10-Undecenoic Acid, an Inexpensive Source for the Synthesis of the Pheromones of Cotton Pests, Peach Tree Borer and Cherry Tree Borer

The aldehyde 7, derived from 10-undecenoic acid (5) on cis-selective Wittig reaction with pentylidenetriphenylphosphorane, subsequent deprotection and oxidation gave the pheromone (11Z)-hexadecenal (1). Wittig-Horner olefination of 1 with the phosphonate 9 furnished the conjugated ester 10 which on base catalyzed isomerization to the (3Z)-ester 11 followed by LAH reduction and acetylation gave (3Z,13Z)-octadeadien-1-yl acetate (2). Compound 10 on the other hand was chemoselectively reduced and acetylated to furnish the pheromone (2E,13Z)-octadeadien-1-yl acetate (4). For the synthesis of (3E,13Z)-octadeadien-1-yl acetate (3), 1 was condensed with malonic acid under modified condition to afford the acid 13 which was converted to 3 by standard reaction protocol.