The evolution of the insecticidal pyrazoline moiety that was originally discovered in 1972 has led to the discovery of a new crop insecticide, indoxacarb, which is the first commercialized pyrazoline-type sodium-channel blocker. Both monocyclic and fused-tricyclic pyrazolines and pyridazines, as well as structurally related semicarbazones were examined prior to the discovery of analogous tricyclic oxadiazines which had similarly high activity as well as favorable environmental dissipation rates and low toxicity to non-target organisms. The eventual leading candidate, DPX-JW062, was originally obtained as a racemic molecule, but a chiral synthesis was developed which produces material that is 50% ee in the insecticidal (+)-S-enantiomer (DPX-MP062, indoxacarb).

A series of novel chiral nonracemic bis(phosphinites) derived from (R,R)-trans-2,5-tetrahydrothiophenedimethanol has been prepared. Reaction of these ligands, 6, with Rh(COD)2X (COD = cyclooctadiene, X = OS(O)2CF3, SbF6) yields rhodium complexes which have been tested in the asymmetric hydrogenation of methyl α-acetamidocinnamate, providing enantioselectivities of up to 55%. The racemic bis(diphenylphosphinite) ligand 6c binds in an unusual tridentate mode, forming the thioether-bridged species ((6c)Rh)2(OTf)2 (7). This was characterized by conventional spectroscopic methods and by single-crystal X-ray analysis.

A commercial synthesis of the DuPont herbicide azafenidin is described. Discovery of a novel synthesis of the triazolinone ring system and a practical, environmentally benign process to 5-cyanovaleramide were critical breakthroughs in enabling azafenidin to be manufactured at an acceptable cost. The process began with the selective hydrolysis of DuPont's nylon intermediate, adiponitrile, to 5-cyanovaleramide. This was converted via Hofmann rearrangement and Pinner-type cyclization to afford the key amidine carboxylate intermediate containing both carbon atoms of the triazolinone ring. The preservation of all six carbon atoms of adiponitrile set up a 2 + 3 cyclocondensation with arylhydrazines, which replaced a costly 4 + 1 cyclocondensation of an amidrazone with phosgene or a phosgene surrogate used in the original route. This new triazolinone process was optimized to afford the commercial product in a highly efficient and economical fashion.

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