Patent ID: 6329530
Filing Date: 2001-12-11
Classification: C07D

Abstract:
A process for preparing a 1-substituted 5-hydroxypyrazole of the formula I ##STR20##in which R.sup.1 is C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl, C.sub.2 -C.sub.6 -alkynyl, C.sub.3 -C.sub.6 -cycloalkyl or C.sub.1 -C.sub.4 -alkoxy, where these groups may be substituted by halogen, C.sub.1 -C.sub.4 -alkoxy, phenoxy, C.sub.1 -C.sub.6 -alkoxycarbonyl, C.sub.1 -C.sub.6 -alkylthiocarbonyl or by a cyclic ring system having 3-14 ring atoms, which comprisesa) reacting an alkyl vinyl ether of the formula III ##STR21##in which R.sup.2 is C.sub.1 -C.sub.6 -alkyl or C.sub.3 -C.sub.6 -cycloalkyl with phosgene IVa, ""diphosgene"" IVb or ""triphosgene"" IVc ##STR22##to give an acyl chloride of the formula V ##STR23##b) converting this by elimination of hydrogen chloride into the corresponding 3-alkoxyacryloyl chloride of the formula VI ##STR24##andc) reacting this with a hydrazine of the formula VII ##STR25##in which R.sup.1 is as defined above to give a 5-hydroxypyrazole of the formula I.