Cadiot-Chodkiewicz coupling

The Cadiot-Chodkiewicz coupling in organic chemistry is a coupling reaction between a terminal alkyne and a haloalkyne catalyzed by a copper(I) salt such as copper(I) bromide and an amine base [Chodkiewicz, W. Ann. Chim. Paris 1957, 2, 819-869.] [Cadiot,P.; Chodkiewicz, W. In Chemistry of Acetylenes; Viehe, H. G., Ed.; Marcel Dekker: New York, 1969; pp 597-647.] . The reaction product is a di-acetylene or di-alkyne.

The reaction mechanism involves deprotonation by base of the acetylenic proton followed by formation of a copper(I) acetylide. A cycle of oxidative addition and reductive elimination on the copper center then creates a new carbon carbon bond.

Related couplings are the Glaser coupling and the Eglinton coupling.

Cadiot-Chodkiewicz coupling

In one study ["Synthesis of 1,4-Cyclohexadiene-Based Acetylenic Macrocycles with Cadiot-Chodkiewicz Coupling. Structure of a Tub-Shaped Tetrameric Container" Arkasish Bandyopadhyay, Babu Varghese, and Sethuraman Sankararaman J. Org. Chem.; 2006; 71(12) pp 4544 - 4548; (Article) DOI|10.1021/jo0605290] the Cadiot-Chodkiewicz coupling has been applied in the synthesis of acetylene macrocycles starting from "cis-1,4-diethynyl-1,4-dimethoxycyclohexa-2,5-diene". This compound is also the starting material for the dibromide through NBS and silver nitrate:

The coupling reaction itself takes place in methanol with piperidine, the hydrochloric acid salt of hydroxylamine and copper(I) bromide.

Eglinton reaction

In the related Eglinton reaction [G. Eglinton and A. R. Galbraith, J. Chem. Soc., 889 (1959).] two terminal alkynes are coupled directly a copper(II) salt such as cupric acetate. This procedure was used in the synthesis of cyclooctadecanonaene. Another example is the synthesis of diphenyldiacetylene from phenylacetylene [OrgSynth | author = I. D. Campbell and G. Eglinton | title = Diphenyldiacetylene | collvol = 5 | collvolpages = 517 | year = 1973 | prep = cv5p0517]

Glaser coupling

The Glaser coupling (1870) is by far the oldest acetylenic coupling and is based on cuprous salts like copper(I) bromide and an additional oxidant like oxygen. The base in its original scope is ammonia. [cite journal
title = Untersuchungen über einige Derivate der Zimmtsäure
author = Carl Glaser
journal = Annalen der Chemie und Pharmacie
volume = 154
issue =
pages = 137
year = 1870
url =
doi = 10.1002/jlac.18701540202] [cite journal
title = Beiträge zur Kenntniss des Acetenylbenzols
author = Carl Glaser
journal = Berichte der deutschen chemischen Gesellschaft
volume = 2
issue =
pages = 422–424
year = 1869
url =
doi = 10.1002/cber.186900201183]

Hay coupling

The Hay coupling (1962) is another version of the Glaser coupling with the TMEDA complex of copper(I) chloride [cite journal | title = Oxidative Coupling of Acetylenes. II | author = Allan S. Hay | journal = J. Org. Chem. | year = 1962 | volume = 27 | issue 9 | pages = 3320–3321 | doi = 10.1021/jo01056a511] .An example is the the coupling of trimethylsilylacetylene [OrgSynth | title = 1,4-Bis(trimethylsilyl)buta-1,3-diyne | author = Graham E. Jones, David A. Kendrick, and Andrew B. Holmes | collvol = 8 | collvolpages = 63 | year = 1993 | prep = cv8p0063]

References