Dimethyl Sulfate → 2,4-Dibromo-3,5-dimethylthiophene

HRID 1290240Notes

Reaction equation

HRID 1290240 reaction equation
[Br:1][C:2]1[S:3][C:4](Br)=[C:5]([Br:8])[C:6]=1[CH3:7].[Li][CH2:11]CCC.S(OC)(OC)(=O)=O>C(OCC)C>[Br:1][C:2]1[S:3][C:4]([CH3:11])=[C:5]([Br:8])[C:6]=1[CH3:7]

Participants

5

Reactant 3

HCID 6497Dimethyl SulfateHCID 30178012,3,5-Tribromo-4-methylthiopheneHCID 178418339Butyllithium

Product 1

HCID 105880762,4-Dibromo-3,5-dimethylthiopheneYield 55%

Reagents, catalysts & solvents 1

HCID 3283Diethyl EtherSolvent2×

Procedure

A solution of 2,4,5-tribromo-3-methylthiophene (50.2 g, 0.15 mol; Gronowitz, S.; Moses, P. Hakansson Arkiv. f. Kemi. 1960, 14, 267) in 400 mL of diethyl ether was cooled to -78° C., and a solution of nBuLi (100 mL, 1.6M) was added dropwise. The starting material precipitated out of solution, but when n-BuLi added, the reaction mixture became stirrable again. When the addition was complete, the reaction mixture was stirred for 20 min, and then a solution of dimethyl sulfate (75.7 g, 0.600 mol) in 200 mL of diethyl ether which was cooled to -50° C. was added by cannulation. When addition was complete, the reaction mixture was allowed to warm to ambient temperature and was stirred overnight. The reaction was quenched with 100 mL of 6N NaOH solution and stirred for 2h. The mixture was transferred to a separatory funnel, and the aqueous layer was separated and extracted with additional ether. The organic layers were combined, washed with water and brine and dried (MgSO4). The suspension was filtered and concentrated to give an oil. Vacuum distillation provided 22.1 g (55%) of 2,4-dibromo-3,5-dimethylthiophene, A8, b.p. 71°-72° C. @ 0.4 mmHg. The 1H NMR in CDCl3 supported the assigned structure. ##STR58##

Workup

  1. customThe starting material precipitated out of solution, but when n-BuLi
  2. additionadded
  3. additionWhen the addition
  4. additionwas added by cannulation
  5. additionWhen addition
  6. stirringwas stirred overnight
  7. customThe reaction was quenched with 100 mL of 6N NaOH solution
  8. stirringstirred for 2h
  9. customThe mixture was transferred to a separatory funnel
  10. customthe aqueous layer was separated
  11. extractionextracted with additional ether
  12. washwashed with water and brine
  13. dry with materialdried (MgSO4)
  14. filtrationThe suspension was filtered
  15. concentrationconcentrated
  16. customto give an oil
  17. distillationVacuum distillation

Sources & evidence

ORD record
ord-52731ac83f494f57853654b48a959781
Source dataset
uspto-grants-1998_05
Patent number
US05750720

Reaction notes

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