Cyclopropanecarboxylic acid esters

Fig. 8 Modification of the acid moiety, (a) Cyclopropanecarboxylic acid esters, (b) Non-cyclopropanecarboxylic acid esters...

Alkylation of cyclopropanecarboxylic acid esters,6 Deprotonation of methyl silyloxycyclopropanecarboxylates (1), prepared as shown, is possible with LDA in THF at — 78°. The resulting anions react with primary alkyl iodides and benzylic or allylic bromides to give 2 in high yield. These products are cleaved by F to methyl 4-ketocarboxylates 3. 

With the correct choice of reaction conditions, however, the asymmetric synthesis of cis-suh-stituted cyclopropanecarboxylic acid derivatives is achieved. Stereoselective methylene transfer to (Z)-a, -unsaturated acyl systems bonded to optically active carbonyl()j -cyclopen-tadienyl)triphenylphosphanyliron 2 and oxidative decomplexation of the products gave cis-substituted cyclopropanecarboxamides 3. High asymmetric induction (up to 92% de) was observed with bromine/l-phenylethylamine as decomplexation agent. When the decomplexation was carried out with A-bromosuccinimide/ethanol, racemic cw-substituted cyclopropanecarboxylic acid esters were obtained. 

Jautelat, M., Arlt, D., Lantzsch, R.. Fuchs. R.A.. Riebel, H., Schroeder, R., and Hamisch, H., Styryl-cyclopropanecarboxylic acid esters and intermediates, Bayer, German Patent Appl. DE 2916321,1980 Chem. Abstr, 94, 121121, 1981. 

Cyclopropanecarboxylic acid esters from 2-bromocyclobutanone ketals... 

Cyclopropanecarboxylic acid esters by abnormal Hofmann degradation of quaternary ammonium salts via their hydroxides... 

For example, cycloaddition of carbethoxycarbene (from ethyl diazoacetate as precursor) on XXXIV (R=methyl, Cl, Br) in the presence of various rhodium carboxylates yields cyclopropanecarboxylic acid esters (pyrethroids) that are useful for their insecticidal activity [56] (slightly volatile, biodegradable, non toxic for mammalians). 

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