Alkynes copper catalysts

The two reactions described above can be applied for the synthesis of symmetrical -acetylenes only. Unsymmetrical bis-acetylenes can be prepared by using the Cadiot-Chodkiew icz reaction For that method a terminal alkyne 1 is reacted with a bromoalkyne 8 in the presence of a copper catalyst, to yield an unsymmetrical coupling product 9 ... 

Ethyl diazopyruvate, under copper catalysis, reacts with alkynes to give furane-2-carboxylates rather than cyclopropenes u3) (Scheme 30). What looks like a [3 + 2] cycloaddition product of a ketocarbenoid, may actually have arisen from a primarily formed cyclopropene by subsequent copper-catalyzed ring enlargement. Such a sequence has been established for the reaction of diazoacetic esters with acetylenes in the presence of certain copper catalysts, but metallic copper, in these cases, was not able to bring about the ring enlargement14). Conversely, no cyclopropene derivative was detected in the diazopyruvate reaction. 

Potassium tert-butoxide reacts with copper iodide to generate a copper / -butoxide species 98 (Scheme 29). Activation of the alkyne 94 by this copper catalyst (intermediate 96) allows the enolate attack to afford the cyclic... 

Palladium-catalysed C-C bond formation under Heck reaction conditions, which normally requires anhydrous conditions and the presence of copper(I) salts, is aided by the addition of quaternary ammonium salts. It has been shown that it is frequently possible to dispense with the copper catalyst and use standard two-phase reactions conditions [e.g. 18, 19]. Tetra-/i-butylammonium salts catalyse the palladium-catalysed reaction of iodoarenes with alkynes to yield the arylethynes in high yield [20, 21], whereas the reaction with 3-methylbut-1 -yn-3-ol (Scheme 6.30) provides a route to diarylethynes [22]. Diarylethynes are also formed from the reaction of an iodoarene with trimethylsilylethyne [23], Iodoalkynes react with a,p-unsaturated ketones and esters to produce the conjugated yne-eneones [19],... 

Oxidative homo-coupling of terminal alkynes using copper catalyst in the presence of oxygen. 

CuBr/QUINAP System The CuBr/QUlNAP system was initially used in the enan-tioselective synthesis of proparyl amines via the reaction of alkynes and enamines (Scheme 5.5). It was rationalized that the enamines reacted with protons in terminal alkynes in the presence of copper catalyst to form zwitterionic intermediates in which both the generated iminiums and alkyne anions coordinate to the copper metal center. After an intermolecular transfer of the alkyne moiety to the iminium ion, the desired products were released and the catalyst was regenerated. The combination of CuBr as catalyst and the chiral ligand QUEMAP is crucial for the good reactivities and enantioselectivities seen in the reaction. Another potential... 

The reaction of monosubstituted alkynes with iodopyrroles in the presence of palladium and copper catalysts leads to the formation of pyrrolylalkynes (79IZV1661, 80IZV726). The preformed phenylethynylcopper(I) derivative also reacts with the iodopyrroles and it is probable that an Ullmann-type mechanism prevails. 

Over the last few years it has become clear that rhodium(II) acetate is more effective than the copper catalysts in generating cyclopropenes.12 126 As shown in Scheme 28,12S a range of functionality, including terminal alkynes, can be tolerated in the reaction with methyl diazoacetate. Reactions with phenyl-acetylene and ethoxyacetylene were unsuccessful, however, because the alkyne polymerized under the reaction conditions. 

The cyclopropanation of alkenes, alkynes, and aromatic compounds by carbenoids generated in the metal-catalyzed decomposition of diazo ketones has found widespread use as a method for carbon-carbon bond construction for many years, and intramolecular applications of these reactions have provided a useful cyclization strategy. Historically, copper metal, cuprous chloride, cupric sulfate, and other copper salts were used most commonly as catalysts for such reactions however, the superior catalytic activity of rhodium(ll) acetate dimer has recently become well-established.3 This commercially available rhodium salt exhibits high catalytic activity for the decomposition of diazo ketones even at very low catalyst substrate ratios (< 1%) and is less capricious than the old copper catalysts. We recommend the use of rhodium(ll) acetate dimer in preference to copper catalysts in all diazo ketone decomposition reactions. The present synthesis describes a typical cyclization procedure. 

