Coupling reactions: of alkynes

The influence of iron(III) salts on coupling reactions of alkynes and aldehydes (Scheme 10, routes B and C) was also explored. In these routes, a new stereoselective coupling of alkynes and aldehydes was unmasked, which led to ( ,Z)-1,5-dihalo-1,4-dienes (route B, Scheme 10) and/or ( )-a,p-unsamrated ketones (route C, Scheme 10) [27]. 

The coupling reactions of alkynes and aldehydes catalyzed by iron(III) salts have been discussed above (Scheme 10, routes B and C). The three-component coupling of aldehydes, alkynes, and amines is equivalent to the coupling reaction between alkynes and imines. Wang et al. reported such a three-component coupling catalyzed by FeCls in the absence of any ligand (Scheme 17) [33]. 

Another example of the addition of terminal alkynes to C=N in water is the coupling of alkynes with in-situ-generated A-acylimines (Eq. 4.32) and A-acyliminium ions (Eq. 4.33). In 2002, Li et al. developed a coupling reaction of alkynes with A-acylimines and A-acyliminium ions mediated by Cu(I) in water to generate propargyl amide derivatives.57 Either an activated imine derivative or imininum derivative was proposed as the intermediate, respectively. 

Trost s group examined the possibility of carrying out cross-coupling reactions of alkynes and transformed this into a very powerful synthetic method. Either homocoupling or perhaps, more interesting, heterocoupling procedures were performed using catalytic amounts of a palladium salt (Equation (191)). 

Preparation and Reaction of Zirconacyclopentadienes Table 2.1. Cross-coupling reactions of alkynes on zirconocene... 

Cross-coupling reactions of alkynes with (Z)-vinylic tellurides under PdCyCuI catalysis gives rise to the corresponding enynes and enediynes with retention of the configuration."... 

A catalytic cycle was recently proposed to account for the coupling reaction of alkynes with vinylic tellurides promoted by PdCl2.304... 

Several copper(I)-catalyzed coupling reactions of alkynes or diynes with Co3 clusters proceed with the deposition of insoluble black materials which have v(CO) spectra typical to those of the CCo3(CO)g clusters described above.438 Similar products were obtained when HCsCMgBr was used. Thermal decomposition of 286 at 100 °C gives conducting aggregates, which continue to show v(CO) absorptions and are soluble in non-aqueous solvents.480 The conductivity appears to be associated with partial decarbonylation and formation of granular microcrystalline materials. 

Rearrangement processes of alkyltitanocene dichlorides that occur under electron impact have been investigated using deuterium labelling. A novel type of zirconium-mediated coupling reaction of alkynes with vinyl bromide to afford 2,3-disubstituted dienes has been reported (see Scheme 105), and an inter-intramolecular reaction sequence has been proposed for the observed formation of vinylcyclohexadienes and/or methylenecycloheptadienes from the copper-catalysed reaction of zirconacyclo-pentadienes with allylic dichlorides. The essential step in these processes appears to be transmetallation of the zirconium-carbon bond of the zirconacyclopentadiene to produce a more reactive copper-carbon bond. New phosphorus heterocycles, e.g. (417), have been constructed by the thermal rearrangement of a [l,4-bis(trimethylsilyl)->/ -cyclooctatetraene]- ,3,5-triphospha-7-hafhanorbomadiene complex (416). 

Which cross-coupling reaction of alkynes uses palladium(O), cop-per and a base ... 

Pyridopyrimidines and pyrimidines fused with five- or six-membered heterocycles can be prepared via the ring closure of intermediate ethynylpyrimidines, which are themselves obtained by the Pd-catalyzed cross-coupling of halopyrimidines with alkynic compounds (Scheme 34). ° ""° o-Alkynylanilines such as (51), which are made by Pd-catalyzed coupling reactions of alkynes with o-haloaniline precursors, are easily cyclized to the indoles in the presence of base (Scheme 35). " " Similar meth( s can be employed in the synthesis of isocoumarins," thienopyridines," furopy-ridines" and the marine alkaloid asptamine." ... 

We have applied cross-coupling reactions of alkynes and aryl bromides to prepare the structurally well-defined polybinaphthyl crown ethers. A racemic binaphthyl crown ether monomer roc-75 [18,62] is polymerized with roc-33 in the presence of tetrakis(triphenylphosphine) palladium(O) and copper iodide to generate a polybinaphthyl crown ether 76 (Scheme 32). This polymer is soluble in organic solvents and has been characterized by various spectroscopic methods. GPC analysis shows that 76 has a molecular weight of 30,000 and M = 12,000 (PDI = 2.4). The UV spectrum of the polymer shows the maximum absorptions - max = 246, 300, and 354 nm. 

G. S. and Lu, X.Y. (2002) Palladium(II)-catalyzed coupling reactions of alkynes and allylic compounds initiated by intramolecular carbopalladation of alkynes. Tetrahedron Lett., 43, 6791-6794 (d) de Meijere, A. and Meyer, F.E. (1995) Fine feathers make fine birds - the Heck reaction in modem garb. Angew. Chem. Int. Ed., 33, 2379-2411, and references therein. 

Oxidative coupling reactions of alkynes with other unsaturated fragments... 

Takahashi T, Xi Z, Fischer R et al (1997) Intermolecular coupling reaction of alkynes with vinyl bromide with selective skeletal rearrangement. J Am Chem Soc 119 4561-4562... 

More recent applications of the Sonogashira reaction in PUFA synthesis include Spurs and Rodriguez s synthesis of maresin 1 (56) [72], a potent anti-inflammatory lipid mediator derived from DHA (7). As shown in Scheme 3.21, the Sonogashira cross coupling reaction of alkyne 82, bearing an unprotected secondary alcohol, with vinyl iodide 83, provided compound 84. Then, removal of the TES group, Boland reduction of the triple bond, and subsequent hydrolysis of the methyl ester afforded maresin 1 (56). 

Cross-coupling reactions of alkynes. Terminal alkynes undergo high yield Pd(0) catalyzed coupling reaction (72-76) with organic electrophiles. The electrophiles include vinyl, aryl, and heteroaryl halides (72-75) vinyl triflates (77J8) aryl (56,78) and heteroaryl triflates (75,78) and polyfluorophenyl perfluoroalkane sulfonates (79). Several examples are shown in equation 23 - 27 (respectively references 78,72,73,78,79). 

Polymers From Cross-Coupling Reactions of Alkynes. 

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