118-28-5Relevant articles and documents
Process for the preparation of 1-amino-2-ethoxy-naphthalene-6-sulphonic acid
-
, (2008/06/13)
A process for the preparation of 1-amino-2-ethoxy-naphthalene-6-sulphonic acid from 2-hydroxy-naphthalene-6-sulphonic acid which comprises: A. contacting 2-hydroxy-naphthalene-6-sulphonic acid with at least an equimolar amount of an alkali metal nitrite in aqueous solution or suspension in the presence of hydrochloric acid, solution or suspension having a pH in the range of 2 to 5 and being at a temperature of 0° to 20° C.; B. reducing the reaction product of step A in an aqueous suspension by contacting the same with excess iron in the presence of at least an equivalent amount of iron-II ions, relative to the reaction product obtained according to step A, in the presence of a mineral acid at a temperature from 50° to 120° C., and treating the thus-obtained reaction mixture with aqueous alkali metal hydroxide in the presence of iron oxide; C. contacting the product of step B with excess acetic anhydride in an aqueous solution or suspension at a pH in the range of 3 to 10 at a temperature from 0° to 100° C.; D. contacting the product of step C with an ethylating agent in the presence of an acid binding agent in an aqueous-organic solvent or diluent in a pH range from 8 to 14 at a temperature from 20° to 150° C.; and E. deacetylating the product of step D by contacting the same at reflux with an aqueous alkali metal hydroxide.