Insect Pheromones; I. Synthesis of Achiral Components of Insect Pheromones

Many insect pheromones, especially those of the Lepidoptera (moths and butterflies) consist of one or more achiral mono- or polyolefinic compounds. The present article surveys significant developments in the synthesis of such achiral compounds in the last six years. The basic approaches which concern the methods used to either form a di- or a trisubstituted double bond of the mono- or polyunsaturated component of the pheromone or to link an unsaturated group to an unsaturated molecule in order to form the polyunsaturated component are discussed. 1. Synthesis from Carbonyl Compounds by Wittig and Related Reactions 2. Synthesis by Reduction of Alkynes 3. Synthesis by Controlled Carbon-Carbon-Bond Formation with Organometallic Reagents 3.1. Grignard Reagents 3.2. Organolithium Compounds 3.3. Organocopper(I) Compounds and Lithium Diorganocuprates 3.4. Organoboron Compounds 4. Synthesis by Photochemical Reactions 5. Synthesis by [3.3]-Sigmatropic Reactions 6. Synthesis by Transition Metal-Catalysed Cross-Metathesis Reactions 7. Miscellaneous Reactions 8. Conclusions