subsided, the solvent is pipetted off with a pipette, treated with 40 ml of anhydrous THF and 1/3 of a solution of 32 g of the product 1a) in 30 ml of anhydrous THF are added. The reaction is started with Red-Al and by warming. The remainder of the product from 1a) is then added dropwise within the course of 35 min. After dropwise addition is complete, the mixture is boiled under reflux for a further 1 h. The Grignard product is then added dropwise to a solution, cooled to -68° C., of 33.5 ml of tributyl borate under an argon atmosphere in 50 ml of THF. After 30 min, the cooling is removed. The mixture is then stirred at RT for 1 h. It is then concentrated, the honey-colored oil is taken up in 100 ml of ether and 80 ml of Ace-cold H2SO4 (1M) are added. The ether phase is separated off and extracted twice more with 50 ml of ether, concentrated and 30% strength (6N) KOH is added until an alkaline reaction (pH 14) occurs. 70 ml of H2O are added and the butanol is removed azeotropically at 35°-40° C. in a high vacuum. This process is repeated again with 50 ml of H2O. The residue is rendered acidic with 1M H2SO4 (pH 1) and boiled for 30 min. The title compound is obtained as a pale yellow solid by filtration. m.p.=255°-260° C.

Workup

  1. temperatureGentle warming
  2. customleads to a vigorous reaction
  3. additionare added
  4. temperatureby warming
  5. additionAfter dropwise addition
  6. temperatureunder reflux for a further 1 h
  7. additionThe Grignard product is then added dropwise to a solution
  8. customthe cooling is removed
  9. concentrationIt is then concentrated
  10. addition80 ml of Ace-cold H2SO4 (1M) are added
  11. customThe ether phase is separated off
  12. extractionextracted twice more with 50 ml of ether
  13. concentrationconcentrated
  14. addition30% strength (6N) KOH is added until an alkaline reaction (pH 14)
  15. addition70 ml of H2O are added
  16. customthe butanol is removed azeotropically at 35°-40° C. in a high vacuum
  17. waitboiled for 30 min

Sources & evidence

ORD record
ord-06766ac25d6b48cc939c274d6b783b58
Source dataset
uspto-grants-1997_05
Patent number
US05633400

Reaction notes

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