[CH3:1][O:2]C1C=CC=C(OC)C=1.COC1C=CC2C(=CC(OC)=CC=2)C=1.COC1C=CC2C(=CC3C(C=2)=CC=CC=3OC)C=1.N.[Na].[NH:45]1[C:52](=[O:53])[CH2:51][C:49](=[O:50])[NH:48][C:46]1=[S:47]>C(O)C>[CH3:1][O:2][CH:51]1[C:49](=[O:50])[NH:48][C:46](=[S:47])[NH:45][C:52]1=[O:53]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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