Acylation of tert-butyl 3-(methylamino)but-2-enoate with fluorinated acetic acid anhydrides occurred at the enamine carbon atom. The reaction of the resulting tert-butyl 3-(methylamino)-2-(RFCO)but-2-enoates with alkyl hydrazines resulted in mixtures of isomeric pyrazoles that were easily separated by column chromatography. The target fluorinated pyrazole-4-carboxylic acids were obtained on a multigram scale.

Fluoroalkyl-substituted pyrazole-4-carboxylic acids can be synthesized on a multigram scale using tert-butyl 3-(methylamino)but-2-enoate and fluorinated acetic acid anhydrides.

Paper

Multigram Synthesis of Fluoroalkyl-Substituted Pyrazole-4-carboxylic Acids

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