Reaction #75461

Reaction equation

dihydrothiophene

EDOT

sodium hydroxide

2,5-dicarbethoxy-3,4-ethylenedioxythiophene

1,2-dibromohexane

1,2-dibromohexadecane

1,2-dibromoethane

K2CO3

EDOT

→

2,5-dicarboxy-3,4-ethylenedioxythiophene

Solvents

water

DMF

Conditions

Workup

1. 1
   workup.ADDITIONadded slowly dropwise
2. 2
   FiltrationAfter filtration
3. 3
   Washthe precipitate is washed with water
4. 4
   Otherair-dried
5. 5
   Otherto give 2,5-dicarbethoxy-3,4-dihydroxythiophene (Z)
6. 6
   OtherTo prepare the
7. 7
   Filtrationthe resulting insoluble material is collected by filtration
8. 8
   Otherrecrystallized from methanol

Procedure

The salt either 5 or 6 is dissolved in water and acidified with 1 Molar HCI added slowly dropwise with constant stirring until the solution becomes acidic. Immediately following, thick white precipitate falls out. After filtration, the precipitate is washed with water and air-dried to give 2,5-dicarbethoxy-3,4-dihydroxythiophene (Z). The salt either (5, 2.5 grams) or 6 can be alkylated directly or the dihydrothiophene derivative (7) can be suspended in the appropriate 1,2-dihaloalkane or substituted 1,2-dihaloalkane and refluxed for 24 hours in the presence of anhydrous K2CO3 in anhydrous DMF. To prepare EDOT, either 1,2-dicholorethane (commercially available from Aldrich) or 1,2-dibromoethane (commercially from Aldrich) is used. To prepare the various substituted EDOT derivatives the appropriate 1,2-dibromoalkane is used, such as 1-dibromodecane, 1,2-dibromohexadecane (prepared from 1-hexadecene and bromine), 1,2-dibromohexane, other reported 1,2-dibromoalkane derivatives, and the like. The resulting 2,5-dicarbethoxy-3,4-ethylenedioxythiophene or 2,5-dicarbethoxy-3,4-alkylenedioxythiophene is refluxed in base, for example 10 percent aqueous sodium hydroxide solution for 1 to 2 hours, and the resulting insoluble material is collected by filtration. This material is acidified with 1 Normal HCl and recrystallized from methanol to produce either 2,5-dicarboxy-3,4-ethylenedioxythiophene or the corresponding 2,5-dicarboxy-3,4-alkylenedioxythiophene. The final step to reduce the carboxylic acid functional groups to hydrogen to produce the desired monomer is given in the references above.

Source