The chrysanthemumcarboxylic acids I.—Preparation of the chrysanthemic acids

The large‐scale laboratory preparation of (±)‐cis‐ and (±)‐trans‐chrysanthemic [2: 2‐dimethyl‐3‐isobutenylcyclopropane‐I‐carboxylic] acids is improved, in view of their importance as components of synthetic pyrethrins, e.g. allethrin. A short series of esters from (±)‐cis‐ and (±)‐trans‐chrysanthemic acids containing either —[CH2]n.C6H4CI‐p, where n = o, 1, and 2, or —CH2.CO.C6H4C1‐p, or —CH2.CC13 groups as the alcoholic components is prepared, representing DDT‐pyrethrin hybrids. Insecticidal testing shows these esters to be substantially non‐toxic to houseflies.