Synthesis of Insect Sex Pheromones by Ligand-Free Iron-Catalyzed Alkyl-Allyl Cross-Coupling Involving α,ω-Difunctionalized Aliphatic Grignard Nucleophiles and Allyl Electrophiles

We disclose synthetic access to four insect sex pheromones, proceeding with a key alkyl-allyl disconnection achieved by a ligand-free cross-coupling between α,ω-difunctionalized aliphatic Grignard reagents bearing terminal alkoxides and allylic electrophiles, mediated by an air-stable and inexpensive iron precatalyst. The efficiency of the coupling is ensured by a combination of exo- or endogenous magnesium alkoxide additives and LiCl, enabling appreciable, mild conditions (low 1 mol % catalyst load, noncryogenic temperatures) and proceeding with near-complete stereoselectivity.