| Coupler is an important research content in the photographic materials. A method for the synthesis of a cyan coupler is studied in this paper, which helps to the basis of the production of the coupler and the development of the coupler synthesis.On the basis of literatures, a route for the synthesis of the cyan coupler was designed: N-(4-nitro-5-chloro-2-hydroxyphenyl)-3,4-dichloro benzamide (4) was synthesized by amidation between 2-amino-4-chloro-5-nitrophenol(2) and 3,4-dichloro benzoyl chloride(3); N-(4-amino-5-chloro-2-hydroxyphenyl)-3,4-dichloro ben-zamide(5) was got by Au-Pd/C selective catalytic hydrogenation of (4); 2-[(4-dodecyloxy phenyl)sulfonyl] ethyl butyrate(9) was got by the oxidation of 2-[(4-dodecyloxy phenyl)thio] ethyl butyrate(8), which was synthesized by 4-Dodecyloxythiophenol(7) and 2-bromoethyl butyrate(6). At last, the amidation between ester group of (9) and the amino group of (5) gave the title coupler 3,4-dichloro-N-[5-chloro-4-[[2-[[4-(dodecyloxy) phenyl]sulfonyl]-l-oxobutyl] ami-no]-2-hydroxyphenyl]-benzamide(l). And the related unit reactions were optimized and improved.N-(4-nitro-5-chloro-2-hydroxyphenyl)-3,4-dichloro benzamide (4) was synthesized by amidation between 2-amino-4-chloro-5-nitrophenol(2) and 3,4-dichloro benzoyl chloride(3), for which the reaction conditions were: ethyl acetate as the solvent, the mole ratio of the raw material was 1:1, reacted at the reflux temperature. The yield of the product (4) was 99.2%.In the reaction of selective catalytic hydrogenation of (4), in which N-(4-amino-5-chloro-2-hydroxyphenyl)-3,4-dichloro benzamide(5) as the product, the Au-Pd/C catalyst was made to avoid the by-reaction of hydrodechlorination, and the influences were studied. The best conditions were: DMF as the solvent, the catalyst was of 5% weight of the raw material needed, the mass ratio of Pd to Au was 1 in the catalyst, the reaction pressure was 1.5MPa, the reaction temperature was 80℃, andthe catalyst could be used for 5 times without obvious drop of the performance. The yield of the product (5) was 91.8%.In the synthesis of 2-[(4-dodecyloxy phenyl)thio] ethyl butyrate(8), the optimized conditions were: ethanol as the solvent, sodium ethoxide was added to promote the reaction, the ethanol solution of 4-Dodecyloxythiophenol(7) was added under the room temperature, the reaction temperature was maintained between 60-70℃, and the raw product was got after washing, dryness and evaporating the solvent when the reaction was finished. The raw product was used in next step without purification.2-[(4-dodecyloxy phenyl)sulfonyl] ethyl butyrate(9) was got by the oxidation of (8), and the optimized conditions were: acetic acid as the solvent, sodium tungstate as the catalyst, 27% hydrogen peroxide was added, and the temperature was maintained at 50℃ during the addition, reaction was carried out at reflux temperature which was about 110℃. The excessive hydrogen peroxide was eliminated by sodium sulfite. After extraction by ethyl acetate the solvent was evaporated. The product was got by re-crystallization with n-hexane, the yield of which was 89.1%.Finally the cyan coupler 3,4-dichloro-N-[5-chloro-4-[[2-[[4-(dodecyloxy) phenyl] sulfonyl]-1 -oxobutyl] amino] -2-hydroxyphenyl] -benzamide(1) was synthesized by 2-[(4-dodecyloxy phenyl)sulfonyl] ethyl butyrate(9) and N-(4-amino-5-chloro-2-hydroxyphenyl)-3,4-dichloro benzamide(5). The reactive distillation was used to separate the ethanol from the reaction system to promote the reaction. The solvent was evaporated after the reaction finished, and ethyl acetate and petroleum ether whose mass ratio was 1 were used in recrystallization. The yield of the product was 77.7%, and the melting point matched the references of 163.5-164.2℃. All the products and intermediates above are confirmed by melting points and NMR.The technique studied in this paper has some advantages: the conditions of each step are mild, the yield of the product is steady and the reactions are easy to be carried out.
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