A facile route to a versatile synthon for preparation of cis-pyrethroids

$\text{cis}$-2-Cyano-3,3-dimethylcyclopropanecarboxylic acid was obtained in >50% overall yield starting with ethyl 3,3-dimethylacrylate. The key step involved a tandem Michael reaction - intramolecular displacement to afford stereoselectively a cyclopropanoid precursor of $\text{cis}$-pyrethroids.