Synthesis Of 2,5-Diamino-benzeneethanol

2,5-Diamino-benzeneethanol and its salts, usually used as a kind of oxidative hair dye, are also employed in dye, pigment, polymer and pesticide.In this article, o-aminobenzeneethanol, used as starting material, took a cyclization with urea in solution toluene. White solid 4,5-dihydrobenzo[d][1,3]oxazepin-2(lH)-one was obtained and took a further nitration at low temperature in solution sulfuric acid. After hydrolysis, yellow solid 2-amino-5-nitro-benzeneethanol was obtained and finally hydrogenation was employed to get the product 2,5-diamino-benzeneethanol.After browsing related articles and comparing with other synthetic routes of 2,5-diamino-benzeneethanol, an improved technical route was developed.First, o-aminobenzeneethanol and urea, toluene and sulfuric acid were used as starting materials, solvent and catalyst, respectively. Under the protection of nitrogen, white solid 4,5-dihydrobenzo[d][1,3]oxazepin-2(lH)-one was obtained after stirring 15 hours with a yield of 75%.In nitration, fuming nitric acid was dropped below 0℃ in solution sulfuric acid. After dropping and stirring 1 hour, nitro product 4,5-dihydrobenzo[d][1,3]oxazepin-2(lH)-one was obtained.The product was directly taken hydrolysis in acid at 80 ℃ without purification. After 8 hours stirring, the solution was cooled below room temperature and sodium hydroxide was used to adjust pH to 8~9. The yellow product 2-amino-5-nitro-benzeneethanol was obtained with a yield of 60%.In hydrogenation, methanol and Pd/C were used as solvent and catalyst. After hydrogenation and salifying at 50℃, white product 2,5-diamino-benzeneethanol was obtained with a yield of 92%.From the investigation, an economical and practical technical route of synthesizing 2,5-diamino-benzeneethanol was developed, which had a steady yield. Since the materials, expect for o-aminobenzeneethanol, are inexpensive and easily available, the production cost is considerably saved and the total yield is 41.4%, which means apotential industrial application.