Functionalized cyclopropenes are viable synthetic intermediates whose applications [99.100] extend to a wide variety of carbocyclic and heterocyclic systems. However, advances in the synthesis of cyclopropenes, particularly through Rh(II) carboxylate—catalyzed decomposition of diazo esters in the presence of alkynes [100-102], has made available an array of stable 3-cyclopropenecarboxylate esters. Previously, copper catalysts provided low to moderate yields of cyclopropenes in reactions of diazo esters with disubstituted acetylenes [103], but the higher temperatures required for these carbenoid reactions often led to thermal or catalytic ring opening and products derived from vinylcarbene intermediates (104-107). 

Note that no product formation could be obtained in absence of the iron or copper catalyst. Without copper, the iron catalyst generates only stoichiometric amounts (with respect to iron) of an alkenyliron species, which is not reactive towards further transformations such as transmetallation or polymerization. A cuprate, generated by CuBr and ArMgBr, did not undergo carbometallation with the alkyne. These results indicate that the main role of the copper catalyst is most likely to promote the metal... 

Perez-Balderas F, Ortega-Munoz M, Morales-Sanfrutos J et al (2003) Multivalent neogly-coconjugates by regiospecific cycloaddition of alkynes and azides using organic-soluble copper catalysts. Org Lett 5( 11) 1951—1954... 

Cross-coupling reactions 5-alkenylboron boron compounds, 9, 208 with alkenylpalladium(II) complexes, 8, 280 5-alkylboron boron, 9, 206 in alkyne C-H activations, 10, 157 5-alkynylboron compounds, 9, 212 5-allylboron compounds, 9, 212 allystannanes, 3, 840 for aryl and alkenyl ethers via copper catalysts, 10, 650 via palladium catalysts, 10, 654 5-arylboron boron compounds, 9, 208 with bis(alkoxide)titanium alkyne complexes, 4, 276 carbonyls and imines, 11, 66 in catalytic C-F activation, 1, 737, 1, 748 for C-C bond formation Cadiot-Chodkiewicz reaction, 11, 19 Hiyama reaction, 11, 23 Kumada-Tamao-Corriu reaction, 11, 20 via Migita-Kosugi-Stille reaction, 11, 12 Negishi coupling, 11, 27 overview, 11, 1-37 via Suzuki-Miyaura reaction, 11, 2 terminal alkyne reactions, 11, 15 for C-H activation, 10, 116-117 for C-N bonds via amination, 10, 706 diborons, 9, 167... 

The addition of alkoxycarbonylcarbene derived by catalysed decomposition of methyl diazoacetate to several simple, and in particular terminal, alkynes leads to low yields S7), but the reaction with 1 -trimethylsilylalkynes proceeds reasonably efficiently subsequent removal of the silyl-group either by base or fluoride ion provides a route to l-alkyl-3-cyclopropenecarboxylic acids. In the same way 1,2-bis-trimethylsilyl-ethyne can be converted to cyclopropene-3-carboxylic acid itself58 . The use of rhodium carboxylates instead of copper catalysts also generally leads to reasonable yields of cyclopropenes, even from terminal alkynes 59). 

The reaction of elemental silicon with a gaseous mixture of hydrogen chloride and unsaturated hydrocarbons such as alkenes (e.g., ethylene and propylene) and alkyne such as acetylene in the presence of copper catalyst also affords the corresponding organodichlorosilanes. 

Another palladium catalysed reaction that has been successfully performed in water is the direct coupling of acid chlorides with alkynes.Copper is used as a CO catalyst and the choice and use of a surfactant are essential to the success of the reaction (Figure 3.10). 

Using this route, a variety of tricyclo[2.1.0.0 ]pentanes are available from cyclopropenes, with the latter being most easily prepared from the metal-catalyzed reaction of a diazo compound and an alkyne (see Section 1.2.1.2.1. for related reactions). Alkyl- and aryl-substituted cyclopropenes 1 react with copper catalysts, such as copper powder, to yield the tricyclic products 2 in low to moderate yield. ... 

Cp2TiCl2-catalyzed hydromagnesation of alkynes, alkenes, and conjugated dienes has been described in Section 3.2, in which the method of preparation of organomagnesium compounds was discussed. Here, carbomagnesation of acetylenic bonds in the presence or absence of a copper catalyst will be discussed. 

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