Reaction #46392

Reaction equation

sulphuric acid

N-(1,1-dioxo-2,3-dihydro-1H-1λ6-benzo[b]thiophen-5-yl)-2-[(E)-hydroxyimino]acetamide

→

desired compound

Yield 52.5%

3,3-dioxo-1,2,3,6-tetrahydro-3λ6-thieno[3,2-e]indole-7,8-dione

Yield 52.5%

Solvents

ethyl acetate

Conditions

Workup

1. 1
   workup.ADDITIONAfter the addition
2. 2
   Temperaturethe reaction mixture was heated to 90° C.
3. 3
   Temperatureto cool to RT
4. 4
   workup.STIRRINGbriefly stirred
5. 5
   OtherAfter separation of the phases
6. 6
   Otherthe solid which formed
7. 7
   Filtrationwas filtered off with suction
8. 8
   Washwashed with diethyl ether
9. 9
   Otherdried in a drying oven at 50° C. overnight

Procedure

6.74 ml (126.38 mmol) of conc. sulphuric acid were introduced into a three-neck round-bottom flask with thermometer and high-efficiency condenser and heated to 70° C. 3.06 g (12.04 mmol) of N-(1,1-dioxo-2,3-dihydro-1H-1λ6-benzo[b]thiophen-5-yl)-2-[(E)-hydroxyimino]acetamide were then added in portions over the course of half an hour, during which the mixture became dark reddish brown in colour. After the addition was complete, the reaction mixture was heated to 90° C. and stirred at this temperature for one hour. For working up, the reaction mixture was allowed to cool to RT and was then added to a mixture of ice-water (110 ml) and ethyl acetate (25 ml) and briefly stirred. After separation of the phases, the solid which formed was filtered off with suction, washed with diethyl ether and dried in a drying oven at 50° C. overnight. 1.50 g of the desired compound were obtained.

Source