| Glaser coupling | |
|---|---|
| Named after | Carl Andreas Glaser |
| Reaction type | Coupling reaction |
| Identifiers | |
| Organic Chemistry Portal | glaser-coupling |
| RSC ontology ID | RXNO:0000098 |
TheGlaser coupling is a type ofcoupling reaction. It is by far one of the oldest coupling reactions and is based on copper compounds likecopper(I) chloride orcopper(I) bromide and an additional oxidant like air. The base used in the original research paper isammonia and the solvent is water or an alcohol.The reaction was first reported byCarl Andreas Glaser [de] in 1869.[1][2] He suggested the following process on his way todiphenylbutadiyne:
| Eglinton reaction | |
|---|---|
| Named after | Geoffrey Eglinton |
| Reaction type | Coupling reaction |
| Identifiers | |
| Organic Chemistry Portal | eglinton-reaction |
| RSC ontology ID | RXNO:0000099 |
In the relatedEglinton reaction two terminal alkynes are coupled by a copper(II) salt such ascupric acetate.[3]
The oxidative coupling of alkynes has been used to synthesize a number ofnatural products. The stoichiometry is represented by this highly simplified scheme:[4]
Such reactions proceed viacopper(I)-alkyne complexes.
This methodology was used in the synthesis ofcyclooctadecanonaene.[5] Another example is the synthesis ofdiphenylbutadiyne fromphenylacetylene.[6]
The Hay coupling is variant of the Glaser coupling. It relies on theTMEDA complex ofcopper(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.[7] The Hay coupling oftrimethylsilylacetylene gives the butadiyne derivative.[8]
In 1882Adolf von Baeyer used the method to prepare 1,4-bis(2-nitrophenyl)butadiyne, en route toindigo dye.[9][10]
Shortly afterwards, Baeyer reported a different route to indigo, now known as theBaeyer–Drewson indigo synthesis.
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