Patent ID: 6392058
Filing Date: 2002-05-21
Classification: C07D

Abstract:
A process for preparing a 1-substituted 5- and/or 3-hydroxypyrazole of the formulae I and II, respectively in which R1 is C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C3-C6-cycloalkyl or C1-C4-alkoxy, where these groups may be substituted by halogen, C1-C4-alkoxy, phenoxy, C1-C6-alkoxycarbonyl, C1-C6-alkylthiocarbonyl or by a cyclic ring system having 3-14 ring atoms, which comprises reactingc) an alkyl vinyl ether of the formula V â€ƒin which R2 is C1-C6-alkyl or C3-C6-cycloalkyl with phosgene VIa, â€œdiphosgeneâ€  VIb or â€œtriphosgeneâ€  VIc to give an acyl chloride of the formula VII d) converting this by elimination of hydrogen chloride into the corresponding 3-alkoxyacryloyl chloride of the formula VIII â€ƒand e) esterifying this with an alcohol of the formula IX â€ƒin which R3 is C1-C6-alkyl or C3-C6-cycloalkyl to give the corresponding alkyl 3-alkoxyacrylate of the formula III, and reacting said alkyl 3-alkoxyacrylate of the formula III with a hydrazine of the formula IV in which R1 is as defined abovea) at a pH of 6-11 to give 5-hydroxypyrazoles of the formula I or b) at a pH of 11-14 to give 3-hydroxypyrazoles of the formula II.