Fuming sulfuric acid → HCID 10355651, compound

Participants

Reaction Steps

The 1-sulfo-6-carboxy-2-aminonaphthalene starting compound has not been disclosed before. It can be prepared according to the present invention by first sulfonating 2-naphthol-6-carboxylic acid in a sulfuric acid/sulfur trioxide mixture (oleum) having a sulfur trioxide content of 0 to 65% by weight at a temperature between 0° C. and 40° C., preferably at 0° to 10° C., to 1-sulfo-6-carboxy-2-naphthol, isolating this compound and then reacting it at a temperature between 100° and 160° C. in an autoclave in aqueous medium with ammonium hydrogen-sulfite. The 1-sulfo-6-carboxy-2-naphthol is isolated from the reaction mixture in a conventional manner by carefully pouring the reaction batch onto ice. The precipitated product is filtered off with suction and suspended in ice-water, and any sulfuric acid still present is neutralized with sodium carbonate by adjusting the suspension to a pH between 4 and 4.5. The compound can then be isolated by filtering off with suction and drying.

Provenance & Evidence