Process for the preparation of 1-amino-2-ethoxy-naphthalene-6-sulphonic acid

US4341719A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Rolf Putter
• Theodor Pfister · Monheim, DE
• Manfred Niese · Leverkusen, DE
• Peter Wenzl · Cologne, DE

Key dates

• Filing date: Feb 26, 1981
• Grant date: Jul 27, 1982
• Expiry date: Feb 26, 2001

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C309/00
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

A process for the preparation of 1-amino-2-ethoxy-naphthalene-6-sulphonic acid from 2-hydroxy-naphthalene-6-sulphonic acid which comprises: PA0 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.degree. to 20.degree. C.; PA0 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.degree. to 120.degree. C., and treating the thus-obtained reaction mixture with aqueous alkali metal hydroxide in the presence of iron oxide; PA0 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.degree. to 100.degree. C.; PA0 D. contacting the product of step C with an ethylating agent in the presence of an acid binding agent in an aqueous-org…