Enynes and Diynes

The three isomeric Z-cyclo-octenynes have been prepared using thermal of butyl-lithium-induced decomposition of 1,2,3-selenadiazoles to introduce the triple bonds.  

A convenient route to hex-2-en-4-yn-l-ols functionalized (OH, OMe, NMea) at the 6-position involves reaction of a lithium or sodium acetylide with 

An unprecedented base-catalysed reversal of a conjugated enyne system has been reported. When treated with stoicheiometric quantities of potassium amide in liquid ammonia, or with catalytic quantities of potassium t-butoxide in DMSO or HMPA, the enynamines (71) isomerize almost completely to the reversed ynenamines (72).  

Allylic trimethylsilanes smoothly couple with propargylic dicobalt complexes of the type (74) at 0 C to give, following decomplexation, 1,5-enynes. Elec- 

Verboom, R. H. Everhardus, J. W. Zwikker, and L. Brandsma, Reel. Trav. Chim. Pays-Bas, 1980, 99, 325. 

Under phase-transfer conditions, alkenyl halides (298) couple with acetylenes, using Pd as a catalyst, to give 1,3-enynes (299) in which the configuration of the vinyl halide is retained in the final product. High stereoselectivity is also 

Haruta, M. Ishiguro, K. Furuta, A. Mori, N. Ikeda, and H. Yamamoto, Chem. Lett., 1982, 1093. 

Okamura and van Kruchten have extended the synthesis of allenyl sulphoxides to the preparation of the vinylallenyl sulphoxides (318) by addition of phenyl-sulphenyl chloride to the alkenynols (317).  

Corey and Kang have developed the coupling of vinylcopper reagents with iodoallenes to enynes, providing useful syntheses of 5,6-, 11,12-, and 8,9-dehydroarachidonic acids.For example, addition of the cuprate that is generated from the vinylstannane (319) to the iodo-allene (320) furnishes 11,12- 

Guindon et al. have reported a total synthesis of optically active leukotriene Bi (325). The key step in the synthesis was the base-catalysed opening of the tetrahydrofuran (323), obtained from 2-deoxy-D-ribose, to give the triene (324). 

A full report of the ruthenium-catalysed codimerization of terminal acetylenes with 1,3-dienes has appeared. Yields are somewhat variable, but the method offers an attractive and direct route to a 

The cyclic dienynyl triflate (34) was prepared from the parent 

The first examples of linear co-dimerization of acetylenes with buta-l,3-diene have been reported. Aliphatic terminal acetylenes (196) react with buta-1,3-diene in the presence of a catalytic amount of an appropriate ruthenium complex at 60-80 C to give almost quantitative yields of E-conjugated enynes (197).  

Organocuprates add to 1,3-diynes to give regioisomeric mixtures of adducts by contrast, organoargentates, which are less reactive, add regiospecifically to 

Mitsudo, Y. Nakagawa, H. Watanabe, K. Watanabe, H. Misawa, and Y. Watanabe, J. Chem. Soc., Chem. Commun., 1981,496. 

3-Dilithiopropargyl phenyl sulphide (204) reacts cleanly with allylic bromides to give high yields of phenylthio-substituted 1,5-enynes (205). Following re-metallation at the terminal position to prevent reduction of the triple bond, the phenylthio group is easily removed by treatment with lithium in liquid ammonia. The overall procedure is at least 99% stereoselective.  

There have been some data6 available on the absorption of molecules with two acetylenic linkages in conjugation (diyne). Diynes show at least three well-defined maxima around 230 m/x (e 350), 240 m/x ( r 400) and 250 m/x (e 220). Substitution and change of solvent do not seem to affect these bands to any appreciable extent. 

It was mentioned in the preceding chapter that an isolated ethylenic linkage gives a high intensity (e 10,000) band near 190 m/x and that an 

Substituents markedly affect the position of the it - tt bands (K-bands) in ajS-unsaturated carbonyl derivatives. Woodward4 has studied the effect of alkyl substituents on a -unsaturated ketones in detail and has shown that the absorption maxima for the different types of substituted a/8-unsaturated 

Evans and Gillam7 have proposed empirical generalizations for the substituent effects on the bands of a/ -unsaturated aldehydes (Table 4.5). Data on the absorption spectra of a few a/ -unsaturated aldehydes are summarized in Table 4.6. The n rr bands of the carbonyl group in a/3- 

Compound i 1 Nature of substi- tution 7T tt band (K-band) l n - 77 band (R-band)  

Trost has disclosed some new chemistry of allylic sulphones which 

A very elegant stereoselective preparation of conjugated dienynes utilises a [2,3] Wittig rearrangment - Peterson 

In another approach, conjugated dienynes were constructed by 

Thus a dihydro LTB methyl ester (37) as well as other 

Dienyl triflates can also be used in such couplings to give the 122 

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Diene, Enyne, and Diyne Metathesis in Natural Product Synthesis... 

Depending on the types of unsaturated functional units involved in the metathesis process, the reactions can be classified into three major categories diene, enyne, and diyne metathesis (Figs. 1-3). Another mode of classification... 

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