Synthesis of Pyrethroid Acids

Abstract

The synthesis of chrysanthemic acid 1 as mixture of stereoisomers, as racemate of pure stereoisomers or as single optically active isomer was important before the advent of synthetic photostable pyrethroids. Because of the approved and favourable properties of pyrethrin I as a non-toxic and fast-acting contact insecticide, not only pyrethrum, but also other esters of chrysanthemic acids with similar properties are of commercial interest. Therefore cheap methods for the synthesis of this acid or even total synthesis of the natural compound deserve the attention of chemists involved in synthesis. Many interesting reactions, invoxving rearrangements, eliminations and additions were applied in the synthesis of this archetypical pyrethroid cydopropane carboxylic acid.