Reaction #70957

Reaction equation

1,2-bis(2,5-dimethyl-3-thienyl)ethanedione

benzene

Potassium t-butoxide

benzene

→

25

Yield 25.0%

3,4-bis(2,5-dimethyl-3-thienyl)cyclohexadiene

Yield 25.0%

Conditions

Workup

1. 1
   TemperatureThe resulting orange solution was heated
2. 2
   Temperatureto reflux
3. 3
   workup.STIRRINGThe reaction mixture was stirred
4. 4
   Temperatureat reflux for 20 min, at which point the heating mantle
5. 5
   Otherwas removed
6. 6
   Temperatureto cool to room temperature
7. 7
   OtherThe reaction was quenched by the addition of water (50 mL)
8. 8
   Extractionextracted with Et2O (3×50 mL)
9. 9
   Washwashed with brine
10. 10
    Dryingdried over MgSO4
11. 11
    Filtrationfiltered
12. 12
    OtherThe solvent was removed under reduced pressure
13. 13
    Otherthe residue was purified by column chromatography through silica (1:9 EtOAc:hexanes)

Procedure

Potassium t-butoxide (163 mg, 1.45 mmol) was added to a suspension of 1,4-butanebis(triphenylphosphonium)dibromide (537 mg, 0.725 mmol) in benzene (50 mL). The reaction was stirred for 45 min at room temperature. The resulting orange solution was heated to reflux and treated drop-wise with a solution of 1,2-bis(2,5-dimethyl-3-thienyl)ethanedione 23 (202 mg, 0.72 mmol) in benzene (25 mL). The reaction mixture was stirred at reflux for 20 min, at which point the heating mantle was removed and the reaction was allowed to cool to room temperature. The reaction was quenched by the addition of water (50 mL) and extracted with Et2O (3×50 mL). The organic extracts were combined, washed with brine, dried over MgSO4 and filtered. The solvent was removed under reduced pressure and the residue was purified by column chromatography through silica (1:9 EtOAc:hexanes) to yield 55 mg (25%) of 25 as a white solid. Mp=55-57° C. 1H NMR (CDCl3): δ=6.13 (s, 2H), 5.88 (m, 2H), 2.26 (m, 10H), 2.14 (s, 6H); 13C NMR (CDCl3) δ=137.8, 134.4, 133.9, 131.6, 127.4, 126.7, 22.7, 15.1, 14.0. MS (EI): m/z=300 (M+).

Source