SYNTHESIS OF CIS-JASMONE AND OTHER CIS-RETHRONES

Convenient three-stage syntheses (32-35% overall) of cis-jasmone and cis-cinerone, from readily available 3-(5-methyl-2-furyl)propionaldehyde (2) are described. Wittig reactions, under 'salt-free' conditions are used for the cis-alkenylation (ca. 12% trans is concurrently produced). Use of an allyl Wittig reagent (3c) led to a mixture (2:3) of cis- and trans-dienes which was converted into a mixture of cis- and trans-pyrethrone, from which cis-pyrethrone was separated and characterised. Thermal rearrangement of cis-pyrethrone gave isopyrethrone.