Preparative scale syntheses of isomerically pure (10E,12E,14Z)- and (10E,12E,14E)-hexadeca-10,12,14-trienals, sex pheromone components of Manduca sexta

Short, efficient syntheses yielding products of very high isomeric purity h ave been developed for (10E,12E, 14Z)-hexadeca-10,12,14-trienal 1 and the ( 10E,12E,14E)-isomer 2, the key pheromone components of the tobacco hornworm moth Manduca sexta. The penultimate (EEZ)-trienol, and aldehyde 1, were fr eed from isomeric impurities by selective reaction of the impurities with t etracyanoethylene. (EEE)-Aldehyde 2 was prepared by Wittig reaction of (2E, 4E)-hexa-2,4-dienyltriphenylphosphonium bromide with 10-acetoxydecanal, dep rotection, selective crystallization of the (EEE)-trienol from the resultin g mix of isomers, and oxidation. The yield of the (EEE)-trienol was increas ed further by iodine-catalyzed isomerization of the mix of isomers in the l iquor, and further recrystallization.