Synthesis
The general procedure for the synthesis of 3,4-diaminodiphenyl ether from 2-nitro-5-phenoxyaniline was as follows: 1.1 g (4.9 mmol) of 2-nitro-5-phenoxyaniline synthesized in the previous step was dissolved in 10 mL of ethanol and 0.03 g (0.24 mmol) of palladium-carbon catalyst was added. Three gas substitutions were carried out under argon protection, followed by three more substitutions under hydrogen atmosphere. The reaction was carried out at room temperature for about 3 hours. Upon completion of the reaction, ethanol was removed by rotary evaporation and 20 mL of water was added. Multiple extractions were carried out with ethyl acetate and the organic phases were combined, dried over anhydrous sodium sulfate and the solvent was removed by rotary evaporation. Purification by column chromatography afforded 0.74 g of the target product 3,4-diaminodiphenyl ether in 75.4% yield.
References
[1] Journal of Heterocyclic Chemistry, 1997, vol. 34, # 3, p. 745 - 748
[2] Patent: US5972968, 1999, A
[3] Indian Journal of Heterocyclic Chemistry, 2010, vol. 19, # 4, p. 345 - 348
[4] Bioorganic and Medicinal Chemistry Letters, 2014, vol. 24, # 17, p. 4250 - 4253
[5] Patent: CN104876878, 2018, B. Location in patent: Paragraph 0076-0078
