A facile synthesis of racemic aggregation pheromones of palm pests, Rhinoceros beetle and Rhynchophorus weevil

Abstract

Pheromones of palm pests were successfully synthesized using a Grignard coupling as the key step. The synthesis of ethyl 4-methyloctanoate (1), the Oryctes rhinoceros L. aggregation pheromone, was achieved from 2-bromohexane via two pathways with overall yields over 40%. 4-Methyl-5-nonanol (2), and 4-methyl-5-nonanone (3), Rhynchophorus ferrugineus Oliv. aggregation pheromones, were synthesized by nucleophilic addition of a Grignard reagent to an aldehyde to afford a diastereoisomeric mixture of alcohols with varying ratios of threo and erythro isomera, and then oxidized with Jones reagent in overall yields of over 75%.