Stereospecific Total Synthesis of the Potent Synthetic Pyrethroid NRDC 182

Article abstract of DOI:10.1021/jo01304a028

A highly stereospecific synthesis of (1R,3R)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid was devised which allowed for a total synthesis of the potent synthetic pyrethroid insecticide (S)-cyano-(3-phenoxyphenyl)methyl (1R,3R)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropancarboxylate (NRDC 182).Asymmetric reduction of 1,1,1-trichloromesityl oxide with an LAH-ephedrine complex produced (2R)-1,1,1-trichloro-2-hydroxy-4-methylpent-3-ene which was transformed to a diazoacetate ester via the corresponding diazoacetoacetate.Copper-catalyzed thermal decomposition of the diazoacetate resulted in internal carbenoid cyclization onto the olefin in nearly quantitative stereoselectivity.The resultant bicyclic lactone was ring opened via a Boord-type reaction to give the requisite cyclopropane acid which was esterified with racemic 3-phenoxybenzaldehyde cyanohydrin followed by recrystallization and epimerization of the mother liquor to produce NRDC 182.