Sobti and Dev of the Malti-Chem Research Centre in Nadesari, vadodara, India published this method for chrysanthemic acid in 1974.

A lactone is eventually formed and the ring is opened by the use of a Grignard reagent to give (+)-trans-chrysanthemic acid.

The starting material (S)-4-hydroxy-3-methyl-2-(2-propynyl)-2-cyclopenten-1-one (7) is also commercially available as the alcohol moiety of ETOC.

Tetrakis(triphenylphosphine)palladium(0), copper(I) iodide, triethylamine, and vinyl bromide are added to (7) to add two more carbons and form (8).

The final step is the addition of an activated zinc compound to reduce the triple carbon bond to form the cis product, (S)-pyrethrolone (9).