Triethylamine → 1,3-Diethyl-5-[5,5-dimethyl-1-(1-pyrrolidinyl)-1-cyclohexen-3-ylidene]-2-thiobarbituric acid

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Reaction Steps

N-(3-Chloro-5,5-dimethylcyclohex-2-en-1-ylidene)-pyrrolidinium perchlorate (3.1 g., 0.01 mol.), 1,3-diethyl-2-thiobarbituric acid (2.0 g., 0.091 mol.) and triethylamine (3.1 ml.) are dissolved in ethanol (15 ml.) and heated at reflux for 10 minutes. After chilling, the crude dye is collected on a filter, rinsed with ethanol and dried. After one recrystallization from methanol, the yield of purified dye is 2.3 g. (64%), m.p. 226°-227°C. This dye is an excellent spectral sensitizer for photographic silver halide emulsions as shown in Table 2 hereinafter.

Provenance & Evidence