Preparation of 2-aminobenzothiazoles
AssigneeEastman Kodak Company
InventorsR. Donald Clark, Herman S. Pridgen
Life of this patent
Estimating the term…
Abstract
Disclosed is a process for the preparation of 2-aminobenzothiazoles by the oxidative ring closure of an arylthiourea which comprises contacting the arylthiourea with sulfuric acid and a catalytic amount of a bromine compound.
Claims5
In a process for the preparation of 2-aminobenzothiazoles by the oxidative ring closure of an arylthiourea, the improvement comprising the step of contacting the arylthiourea dissolved in sulfuric acid with a catalytic amount of bromine, hydrogen bromide, sodium bromide, potassium bromide or ammounium bromide.
In a process for the preparation of 2-aminobenzothiazole having the formula ##STR5## by the oxidative ring closure of an arylthiourea having the formula ##STR6## the improvement comprising the step of contacting the aryl thiourea dissolved in sulfuric acid having a concentration of at least about 85% with a catalytic amount of bromine of hydrogen bromide at a temperature of about 20.degree. to 120.degree. C., wherein R.sup.3 represents hydrogen, lower alkyl, lower alkoxy, chlorine, lower alkylsulfonyl or nitro and R.sup.4 represents hydrogen, lower alkyl, lower alkoxy or chlorine.
In a process for the preparation of 2-aminobenzothiazole, 2-amino-6-methylbenzothiazole, 2-amino-6-nitrobenzothiazole, 2-amino-6-methylsulfonylbenzothiazole or 2-amino-6-chlorobenzothiazole by the oxidative ring closure of phenylthiourea, p-tolythiourea, p-nitrophenylthiourea, p-methylsulfonylphenylthiourea or p-chlorophenylthiourea, the improvement comprising the step of contacting the arylthiourea dissolved in sulfuric acid with a catalytic amount of bromine, hydrogen bromide, sodium bromide, potassium bromide or ammonium bromide.
Dependencies are inferred from the claim text.