Enyne synthesis

Enantiomers, preferential crystallization of 59 Endo selectivity 798 Ene reactions 808, 809 Enones, synthesis of 732 Enthalpies of formation 102, 103 Enynes, synthesis of 956 Enzymatic kinetic resolution 829 Epimerization 399 Episulphides, oxidation of 237 Episulphones 650, 775 Episulphoxides, photolysis of 742 a,/J-Epoxysulphones reactions of 811, 812 rearrangement of 685 synthesis of 612 / ,y-Epoxysulphones 781 y,<5-Epoxysulphones 627, 628 Epoxysulphoxides reactions of 613 rearrangement of 744 synthesis of 327, 612 Erythronolides 831... 

Bromoalkynes also couple with vinylstannanes readily to result in enynes. Synthesis of protected enynals via cross-coupling of vinylstannanes with 1-bromoalkynes in the presence of a catalytic amount of Pd(II) has been reported (equation 143)252. Hiyama and coworkers extended the Stille methodology for sequential three-component coupling of trimethylstannyl(trimethylsilyl)acetylene with a vinyl iodide in the first step and cross-coupling of the intermediate trimethylsilylethyne with another alkenyl iodide in the presence of tris(diethylamino)sulphonium trimethyldifluorosilicate in the second step to generate a dienyne (equation 144)253. Both steps occur under palladium catalysis, in one-pot, to result in stereodefined l,5-dien-3-ynes. 

Reports on ruthenium catalytic activity focus more on mechanistic consideration of the prototypical phenylacetylene dimerization than in establishing its synthetic applicability. It is not unusual that changing the alkyne substituents results in reversed selectivity (i.e. R = Ph or SiMe3 gave ( )- or (Z)- isomers, respectively) [27]. Competitive alkyne cyclotrimerization (R = COOMe) [27] or butatriene formation (R= CH2Ph, Bu) [10, 21] have occasionally been reported as possible drawbacks in enyne synthesis. The operating mechanism restricts the reaction to terminal alkynes. 

Enyne synthesis. Ethynyl cyclopiopyl carbinols undergo dehydrative metallation on exposure to the Ru complex, the metallocarbenoids thus formed are attacked by common nucleophile (e.g., H2O, ArNH2) at a cyclopiopyl carbon. The different carbenoids originated from ynoxy triflates engage in tpyo-substitution. ... 

Betzer J-F, Pancrazi A (1999) Water as a Proton Source in Regio- and Chemoselective Stannylcupration of Afkynes and Enynes. Synthesis 629... 

The palladium-catalyzed enyne synthesis is achievable via the decarboxylative coupling of propiolic acids with alkenyl bromides (Scheme 4.62) [63]. Propiolic acids also couple with benzyl halides through decarboxylation and subsequent sp C-sp C bond formation (Scheme 4.63) [64]. 

Jeffrey, C.S. (2004) Master thesis. Part I The epoxidation of 1.0 mg of geraniol. Part 11 Relay ring closing metathesis (RRCM) Selectivity in tandem enyne synthesis. University of Minnesota, Minneapolis, MN. 

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