Systematic Syntheses and Characterization of Dodecadien-1-olswith Conjugated Double Bond, Lepidopterous Sex Pheromones

Abstract

Four geometrical isomers of 5,7-, 6,8-, 7,9- and 8,10-dodecadien-l-ols were systematically synthesized by two routes. One involved the Wittig reaction between (2s)-2-alkenal and a phosphorane with an appropriate carbon chain, and yielded a mixture of (E, Z)- and (E,E)-isomers in a ratio of ca. 3:2. The other route comprised of the Wittig reaction of a 2-alkynal and the stereoselective reduction of the triple bond to a (Z)-double bond via hydroboration with di-cyclohexylborane to give a mixture of (Z, Z)- and (Z, E)-isomers in a ratio of 6:1 ~ 10:1. Both the mixtures were separately chromatographed on a silica gel column impregnated with silver nitrate to give four geometrically pure isomers. With 9,11-diene they were analysed by GC on a capillary column, HPLC, silver nitrate impregnated TLC, and ¹³C NMR.