| abstract |
The invention relates to a process for the preparation of 1-substituted 5- and / or 3-hydroxypyrazoles of formulas # in which R 1 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 6 cycloalkyl or C 1 -C 4 alkoxy. wherein these groups may be substituted by halogen, C1-C4 alkoxy, phenoxy, C1-C6 alkoxycarbonyl, C1-C6 alkylthiocarbonyl or a cyclic ring system of 3 to 14 ring atoms by reaction of an alkyl 3-alkoxyacrylate of formula @@ c which R 2 and R 3 independently represent C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl, with hydrazine of formula N @ 1 in which R 1 has the above meanings at pH a value from 6-11 to obtain 5-hydroxypyrazole of formula II or at a pH of 11-14 to obtain 3-hydroxypyrazole of formula II. |