NEW SYNTHESIS OF UNSATURATED ACIDS .V. APPLICATION TO CYCLOALKENE-1-CARBOXYLIC AND BETA,GAMMA-UNSATURATED ACIDS

The method of converting 4-halo-4-substituted 2-pyrazolin-5-ones into α,β-unsaturated acids by treatment with aqueous alkali has been extended to the 3,4-polymethylene derivatives (II, X = CI or Br; n = 4-6) although the reaction was unsuccessful in the case of the trimethylene derivative (II, X = CI or Br; n = 3). It has also been possible to extend the reaction to the synthesis of β,γ-unsaturated acids. Treatment of 3-(bromomethyl)-4,4-dimethyl-2-pyrazolin-5-one (X) with sodium hydroxide gave 2,2-dimethyl-3-butenoic acid. The precursor (X) was obtained by treatment of ethyl γ-bromo-α, α-dimethylacetoacetate with hydrazine or NBS bromination of 1 -acetyl-3,4,4-trimethyl-2-pyrazolin-5-one (XIII). © 1969, American Chemical Society. All rights reserved.