Methanol → 3-Bromo-4-methylthiophene

HRID 2372659Notes

Reaction equation

HRID 2372659 reaction equation
CO.[CH3:3][C:4]1[C:8]([Br:9])=[C:7]([Br:10])[S:6][C:5]=1Br.BrCC1C=C(Br)SC=1Br.BrC1SC=C(Br)C=1C>[Br-].C([N+](CC)(CC)CC)C.[Cl-].[Zn+2].[Cl-].C(Cl)Cl>[Br:9][C:8]1[C:4]([CH3:3])=[CH:5][S:6][CH:7]=1.[Br:10][C:7]1[S:6][CH:5]=[C:4]([CH3:3])[C:8]=1[Br:9]

Participants

9

Reactant 4

HCID 887MethanolHCID 30178012,3,5-Tribromo-4-methylthiopheneHCID 12245922Thiophene, 2,5-dibromo-3-(bromomethyl)-HCID 148351682,4-Dibromo-3-methylthiophene

Product 2

HCID 27349353-Bromo-4-methylthiopheneYield 89.9%HCID 144308112,3-Dibromo-4-methylthiopheneYield 1.2%

Reagents, catalysts & solvents 3

HCID 6285Tetraethylammonium BromideCatalystHCID 3007855ZincchlorideCatalystHCID 6344DichloromethaneSolvent

Procedure

A catholyte of 2 l of methanol, 500 ml of methylene chloride, 1 g of zinc chloride, 5 g of tetraethylammonium bromide and 159 g of a mixture of 3-methyl-2,4,5-tribromothiophene (95%) and 3-bromomethyl-2,5-dibromothiophene (5%) was electrolysed in the electrolysis cell 1 at a current density of 100 mA/cm2, a voltage of 7 to 8 V and a temperature of 28° to 38° C. The current consumption was 53 Ah. During the electrolysis, the pH of the catholyte was kept at a value between 5 and 7 by addition of a total of 150 g of sodium hydroxide in portions. After addition of 2 l of water to the catholyte, phase separation, extraction with CF2Cl--CFCl2 and removal of the solvent by distillation, 73.67 g of 3-bromo-4-methylthiophene (yield: 89.9%), 1.47 g of 2,4-dibromo-3-methylthiophene and 2,3-dibromo-4-methylthiophene (yield: 1.2%) and 4.16 g of 3-methylthiophene (yield: 8.9%) were obtained.

Workup

  1. customa temperature of 28° to 38° C
  2. customThe current consumption
  3. additionDuring the electrolysis, the pH of the catholyte was kept at a value between 5 and 7 by addition of a total of 150 g of sodium hydroxide in portions
  4. additionAfter addition of 2 l of water
  5. customto the catholyte, phase separation, extraction
  6. customwith CF2Cl--CFCl2 and removal of the solvent

Sources & evidence

ORD record
ord-6a27bf9d054a42328ca8ba69c9681617
Source dataset
uspto-grants-1992_03
Patent number
US05100520

Reaction notes

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