Linear trans-quinacridone

摘要

Linear trans quinacridone is prepared by heating 2,5-dianilinoterephthalic acid with a carboxylic acid chloride in an inert solvent. This would normally yield the difficulty filterable alpha-form. The beta-form (I) was only previously obtained by carrying out the reaction in the presence of pyridine bases, this process giving poor yield and being relatively uneconomic. If reaction is carried out in presence of an increased conc. of HCl (II) the reaction mixt. (I) is obtained in high purity and good yield. This may be achieved by passing (II) into the reaction mixture and maintaining a slightly raised pressure.