Synthesis of 1,3-Diynes
The Glaser Coupling is a synthesis of symmetric or cyclic bisacetylenes via a coupling reaction of terminal alkynes. Mechanistically, the reaction is similar to the Eglinton Reaction; the difference being the use of catalytic copper(I), which is reoxidized in the catalytic cycle by oxygen in the reaction medium.
The related Hay Coupling has several advantages as compared with the Glaser Coupling. The copper-TMEDA complex used is soluble in a wider range of solvents, so that the reaction is more versatile.
A recent modification enables the production of a range of unsymmetrical 1,3-diynes:
L. Su, J. Dong, L. Liu, M. Sun, R. Qiu, Y. Zhou, S.-F. Yin, J. Am. Chem. Soc., 2016, 138, 12348-12351.
A valuable alternative is the Cadiot-Chodkiewicz Coupling which also allows the preparation of asymmetric bisacetylenes.
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