| abstract |
The invention relates to a method for the production of 1-substituted 5-hydroxypyrazoles of formula (I) wherein R1 is C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkinyl, C3-C6-cycloalkyl or C1-C4-alkoxy, whereby these groups can be substituted by halogen, C1-C4-alkoxy, phenoxy, C1-C6-alkoxycarbonyl, C1-C6-alkylthiocarbonyl or a cyclic ring system with 3-14 ring atoms, by reacting a) an alkylvinylether of general formula (III) wherein R2 is C1-C6-alkyl or C3-C6-cycloalkyl, with phosgene (IVa), 'diphosgene' (IVb) or 'triphosgene' (IVc) to form acid chlorides of formula (V), b) transforming said acid chlorides by eliminating hydrogen chloride into the corresponding 3-alkoxyacrylic acid chloride of formula (VI) and c) reacting said acid chloride with hydrazines of formula (VII) wherein R1 has the above cited meaning, to form 5-hydroxypyrazoles of formula (I). |