Preparation of pyrazole and its derivatives

US5569769A · kind A · utility

Assignee

• BASF SE

Inventors

• Hans Rupert Merkle · Ludwigshafen, DE
• Erich Fretschner · Neckarsteinach, DE

Key dates

• Filing date: Feb 15, 1996
• Grant date: Oct 29, 1996
• Expiry date: Feb 15, 2016

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07D249/08
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

A process for preparing pyrazole and its derivatives of the formula I ##STR1## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each hydrogen, halogen, nitro, carboxyl, sulfonyl or C-organic radicals, from alpha,beta-unsaturated carbonyl compounds of the formula II ##STR2## and hydrazine or hydrazine derivatives of the formula III EQU H.sub.2 N--NHR.sup.4 III wherein, initially without additional diluent, an alpha,beta-unsaturated carbonyl compound of the formula II is reacted with hydrazine or a hydrazine derivative of the formula III, and the resulting reaction mixture is reacted in another step with a mixture of sulfuric acid and iodine or a compound which liberates iodine or hydrogen iodide.