Process for the preparation of 3-hydroxy-N-benzimidazolon-5-yl-2-naphthamide in the high purity required of azo pigments

US5756757A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Michael Meier · Frankfurt am Main, DE
• Heinrich Volk · Beerfelden, DE
• Rudolf Neeb · Offenbach am Main, DE

Key dates

• Filing date: Nov 16, 1995
• Grant date: May 26, 1998
• Expiry date: Nov 16, 2015

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07D235/26
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The invention relates to a process for the preparation of 3-hydroxy-N-benzimidazolon-5-yl-2-naphthamide, which comprises reacting 5-aminobenzimidazolone and sodium carbonate in N-methylpyrrolidone with a solution of 3-hydroxy-2-naphthoyl chloride in xylene or toluene, filtering, washing with xylene or toluene, introducing the filter cake into water to which sodium carbonate has been added and steam-distilling, filtering off the residue with suction, washing and drying.