Synthesis of cis-jasmone and other cis-rethrones

Abstract

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. Witting reactions, under' salt-free conditions are used for the cis-alkenylation (ca 12%trans is concurrently produced). Use of an allyl Witting 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 gavi isopyrethrone.