N,N'-Diphenylformamidine → 3-methyl-2-((E)-2-phenylamino-vinyl)-1,3-bis-(3-sulfo-propyl)-3H-indolium sodium salt

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Reaction Steps

0.822 g (2 mmol) 2,3-dimethyl-1,3-bis-(3-sulfo-propyl)-3H-indolium sodium salt 7 and 0.49 g (2.5 mmol) N,N′-diphenyl-formamidine are dissolved in 20 ml methanol and stirred for about four hours under reflux. The solvent is removed in vacuum after cooling to room temperature. The residue is washed carefully with ethyl acetate. A dark yellow solid is obtained which is processed without further purification.

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