Esterification of (±)‐cis‐ and (±)trans‐chrysanthemic acids in methanolic sulphuric acid gives the expected methyl chrysanthemates together with methyl δ‐methoxydihydro‐chrysanthemates. Normal esterification of the carboxyl group is accompanied, in part, by acid‐catalysed addition of methanol to the ethylenic bond of the isobutenyl group. Methyl (±)‐cis‐δ‐methoxydihydrochrysanthemate is also formed on methanolysis of (±)‐cis‐dihydro‐chrysanthemo‐δ‐lactone. Ozonization of the methyl chrysanthemates, followed by hydrogenolysis of the ozonides, gives methyl (±)‐cis‐ and (±)‐trans‐3‐formyl‐2: 2‐dimethylcyclopropane‐I‐carboxylates in low yield. The (±)‐trans‐aldehydo‐ester is also obtained, though also in low yield, by Rosenmund reduction of (±)‐trans‐3‐carbomethoxy‐2: 2‐dimethylcyclopropane‐I‐carbonyl chloride and by Raney‐nickel hydrogenolysis of ethyl (±)‐trans‐3‐carbomethoxy‐2: 2‐dimethylcyclopropane‐I‐carbothiolate, both prepared from (±)trans‐caronic acid.

The special reactivity of N,N-dialkylaniline N-oxides allows practical and convenient access to electron-rich aryl halides. A complementary pair of reaction protocols allow for the selective para-bromination or ortho-chlorination of N,N-dialkylanilines in up to 69% isolated yield. The generation of a diverse array of halogenated anilines is made possible by a temporary oxidation level increase of N,N-dialkylanilines to the corresponding N,N-dialkylaniline N-oxides and the excision of the resultant weak N- O bond via treatment with thionyl bromide or thionyl chloride at low temperature.

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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.