The use of polymer supports in organic synthesis. VIII. Solid phase syntheses of insect sex attractants

Abstract

A 2% cross-linked divinylbenzene–styrene copolymer, incorporating trityl chloride groups, (1), was used in the synthesis of insect sex attractants of Lepidoptera by two independent routes. Polymer 1 reacted with the symmetrical diols 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol to give the monoblocked polymer-bound diols 5–7, respectively. Mesylation of 5–7 gave the polymer-bound monomesylates 8–10, which on coupling with 1-lithio-1-hexyne or 1-lithio-1-butyne gave the polymer-bound alkyne trityl ethers 18–20. Alkynols, obtained by hydrolysis from polymers 18-20, were selectively reduced and acetylated to give cis-7-dodecen-1-ol acetate (28), cis-9-tetradecen-1-ol acetate (29), and cis-11-tetradecen-1-ol acetate (30), the sex attractants of Trichoplusia ni (Hübner), Spodoptera frugiperda (J. E. Smith), and Argyrotaenia velutinana (Walker), respectively. Alternatively, polymer-bound 1,7-heptanediol (33), polymer-bound 1,9-nonanediol (34), and 7 were oxidized with the Sharpless reagent (CrO2Cl2/tert-butyl alcohol/pyridine) to give polymer-bound aldehydes 35–37, which on reaction with Wittig reagents and subsequent hydrolysis and acetylation gave 28, 29, and 10-tetradecen-1-ol acetate (47), the sex attractant of Archips semiferanus (Walker). A 'reverse' Wittig synthesis of 47 was achieved by the reaction of polymer 10 with molten triphenylphosphine followed by base and treatment with butyraldehyde. Subsequent cleavage and acetylation gave 47 in high yield and stereoselectivity containing greater than 91% of the cis isomer.