Highly stereo- and regioselective palladium-catalyzed syntheses of (3E,Z)-,(3E,5E)-, and (3Z,5E)-1,3,5-undecatriene

Abstract (3E,5Z)-1,3,5-Undecatriene ( 3 ) having 98.2% stereoisomeric purity has been prepared by a new and expeditious route involving two selective Pd-catalyzed carbon-carbon bond forming reactions. The key step of this synthesis is a highly diastereoselective Pd-catalyzed cross-coupling reaction between 1-heptynylzinc chloride ( 11a ) and a molar excess of (E)/(Z)-1,2-dibromoethylene ( 12 ). Another highly diastereoselective Pd-catalyzed reaction, which involves a cross-coupling between trimethylsilylethynylzinc chloride ( 15 ) and molar excesses of stereoisomeric mixtures of 1-bromo-1-alkenes ( 16 ), has been used to prepare (E)-1-trimethylsilyl-3-nonen-1-yne ( 10a ), a key intermediate for the synthesis of (3E,5E)- and (3Z,5E)-1,3,5-undecatriene, ( 4 ) and ( 5 ). Compounds 3 and 4 , isolated from the essential oil of Ferula galbaniflua , also occur together with compound 5 in the male attracting oils of seaweeds. These substances have odors highly appreciated in perfumery.