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Alkyne derivatives reagents

Acylzirconocene chloride derivatives are easily accessible in a one-pot procedure through the hydrozirconation of alkene or alkyne derivatives with zirconocene chloride hydride (Schwartz reagent) [Cp2Zr(H)Cl, Cp = cyclopentadienyl] and subsequent insertion of carbon monoxide (CO) into the alkyl— or alkenyl—zirconium bond under atmospheric pressure (Scheme 5.1) [2],... [Pg.149]

The use of a PdCl2(PPh3)2-InBr3 reagent system catalyzes cross-coupling reactions of a variety of aryl iodides with several terminal alkynes. The corresponding functionalized alkyne derivatives are produced in good yields (Scheme 102) 351... [Pg.710]

Alt and co-workers have prepared numerous alkyl (67) and acyl (68) tungsten(II) alkyne complexes. A definitive paper detailing these results was published in 1985 (69). The reaction sequence which converts CpW-(CO)3R and free alkyne to CpW(CO)(RC=CR)R and free CO is not simple. Low temperature photolysis (-30°C) of the reagents in pentane first yields acyl alkyne products [Eq. (15)]. These products result from trapping of the initial alkyl alkyne derivative which rapidly reacts with CO to form the observed acyl product [Eq. (16), L = CO] (69). [Pg.10]

Davidson has utilized electron-withdrawing alkyne substituents to promote addition of nucleophiles to neutral cyclopentadienyl alkyne derivatives. With bisalkyne reagents the conversion of one hexafluorobutyne to an rj2-vinyl ligand provides four electrons and limits the remaining alkyne to a formal two-electron donor role. The CF3 substituents are important in both increasing the electrophilicity of the alkyne carbon and in stabilizing the N = 2 role for the intact alkyne retained in the product [Eq. (53)]. [Pg.79]

Acylzirconocene chlorides are easily accessible in a one-pot procedure through the hydrozirconation see Hydrozirconation) of alkene or alkyne derivatives with the Schwartz s reagent and subsequent migratory insertion see Migratory Insertion) of carbon monoxide into the alkyl- or alkenyl zirconium bond. The stability of the acylzirconocene chlorides is remarkable at room temperature, and consequently allows many applications in organic synthesis. [Pg.5308]

ALKYNES Dimethyl sulfoxide-derived reagent (a). Sodium methyl-sulflnylmethide. [Pg.180]

In contrast to the common methods described above, no sophisticated or powerful dehydration reagent is needed and the reaction can easily be carried out on a large scale. A reaction mechanism has been suggested, in which the aldehyde serves as a relay for the water transfer from the amide to the acetonitrile solvent. The aldehyde may be varied, but formic acid is essential for the reaction. Alkyne derivatives decompose under the reaction conditions, and both THP ethers and TBDMS groups are unstable. [Pg.392]

Reactions via Copper Reagents and Cuprates. The conjugate addition reactions of the copper-derived reagents prepared from PhMe2SiLi, their addition reactions with alkynes and al-lenes, and their use in displacements of aUyl halides and esters are covered in the relevant sections. [Pg.259]

A series of Ru-Co mixed-metal nitride and nitrene carbonyl clusters 230-236 was synthesized from the interactions of [Ru3(/x-H)2(/X3-NOMe)(GO)9] with mononuclear cobalt reagents such as [Gp Go(GO)l2] and [Gp Go(GO)2]. The alkyne derivative [Ru3(/X3-NOMe)(/X3-77 -PhG2Ph)(GO)9] has also been used. It is interesting to observe the formation of 237,... [Pg.1089]

Accordingly, iron-catalyzed coupling of tricyclo[4.1.0.0 ]hept-l-ylmagnesium bromide and related Grignard reagents with propargylic halides proceeds either in an overall Sn- or Sn fashion depending on the substitution pattern of the alkyne (Scheme 4-204). Terminal alkynes predominantly afford allenes via a Sn route, whereas trimethylsilyl-substituted alkynes lead to alkyne derivatives. ... [Pg.676]

Terminal alkyne anions are popular reagents for the acyl anion synthons (RCHjCO"). If this nucleophile is added to aldehydes or ketones, the triple bond remains. This can be con verted to an alkynemercury(II) complex with mercuric salts and is hydrated with water or acids to form ketones (M.M.T. Khan, 1974). The more substituted carbon atom of the al-kynes is converted preferentially into a carbonyl group. Highly substituted a-hydroxyketones are available by this method (J.A. Katzenellenbogen, 1973). Acetylene itself can react with two molecules of an aldehyde or a ketone (V. jager, 1977). Hydration then leads to 1,4-dihydroxy-2-butanones. The 1,4-diols tend to condense to tetrahydrofuran derivatives in the presence of acids. [Pg.52]

A valuable feature of the Nin/Crn-mediated Nozaki-Takai-Hiyama-Kishi coupling of vinyl iodides and aldehydes is that the stereochemistry of the vinyl iodide partner is reflected in the allylic alcohol coupling product, at least when disubstituted or trans tri-substituted vinyl iodides are employed.68 It is, therefore, imperative that the trans vinyl iodide stereochemistry in 159 be rigorously defined. Of the various ways in which this objective could be achieved, a regioselective syn addition of the Zr-H bond of Schwartz s reagent (Cp2ZrHCl) to the alkyne function in 165, followed by exposure of the resulting vinylzirconium species to iodine, seemed to constitute a distinctly direct solution to this important problem. Alkyne 165 could conceivably be derived in short order from compound 166, the projected product of an asymmetric crotylboration of achiral aldehyde 168. [Pg.606]

Fleming has shown (2) that the cuprate reagent (Chapter 8) derived from dimethylphenylsilyl lithium and copper(t) cyanide (molar ratio 2 1) adds regioselectively in an overall syn manner to terminal alkynes, the silyl moiety becoming attached to the terminal carbon atom (variation in reagent... [Pg.98]


See other pages where Alkyne derivatives reagents is mentioned: [Pg.110]    [Pg.264]    [Pg.213]    [Pg.8]    [Pg.14]    [Pg.78]    [Pg.87]    [Pg.90]    [Pg.416]    [Pg.1197]    [Pg.852]    [Pg.213]    [Pg.54]    [Pg.110]    [Pg.2106]    [Pg.825]    [Pg.156]    [Pg.101]    [Pg.245]    [Pg.52]    [Pg.3552]    [Pg.110]    [Pg.215]    [Pg.156]    [Pg.351]    [Pg.441]    [Pg.357]    [Pg.318]    [Pg.100]    [Pg.145]    [Pg.273]    [Pg.553]    [Pg.724]    [Pg.132]   
See also in sourсe #XX -- [ Pg.279 ]




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Alkynes : derivatives

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