Reactions Glaser

The Glaser reaction is an oxidative coupling of terminal alkynes 1 to yield a symmetrical Z -acetylene 2 the coupling step is catalyzed by a copper salt. Closely related is the Eglinton reaction, which differs from the Glaser reaction mainly by the use of stoichiometric amounts of copper salt as oxidizing agent. 

Acetylene and terminal alkynes are CH-acidic compounds the proton at the carbon-carbon triple bond can be abstracted by a suitable base. Such a deprotonation is the initial step of the Glaser reaction as well as the Eglinton... 

The mechanism of the Eglinton and Glaser reactions probably begins with loss of a proton... 

In the Hay modification of the Glaser reaction, it was noted that the reaction could be modified to avoid isolation of the acetylide ... 

A computational study of the Glaser reaction provides additional mechanistic insight. L. Fomina, B. Vazquez, E. Tkatchouk, S. Fomine, Tetrahedron 2002, 58, 6741... 

Controlled oxidation of organometallic species may lead to the creation of a C-C bond. In acetylene chemistry, the Glaser reaction and its variations [29] are among the most ancient reactions of this type, and rely on the oxidation by air (or cupric ions) of alkynyl copper(I) species generated in situ. These very mild conditions allow the use of a large range of terminal alkynes, such as ethynylated heterocycles (Figure 7a) [26b]. 

The starting material, 2-methyl-3-butyn-2-ol, is made commercially from acetone and acetylene and is convertible into isoprene. This experiment illustrates the oxidative coupling of a terminal acetylene to produce a diacetylene, the Glaser reaction. 

Reactions of benzene solutions of arylalkynes with 1 equiv. of chloroacetone and 2 equiv. of Et.iN, using a mixture of (PPhsjaPd and Cul as a catalyst, afford 1,4-diarylbutadiynes in very good yields. Under similar reaction conditions aliphatic 1-alkynes yield a mixture of symmetrically disubstituted 1,4-dialkynyl-l,3-butadiynes and 3-alkyl-4(l-alkynyl)-hexa-l,5-diyn-3-enes (10 equations 15 and 16). 7 This method may represent a good alternative, in nonpolar organic solution, to the Glaser reaction. 

Polyynes Simple Synthesis in Solution Through the Glaser Reaction... 

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