Ammonia → 5-Methoxy-2-thioxodihydropyrimidine-4,6(1H,5H)-dione

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Reaction Steps

The first step of synthesis of fused ring bridge, ring locked dyes according to the invention is the Birch reduction of 1,3-dimethoxybenzene, 2,7-dimethoxynaphthalene or 2,8-dimethoxyanthracene using ethanol, liquid ammonia and sodium. The reduced compounds are the starting materials for the synthesis of the dyes, as shown below. ##STR15## The Birch reduction products of 1,3-dimethoxybenzene and of 2,7-dimethoxynaphthalene each react with thiobarbituric acid to form the conjugated methoxy-thiobarbituric acid dyes as shown in FIG. 13. For this reaction, no solvent is used. The reactants were melted at 145° C. for 15 min. Methanol condensing at the walls of the flask showed successful reaction. Purification was carried out by simple filtration over a short column of SiO2 with CH2Cl2. Yields were typically around 60%.

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