Imidazolinone herbicides: Synthesis and novel chemistry

The imidazolinone herbicides were prepared from reaction of an α‐ methylvaline fragment with an o‐dicarboxylic acid. Early syntheses were completed through an imide amide intermediate, such as I or XV, followed by further cyclization to 2,5‐diones III or XXI. Reaction of these diones with nucleophiles led to imidazolinones IV and V. The significant and interesting activity of these compounds led to new and versatile methods of synthesis, including resolution of the α‐methylvaline fragments, development of a metallation‐carboxylation route, a one‐step picoline to imidazolinone route, and several pyridine and fused‐ring pyridine syntheses.