Prepn. of pigments from (O)-amino thiophenols - condensed with dihalo maleic acid or derivs. in (N)-methyl pyrrolidone

摘要

Prepn. of pigments of formulae (I) and (II): (in which R is H, Cl, Br Me, OMe, OEt or SO2Me) by condensn. of 2 mols. o-aminophenol of formula: with 1 mol. acid or formula: or its anhydride or 1-4C alkyl diester, in N-methyl pyrrolidone (I) as reaction medium and in absence of alkali. High yields of pigment are obtd. of high purity giving improved brilliance and fastness compared with that from known processes of condensn. in other solvents in presence of acid acceptors.