Concise Preparation of the (3E,5Z)-Alkadienyl System. New Approach to the Synthesis of Principal Insect Sex Pheromone Constituents

Abstract

A new rapid and low-cost preparation of the (3E,5Z)-3,5-alkadienyl system, encountered in several insect pheromone constituents, was developed. Knoevenagel condensation of (E)-2-alkenals with ethyl hydrogen malonate in dimethyl sulfoxide, in the presence of a catalytic amount of piperidinium acetate, led to a mixture of geometrical isomers of ethyl 3,5-alkadienoates and ethyl 2,4-alkadienoates, from which the (3E,5Z)-3,5-alkadienoate was conveniently separated, by the use of urea inclusion complex formation. The importance of this procedure has been illustrated by the preparation of the (3E,5Z)-3,5-tetradecadienoic acid (megatomoic acid) 1, the (3E,5Z)-3,5-dodecadienyl acetate 2, and the (3E,5Z)-3,5-tetradecadienyl acetate 3. These compounds are the main components of insect sex pheromones and constitute synthetic targets of considerable interest for the semiochemical community.

The Reactivity of Epoxides with Lithium 2,2,6,6-Tetramethylpiperidide in Combination with Organolithiums or Grignard Reagents

“…To demonstrate the potential of the above methodology for diene formation, we applied the method to the total synthesis of the pheromone of the roller leaf moth, ( 3E ,5 Z )-dodecadienyl acetate 20 (Scheme ); the moth is the most economically important insect pest on apples in southern Brazil . The key step in our synthesis was the coupling between Z -alkenyllithium 18 and epoxide 17 ; this occurred to give diene 19 in 70% yield and with a selectivity of 92:8 ( E,Z /other isomers).…”

Improved Synthesis of (3E,7Z)-3,7-Tetradecadienyl Acetate, the Major Sex Pheromone Constituent of the Potato Pest Symmetrischema tangolias (Gyen)

“…The transformation of (3 E ,7 Z )-3,7-tetradecadienoic acid ( 6 ) into the target compound was done by reduction to the corresponding alcohol 7 and subsequent acetylation to the final acetate 1 . The reduction of the acid 6 to (3 E ,7 Z )-3,7-alkadienol ( 7 ) was effected in 71% yield, with an excess of Red-Al in ether , without affecting the double bonds. The acetylation was carried out in 92% yield, under standard conditions by acetic anhydride in pyridine solution to give the final product (3 E ,7 Z )-tetradecadienyl acetate ( 1 ) in high purity (95%) .…”

Active Natural Product Scaffolds against Trypanosomatid Parasites: A Review

“…137 1,2-Dioxane derivatives can be accessed through the modification of various ,-unsaturated aldehydes through initial modification via Ragoussis' modified Knoevenagel condensation to form the corresponding skipped diene. 138 Dienes can then be converted to the 4,5-unsaturated 1,2dioxane systems through reaction with photo-generated singlet oxygen species. 139…”

“…137 1,2-Dioxane derivatives can be accessed through the modification of various α,β-unsaturated aldehydes through initial modification via Ragoussis' modified Knoevenagel condensation to form the corresponding skipped diene. 138 Dienes can then be converted to the 4,5-unsaturated 1,2dioxane systems through reaction with photogenerated singlet oxygen species. 139 Various aldehydes can be utilized in the Knoevenagel condensation, or the diene could be installed via Wittig reaction of phosphonium ylides, giving a very wide scope of possible substitutions.…”