Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
---Methyl 3-methoxy-2-trifluoromethylacrylate 1, readily prepared by Wittig reaction from methyl 3,3,3-trifluoropyruvate, has been treated with a number of aryl- (or hetaryl-) hydrazines. Under mild base-catalysis, the resulting 3-hydrazinoacrylates 6 undergo consecutive hydrogen fluoride elimination and intramolecular nucleophilic addition to afford methyl 1-(het)aryl-5-fluoropyrazole-4-carboxylates 7. 5-Aminopyrazoles 8 have been obtained by direct reaction of the ester 7a with a lithium amide, whereas 5-fluoro-1-phenylpyrazole-4-carboxamides 10 have been formed by condensation of the 5-fluoro-1-phenylpyrazole-4-carboxylic acid 9 with amines.
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