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Alkynyllithium compounds

The reaction of alkynyllithium compounds with alkoxycarbene tungsten complexes leads to anionic propargyl tungsten complexes (Figure 2.33 see also Figure 3.9). These intermediates are stable at low temperatures and react upon Lewis acid catalysis with aldehydes or A -sulfonyl imines to yield five-membered heterocycles [280]. Oxidative methoxycarbonylation [375] of the intermediate vinyl tungsten complex, followed by elimination of methanol leads to pyrroles or furanes (Figure 2.33 Entry 6, Table 2.22). [Pg.65]

Gold(I) acetylide complexes have been prepared from alkynyllithium compounds [Eq. (22)] (63), and a dimeric complex [(PhC=C)Au(/u.-dpe)-Au(C=CPh)] [dpe = bis(diphenylphosphino)ethane] was obtained analogously. The simplest acetylide complexes are perhaps those containing only acetylide ligands. The compounds [Au(C=CPh)]x and [Au(C=C-/-Bu)]4 (1) contain cr- and 7r-bonded acetylide groups, the values of... [Pg.48]

Neutral alkynylcopper compounds are not prepared by transmetalation of alkynyllithium compounds. Rather, they are obtained by partially deprotonating terminal alkynes with amines and capturing the ammonium acetylide formed at equilibrium with Cul (—> R-C=C-Cu + R3NH I example Figure 16.7). Copper(I) cyanide couples with aryl iodides and -bromides in a similar fashion as alkynylcopper compounds (which may well be conceived as their carba analogs). [Pg.695]

Peterson and coworkers were the first who showed that 1-alkenes can react with lithium dispersion under relatively mild conditions to give the corresponding 1 -alkynyllithium compounds and lithium hydride as the major products. Thus 1 -hexene 113 was converted into 1-hexynyllithium 116 in 65% yield within 1 h at the reflux temperature of the olefin (64 °C). It is reasonable to assume that 1,2-dilithio-hexane 114 is formed first loosing lithium hydride to give 1-hexenyllithium 115, which was detected as a side-product in 4% yield. [Pg.31]

The enantioselective addition of dialkylzinc reagents to alkynyl aldehydes catalysed by ( )-(+)-(l-methylpyrrolidin-2-yl)diphenylmethanol has been described. Thus the laevorotatory alcohol 102 was obtained in 78% enantiomeric excess (equation 15). The action of diethylaluminium chloride on alkynyllithium compounds yields ether-free diethylalkynylalanes 103, which undergo conjugate addition to nitroalkenes (equation 16). Conjugate addition also occurs in the reactions of (l-alkynyl)diisopropoxyboranes 104 (R = Bu, t-Bu or Ph) with a,j5-unsaturated ketones 105 (R = H, Me or Ph R = Me, hexyl or Ph) (equation 17). ... [Pg.299]

As previously commented for other acetylenic anions, functionalized alkynyllithium compounds of the type XXK were prepared almost exclusively by deprotonation of the corresponding terminal alkynes. Thus, the dihydropyran derivative 217 has been used for the convergent synthesis of trans-fused polytetrahydropyr-ans, which are present in marine toxins by coupling with triflates [180]. [Pg.35]

A different strategy towards <5-functionalized alkynyllithium compounds consists in the treatment of gem-dibromoaDcenes (accessible from the corresponding aldehydes) with an excess of -BuLi. Following this methodology, intermediate 219 was prepared from the dithiane derivative 218 and alkylated with methyl iodide to give the corresponding alkyne 220 (Scheme 2.29) [181]. [Pg.35]

Molander has reported the synthesis of functionalized alkynyl trifluoroborates by transmetallation of alkynyllithium compounds with boronates followed by in situ treatment with KHFjIlll]. These alkynyl trifluoroborates are crystalline solids possessing excellent air stability and are shown to undergo facile cross-coupling for example with 4-bromobenzonitrile to give functionalized arylacetylenes in high yields. Thus, the reaction is tolerant to a variety of sensitive functional... [Pg.87]


See other pages where Alkynyllithium compounds is mentioned: [Pg.38]    [Pg.110]    [Pg.85]    [Pg.426]    [Pg.327]    [Pg.167]    [Pg.110]    [Pg.20]    [Pg.20]    [Pg.490]    [Pg.287]    [Pg.317]    [Pg.31]    [Pg.31]    [Pg.35]    [Pg.37]   
See also in sourсe #XX -- [ Pg.20 ]




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1-Alkynyllithiums

Alkynyllithium

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