A stereoselective formation of (Z)-2-methyl-2-alkenol by the Wittig reaction: its application to a synthesis of nerylacetone and (Z,Z)-farnesylacetone.
The Wittig reaction of benzyloxyacetone or tetrahydropyranyloxyacetone with 4-pentynylidenetriphenylphosphorane in salt-free conditions followed by removal of the protecting group afforded (Z)-2-methylhept-2-en-6-yn-1-ol in 95–96 % stereoselectivity. After conversion of the allylic alcohol to the corresponding bromide, the latter was coupled with prenyl or neryl p-tolyl sulfone, followed by reductive desulfonation and hydration of the acetylenic bond, to give nerylacetone and (Z,Z) -farnesylacetone, respectively.