Process for the preparation of pure 1-phenyl-3-carbalkoxy-5-hydroxypyrazoles
US4837335A · kind A · utility
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Key dates
| Filing date | Apr 4, 1988 |
| Grant date | Jun 6, 1989 |
| Priority date | — |
| Expiry date | Apr 4, 2008 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07D231/22
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
Process for the preparation of pure 1-phenyl-3-carbalkoxy-5-hydroxypyrazoles of the general formula ##STR1## in which R denotes methyl or ethyl, by reaction of acetylsuccinic esters with phenyldiazonium chloride and a base with pK.sub.B value of 3.6 to -1.5 at a pH of 4 to 9 in an aqueous medium to give the corresponding phenylhydrazone, which is cyclized at a pH of 7 to 9.5, with warming and with the addition of ammonia, to give the ammonium salt of the hydroxypyrazole. Compound I is formed by acidification.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.