Oxidative coupling, of alkynes

There have also been several reports of the cyclization of diynes with amines under the influence of copper(I) chloride (equation 73) (65CB98, 70KGS125, 72TL3487). This is a potentially useful reaction for symmetrically substituted pyrroles, since symmetrical diynes can be obtained by oxidative coupling of alkynes. 

The stoichiometric head-to-head oxidative coupling of alkynes with CpRuBr(COD) affords a metallacyclic biscarbene complex [22], This process has been used to initiate catalytic formation of the RCH=CH-CH=C(Y)R backbone, to produce Junctional dienes from alkynes by addition of H-Y. The complex [Cp RuCl(COD)[ successfully catalyzes this new chemical transformation, involving the combination of two molecules of alkynes and one molecule of carboxylic acid to afford functional conjugated dienes (Scheme 4) [23]. 

Chapter 50 Oxidative Coupling of Alkynes 2,7-Dimethyl-3,S-octadiyn-2,7-diol... 

Scheme 1.13. Oxidative coupling of alkyne and nitrile molecules to produce benzene and pyridine...

The oxidative coupling of alkynes is even easier than that of alkenes it leads to metallacyclopentadienes as in the examples below. In the last case, the X-ray crystal stmctnre indicates that the stmctnre is closer to the bis-carbene-ruthenium form than to the ruthenacyclopentadiene mesomer form, and Nishihara showed that this chemistry can be extended to the synthesis of conjngated polymeric mthenacycles starting from 1,3-bntadiyne. - ... 

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