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. The reaction product is a 1,3-diyne or di-alkyne.
The reaction mechanism involves deprotonation by base of the terminal alkyne proton followed by formation of a copper(I) acetylide. A cycle of oxidative addition and reductive elimination on the copper centre then creates a new carbon-carbon bond.
Scope Unlike the related Glaser coupling the Cadiot–Chodkiewicz coupling proceeds selectively and will only couple the alkyne to the haloalkyne, giving a single product. By comparison the Glaser coupling would simply produce a distribution of all possible couplings. In one study 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 N-bromosuccinimide (NBS) and silver nitrate:
The coupling reaction itself takes place in methanol with piperidine, the hydrochloric acid salt of hydroxylamine and copper(I) bromide.
See also Glaser coupling – Another alkyne coupling reaction catalysed by a copper(I) salt. Sonogashira coupling – Pd/Cu catalysed coupling of an alkyne with an aryl or vinyl halide Castro–Stephens coupling – A cross-coupling reaction between a copper(I) acetylide and an aryl halide
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