A new synthesis of (3E, 5Z)-1.3,5-undecaniene (2) is presented. based on a Munnich addition to 1.4 decadiyne, followed by L&&r hydtogenation and H&aan elimbtadon. 'PItis "one pot" coupling of C7+C3+Cl syntbons affords 2 stereochemically pure. Following thek discovery in the essential oil of galbanum (Fe& galban@~) [l] and Hawaian seaweed (Dictyopteris plugiogrumma) [2], the four stereoisomem of 1,3,!&undecatriene 2 were synthe.sised and submitted for olfactive evahtation [3].
The (3ZSZ)isomer is known to be unstable, readily isomerising to 3 by a 1.7 sigmatropic shift, while the (3E, SE)-isomer possesses only a weak galbanum note. The most interesting galbanm kagmnce is exhibited by the (31% SZ)-isomer 2, motivating the publication of several non-stereoselective [4] and stemoselective syntheses F-81.
Nevertheless, none of them has become eligible for a viable industrial process, due to economic reasons (price, availability of starting materials), ecological considerations, safety problems (akrgenic and carcinogenic pmperks of the intermediates) or simple technical aspects such as prohibitive dilution conditions.
We therefore decided to design a synthesis based on the following prerequisites: a) cheap, available and inoffensive starting materials b) simple and classical industrial transformatious c) simple purhicadon techniques. In view of the crucial last step of the most recent stereo&xtive synthesis (scheme 1) [Sil, Scheme 1