Glaser coupling

Modifications

Eglinton reaction

In the related Eglinton reaction two terminal alkynes are coupled by a copper(II) salt such as cupric acetate. :2R-!{\equiv}!-H -[\overset{}\ce{Cu(OAc)2}][\ce{pyridine}] R-!{\equiv}!-!{\equiv}!-R

The oxidative coupling of alkynes has been used to synthesize a number of natural products. The stoichiometry is represented by this highly simplified scheme:

:[[File:Eglinton Reaction Mechanism 1.jpg]] Such reactions proceed via copper(I)-alkyne complexes.

This methodology was used in the synthesis of cyclooctadecanonaene. Another example is the synthesis of diphenylbutadiyne from phenylacetylene.

Hay coupling

The Hay coupling is variant of the Glaser coupling. It relies on the TMEDA complex of copper(I) chloride to activate the terminal alkyne. Oxygen (air) is used in the Hay variant to oxidize catalytic amounts of Cu(I) to Cu(II) throughout the reaction, as opposed to a stoichiometric amount of Cu(II) used in the Eglington variant. The Hay coupling of trimethylsilylacetylene gives the butadiyne derivative.

Scope

In 1882 Adolf von Baeyer used the method to prepare 1,4-bis(2-nitrophenyl)butadiyne, en route to indigo dye.

Shortly afterwards, Baeyer reported a different route to indigo, now known as the Baeyer–Drewson indigo synthesis.

References

References

1. (1870). "Untersuchungen über einige Derivate der Zimmtsäure". Annalen der Chemie und Pharmacie.
2. (1869). "Beiträge zur Kenntniss des Acetenylbenzols". Berichte der Deutschen Chemischen Gesellschaft.
3. (1959). "Macrocyclic Acetglenic Compounds. Part I. ''cyclo''-Tetradeca-1:3-diyne and Related Compounds.". J. Chem. Soc..
4. Eglinton, G.; McRae, W. Adv. Org. Chem. '''1963''', 4, 225.
5. K. Stöckel and F. Sondheimer. (1974). "[18]Annulene".
6. I. D. Campbell and G. Eglinton. (1965). "Diphenyldiacetylene".
7. (1962). "Oxidative Coupling of Acetylenes. II". The Journal of Organic Chemistry.
8. Graham E. Jones, David A. Kendrick, Andrew B. Holmes. (1987). "1,4-Bis(trimethylsilyl)buta-1,3-diyne". Organic Syntheses.
9. (1882). "Ueber die Verbindungen der Indigogruppe". Berichte der Deutschen Chemischen Gesellschaft.
10. (21 May 2012). "Palladium-Catalyzed Cross-Coupling: A Historical Contextual Perspective to the 2010 Nobel Prize". Angewandte Chemie International Edition.