Pyridine → 2-((E)-3-[3-(carboxy-propyl)-1-ethyl-3-methyl-1,3-dihydro-indol-(2E)-ylidene]-propenyl)-3-methyl-1,3-bis-(3-sulfo-propyl)-3H-indolium sodium salt

Participants

Reaction Steps

500 mg (1 mmol) 1-ethyl-3-methyl-2-((E)-2-phenylamino-vinyl)-5-sulfo-3-(3-sulfo-propyl)-3H-indolium sodium salt 8 and 387 mg (1 mmol) 3-(3-carboxypropyl)-2,3-dimethyl-1-ethyl-3H-indolium iodide salt 3 are dissolved in a mixture of 10 ml acetic acid and 10 ml acetic anhydride. Subsequently, 5 ml of pyridine is added. The solution is stirred under reflux for 15 minutes.

Provenance & Evidence