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[reaction: see text] A new method for the synthesis of 1,5-diynes, from the reaction of 1,3-dilithiopropyne and propargyl chlorides, was developed. This new methodology was used to prepare (4E,6Z,10Z)-4,6,10-hexadecatrien-1-ol, one of the pheromone components of the cocoa pod borer moth Conopomorpha cramerella, in 51% overall yield.

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Propargylation of alkyl halides: ( E )‐6,10‐dimethyl‐5,9‐undecadien‐1‐yne and ( E )‐7,11‐dimethyl‐6,10‐dodecadien‐2‐yn‐1‐ol product: (E)‐6,10‐dimethyl‐5,9‐undecadien‐1‐yne byproduct: 2‐butyn‐1‐ol product: (E)‐7,11‐dimethyl‐6,10‐dodecadien‐2‐yn‐1‐ol reactant: trimethylsilyl‐protected acetylene

Sequential treatment of 2,3-dichloropropene with magnesium and n-BuLi generates the operational equivalent of 1,3-dilithiopropyne, which upon treatment with aldehydes or ketones, produces the corresponding alkoxy lithium acetylide intermediates. Reaction of this alkoxide with tosyl chloride, and t-BuLi produces 1-substituted, or 1,1-disubstituted 1,3-enynes in a one-pot reaction. When this lithium acetylide intermediates, obtained by this procedure, were used to perform palladium-catalyzed cross-coupling reactions, followed by addition of thionyl chloride and pyridine, 1,4-disubstituted or 1,1,4-trisubstituted 1,3-enynes were obtained in a one-pot protocol.

Isomeric ( E , Z )-and ( Z , Z )-hexadeca-10,12-dienal were prepared, stereospecifically, in 51% and 43% overall yields from dec-1-yne.Diaphania hyalinata and Diaphania nitidalis are pyralid species that exhibit similar life cycles and habits. The former feeds upon the foliage of pumpkin and other cucurbits, 2 whereas the latter is particularly destructive to cantaloupe, cucumber and muskmelon. 3 The damage caused make these crops unsuitable for marketing. The isomers ( E , Z )-hexadeca-10,12-dienal (1) and ( Z , Z )-hexadeca-10,12-dienal (2) were isolated, as minor components, from the extracts of ovipositors of female melonworm, D. hyalinata , 2 while trace amounts of 1 were found in extracts from pickleworm adults of D. nitidalis . 3 These compounds, along with others, represent essential components of the sex pheromones of these species. Previous syntheses of the ( E , Z )-isomer 1 have involved Wittig condensation of butyltriphenylphosphorane with ( E )-12-(2-tetrahydropyranyloxy)dodec-2-enal, 4 followed by oxidation. The major drawback of this procedure is the generation of a mixture of E and Z isomers in the Wittig reaction. The ( Z , Z )-isomer has been prepared by the Ca-diotÐChodkiewicz coupling of pent-1-yne with undec-10yn-1-ol, followed by reduction of the triple bond with dicyclohexylborane to the corresponding dienol. 2 The alcohols ( E , Z )-and ( Z , Z )-hexadeca-10,12-dien-1-ol have been synthesized stereospecifically, by the palladium-catalyzed cross-coupling reaction between an hydroxyalkenylborane and the appropriate haloalkene in the presence of a base. 5 The overall %yields reported for the syntheses of these alcohols, from undec-10-en-1-ol, are 41 and 27% respectively. 5 In this paper we report stereospecific syntheses of the isomeric dienals 1 and 2 in 51 and 43% overall yields from dec-1-yne (3) . The syntheses utilized the common precursor tert -butyldimethylsilyl undec-10-ynyl ether (6) which was prepared from dec-1-yne (3) by coupling of its lithium acetylide with paraformaldehyde, at low temperature, to give undec-2-yn-1-ol ( 4 ) in 93% (Scheme 1). The latter was isomerized to undec-10-yn-1-ol (5) in 98% by a zip-Stereospecific Synthesis of ( E , Z )-and ( Z , Z )-Hexadeca-10,12-dienal.

Sequential treatment of 2,3-dichloropropene with magnesium and n-BuLi generated the equivalent of 1,3-dilithiopropyne, which adds regiospecifically to aldehydes and ketones to produce homopropargyl alcohols. The lithium acetylide intermediate formed in this protocol can be further reacted with aromatic and vinyl halides, under palladium catalysis, to produce 4-substituted homopropargyl alcohols and 5-en-3-yn-1-ols, respectively, in one-pot with good overall yields.

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