gamma-Cyhalothrin → (1RS)-cis-3-(Z-2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropanecarbonyl chloride

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In order to produce gamma-cyhalothrin on an industrial scale it is desirable to find methods of making the final product that avoid the use of expensive reagents and have as few chemical stages as possible. The present invention provides a direct process to meet these requirements. There is therefore provided a process for the preparation of gamma-cyhalothrin (IV) comprising a) chlorinating 1R cis-Z 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl cyclopropanecarboxylic acid (I) to give 1R cis-Z 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl cyclopropanecarboxylic acid chloride (II) and b) esterifying 1R cis-Z 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl cyclopropanecarboxylic acid chloride (II) with the (S)-cyanohydrin of 3-phenoxy benzaldehyde (III).

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