Eglinton oxidative coupling

Although copper acetylides seem to be able to perform a nucleophilic substitution reaction at the sp-carbon atom of a bromo- or iodoacetylene (Cadiot-Chodkievicz reaction), this reaction has only rarely been used for the preparation of cyclic 1,3-diacetylenes. Copper-mediated oxidative coupling reactions (Glaser, Hay and Eglinton coupling) are more popular in this area and have attracted much attention in the construction of carbon-rich cyclic and polycyclic systems (see Chapter 13). One of the earliest carbon-rich systems of this type was the CzoHg system 19 [11,16] [Eq. (5)]. 

The Glaser reaction is an oxidative coupling of terminal alkynes 1 to yield a symmetrical Z -acetylene 2 the coupling step is catalyzed by a copper salt. Closely related is the Eglinton reaction, which differs from the Glaser reaction mainly by the use of stoichiometric amounts of copper salt as oxidizing agent. 

The Glaser coupling reaction is carried out in aqueous ammonia or an alcohol/ammonia solution in the presence of catalytic amounts of a copper-I salt. The required copper-II species for reaction with the acetylide anion R-C=C are generated by reaction with an oxidant—usually molecular oxygen. For the Eglinton procedure, equimolar amounts of a copper-II salt are used in the presence of pyridine as base. 

Oxidative coupling [Cu(OAc)2/py Eglinton] of Co -C4 (C5Hio)2 ( -C5H4C= CH) gave binuclear 322 in 82% yield oxidation potentials Ei, E2 for the two cobalt centers are -f-0.846, +0.947 V, respectively, suggesting that the two radical centers interact via the butadiynyl chain. ... 

The Eglinton Reaction is an oxidative coupling of terminal alkynes, and allows the synthesis of symmetric or cyclic bisacetylenes via reaction of the terminal alkyne with a stoichiometric amount of a copper(II) salt in pyridine. 

The oxidative coupling of two terminal alkynes via their copper acetylide complexes to form a 1,3-butadiyne function is known variously as Glaser, Eglinton, or Hay... 

Misumi and his coworkers have prepared 1,3-cycIotetradecadiyne (14S) and 1,3-cyclotridecadiyne (146) by Eglinton s oxidative coupling under high dilution conditions of the corresponding a,co-diynes - . 1,3-Tridecadiyne (146), the smallest... 

For Glaser oxidative coupling of phenylacetylene to Campbell and Eglinton used cupric acetate in pyridine-methanol. The deep blue suspension became green when refluxed (1 hr.). The cooled mixture was acidified with stirring and cooling and the product was collected by ether extraction. 

Standard oxidative coupling methods for acetylenes use the Glaser method (CuCl, NH4CI, aqueous alcohol, O2) or Eglinton and Galbraith s method [Cu(OAc)a, pyridine, alcohol]. The former reaction can be accelerated by addition of JYiV A -tetramethylethylenediamine and the yield improved by using dimethoxyethane as solvent. ... 

Another method to synthesize hosts by formation of carbon-carbon bonds is the well known Eglinton alkyne coupling. Cutting the desired cage compound retrosynthetically into two half molecules the application of this method leads to short synthetic pathways with good yields. Therefore the oxidative alkyne coupline has become more and more important for the design of supramolecular host structures and led to the development of new variants of the... 

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