Water → 1,3-Diethyl-5-{bis[(1,3-diethyl-1H-imidazo[4,5-b]quinoxalin-2-(3H)-ylidene)methyl]methylene}-2-thiobarbituric acid

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A mixture of 1,3-diethyl-2-[(1,3-diethyl-1H-imidazo[4,5-b]quinoxalin-2-(3H)-ylidene)-1-propynyl]imidazo[4,5-b]quinoxalinium perchlorate) 0.33 g, 0.0005 mol) of Example 1, 1,3-diethyl-2-thiobarbituric acid (0.11 g, 0.0005 mol) and triethylamine (0.10 g, 0.001 mol) in dimethylformamide (5 ml), is heated at reflux for 30 seconds. After cooling the solution is diluted to 20 ml. with water. The dye is collected and washed with water. After recrystallization from acetonitrile, the yield of purified dye is 0.27 g (79%) - mp. indistinct.

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