2,3-octadiene-5,7 diyn

Various metal acetylides are used for smooth coupling with propargylic halides and acetates. 2,3-Alkadien-5-yn-l -ols are obtained by the reaction of 2-(l -alkynyl)oxiranes [28,29], As a synthetic application, the unstable 2,3-octadiene-5,7-diyn-l-ol (136), a fungus metabolite, has been synthesized by the coupling of 4-trimethylsilylbutadiy-nylzinc chloride (134) with 2-ethynyloxirane (135) followed by desilylation [31]. 

Scheme 11.46 Synthesis of 2,3-octadiene-5,7-diyn-l-ol 171 (fungus metabolite).

Pd-catalyzed allenylation-propargylation has hardly been applied to natural products synthesis. To date, the synthesis of ( )-2,3-octadiene-5,7-diyn-l-ol, a metabolite from fungus Cortinellus berkeleyams shown in Scheme 36, ° may well be the only example. 

Zn is the most versatile with respect to leaving groups and most satisfactory. This reaction has been applied to the synthesis of 2,3-octadiene-5,7-diyn-l-ol, a metabolite from the fungus Cortinellus berkeleyanus (Scheme 3.52) [174bj. To our knowledge, there does not appear to be any reported example of the Pd-catalyzed propargyl-alkynyl coupling. 

Therefore, 15 is 4-methyl-l,4-octadiene and not 5-methyl-4,7-octadiene. Diynes are similarly named, as in 16, where both CsC units are contained in the longest chain, so it is a hexadiyne. The chain is numbered to give both CsC units the lowest combination of numbers. The position of the CsC units in 16 dictates the position of any substituents on those chains. Diyne 16 is named 3,3-diethyl-l,5-hexadiyne. Cyclic molecules such as 1,3-cycloheptadiene (17) are named using these protocols. In these examples, the primary carbon skeleton and/or ring system is marked in purple, with substituents in green. 

Octadiene-3,5-diyne-l, 8-dimethoxy-9-octadecynoic acid Octogen (dry)... 

Of interest in this connection is the fact that cw,cw-3,5-octadiene-l,7-diyne itself has been observed spectroscopically in the hydrolysis of its 1,8-bistrimethylsilyl precursor. However, after only a few minutes at room temperature, a tetracyclic, rearranged, dimer of benzocyclobutadiene was isolated (Scheme 9.3). 

Consequently,6-tert-butyldimethylsilyl-8-trimethylsilyl-3-methyl-3-(Z)-octe-ne-l,7-diyn-5-ol serves as a latent diendiyne moiety, which on cross-coupling with aryliodides provides an easy access to a variety of diendiynes, (Z,Z)-l-aryl-3,5-octadiene-l,7-diynes. These diendiynes are precursors of 5,6-diaryldibenzo[a,e] cyclooctenes. The generation of two diendiynyl moieties (tetraentetraynes) in the same molecule produces oligomers having multiple dibenzo[a,e]cyclooctenyl units. 

Hydroboration of terminal diyne gives organoboron polymer having branched structure due to the further hydroboration reaction toward the initially formed vinylborane structures. That is, terminal diynes are taken to have a potential as a multifunctional monomer. When the polymerization between 1,7-octadiene and thexylborane was carried out in the presence of a small amount of 1,7-octadiyne, the molecular weights of organoboron polymers were found to be increased when the ratio of diyne/diene was increased [5]. 

Recently, we explored haloboration polymerization between boron tribromide and terminal diynes to give poly(organoboron halide)s as a polymeric Lewis acid, which has scarcely ever been known [13]. These poly(organoboron halide)s were also prepared by means of hydro-boration polymerization between dienes and monobromoborane as shown in Scheme 4 [14]. As a typical example, 1,7-octadiene was added to a 1.0 M dichloromethane solution of monobromoborane-dimethyl sulfide complex with stirring at 0°C under nitrogen. The molecular weight of the polymer obtained was increased when the feed ratio of monobromoborane to diene approached or slightly exceeded unity. 

---