Process for the preparation of pyrrole derivates

Process for the preparation of a pyrrole compound of the formula I ##STR6## in which R and R.sup.1, independently of each other, denote hydrogen or (C.sub.1 -C.sub.4)-alkyl;

• R.sup.2 denotes (C.sub.1 -C.sub.3)-alkyl which is substituted by a radical selected from the group consisting of --NH.sub.2, acylamino of the general formula II ##STR7## formyl, mono- or di- (C.sub.1 -C.sub.4)-alkoxymethyl, (C.sub.1 -C.sub.4)-alkoxycarbonyl and cyano;
• X denotes oxygen or sulphur;
• and
• R.sup.3 denotes a radical selected from the group consisting of hydrogen, (C.sub.1 -C.sub.5)-alkyl, (C.sub.5 -C.sub.7)-cycloalkyl, phenyl or phenylamino, amino and (C.sub.1 -C.sub.5)-alkylamino, by the Vilsmeier formylation reaction of a compound of the general formula III ##STR8## in which R, R.sup.1 and R.sup.2 are defined as specified above, with a disubstituted formamide and a catalyst in a degradable organic solvent, hydrolysing the reaction product to produce an organic solvent phase and an aqueous phase, both phases containing amounts of the desired formylated pyrrole derivative, separating the phases, extracting the formylated pyrrole derivative from the aqueous phase by means of a water-miscible organic extractant and adding it to the organic solvent phase, and purifying the formylated pyrrole derivative by high vacuum distillation of the organic solvent phase in a short path evaporator.