Reaction #48897

Reaction equation

ether

3-methyl-2-((1E,3E)-4-phenylamino-buta-1,3-dienyl)-5-sulfo-1,3-bis-(3-sulfo-propyl)-3H-indolium disodium salt

3-(3-Carboxypropyl)-2,3-dimethyl-5-sulfonato-1-(3-sulfopropyl)-3H-indolium sodium salt

pyridine

→

2-{(1E,3E)-5-[3-(3-carboxy-propyl)-3-methyl-5-sulfo-1-(3-sulfo-propyl)-1,3-dihydro-indole-(2E)-ylidene]-penta-1,3-dienyl}-3-methyl-5-sulfo-1,3-bis-(3-sulfo-propyl)-3 H-indolium tetrasodium salt

Solvents

acetic acid

acetic anhydride

Conditions

Workup

1. 1
   Temperatureunder reflux for 15 min
2. 2
   workup.ADDITIONThe obtained precipitate (mixture of the diastereomers
3. 3
   Extractionand OB-5.5b) was extracted by suction
4. 4
   Washwashed with ether
5. 5
   Otherdried

Procedure

642 mg (1 mmol) 3-methyl-2-((1E,3E)-4-phenylamino-buta-1,3-dienyl)-5-sulfo-1,3-bis-(3-sulfo-propyl)-3H-indolium disodium salt and 483 mg (1 mmol) 3-(3-Carboxypropyl)-2,3-dimethyl-5-sulfonato-1-(3-sulfopropyl)-3H-indolium sodium salt were dissolved in a mixture of 10 ml acetic acid and 10 ml acetic anhydride. Five ml pyridine was added. The solution was stirred under reflux for 15 min. Twenty ml ether was added after cooling to room temperature. The obtained precipitate (mixture of the diastereomers OB-5.5a and OB-5.5b) was extracted by suction, washed with ether, and dried.

Source