Diynes, synthesis

A recent synthesis of a conjugated triendiyne, fraws-bupleurynol, exemplifies the use of the conjugated diyne synthesis developed above to the synthesis of natural products121,153 (Scheme 55). 

Zhang, D. H., Zhang, Z. and Shi, M. 2012. Transition metal-catalyzed carbocycUzation of nitrogen and oxygen-tethered l,n-enynes and diynes Synthesis of five or six-membered heterocychc compounds. Chem. Commun. (Camb.) A% %3) 10271-10279. 

Kessabi J, Beaudegnies R, Jung PM, Martin B, Montel F, Wendebom S (2008) A convenient, high-yielding copper-free synthesis of skipped 1,4-diynes. Synthesis 655-659... 

The synthesis can be conducted both in solution and without solvents. The reaction in solvent (e.g., methanol, ethanol, dioxane, dimethylformamide) is recommended for volatile 1,3-diynes and amines in this case the pyrroles are purer and the yield is higher. With disubstituted diacetylenes, ammonia and primary alkyl- and arylamines produce 1,2,3-trisubstituted pyrroles under the same conditions (65CB98 71MI1). Since disubstituted diacetylenes are readily obtained by oxidative coupling of acetylenes (98MI2), this reaction provides a preparative route to a wide range of pyrroles. 

The Ratnberg-Backlund reaction has been used for the preparation of strained unsaturated ring compounds that are difficult to obtain by other methods. A recent example is the synthesis of ene-diyne 5" that has been used as starting material for a Bergman cyclization ... 

An important stage in the synthesis has been reached. It was anticipated that cleavage of the trimethylsilyl enol ether in 18 using the procedure of Binkley and Heathcock18 would regiospecifically furnish the thermodynamic (more substituted) cyclopentanone enolate, a nucleophilic species that could then be alkylated with iodo-diyne 17. To secure what is to become the trans CD ring junction of the steroid nucleus, the diastereoisomer in which the vinyl and methyl substituents have a cis relationship must be formed. In the... 

The total synthesis of ( )-estrone [( )-1 ] by Vollhardt et al. is a novel extension of transition metal mediated alkyne cyclotrimeriza-tion technology. This remarkable total synthesis is achieved in only five steps from 2-methylcyclopentenone (19) in an overall yield of 22%. The most striking maneuver in this synthesis is, of course, the construction of tetracycle 13 from the comparatively simple diyne 16 by combining cobalt-mediated and ort/io-quinodimethane cycloaddition reactions. This achievement bodes well for future applications of this chemistry to the total synthesis of other natural products. 

Some researchers have elaborated synthesis of PCSs employing bis(nitrile oxide)s as 1,3-dipoles and diynes, dinitriles, and a number of other compounds as dipolaro-philes154-156). 

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

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