Glaser procedure

The Glaser coupling reaction is carried out in aqueous ammonia or an alcohol/ammonia solution in the presence of catalytic amounts of a copper-I salt. The required copper-II species for reaction with the acetylide anion R-C=C are generated by reaction with an oxidant—usually molecular oxygen. For the Eglinton procedure, equimolar amounts of a copper-II salt are used in the presence of pyridine as base. 

All three coupling procedures are suitable to give high yields under mild reaction conditions. Many functional groups do not interfere. For the application in organic synthesis the Eglinton variant may be more convenient than the Glaser method a drawback however is the need for stoichiometric amounts of copper salt. 

The method is based on that described by Glaser and Sly [24]. Prepare a calibration curve and blanks according to section 4.1.3.4, subheading Procedure. ... 

Oxidative coupling of a terminal alkyne is a particularly easily performed carbon-carbon bond forming reaction, which results in a good yield of the symmetrical diacetylene. A widely used procedure involves the oxidation of the alkyne with air or oxygen in aqueous ammonium chloride in the presence of a copper(i) chloride catalyst (Glaser oxidative coupling). 

Of various homocoupling procedures derived from the original Glaser process that are still used today, Hay s procedure [4] using catalytic amounts of the biden-tate complexing base TMEDA in polar solvents (e.g. acetone, dichloromethane or o-dichlorobenzene) is most utilized and is the method favored for preparing linear oligo- and polyacetylenes, as outlined in Scheme 2 [5]. 

Table 1. Oligomerization and polymerization of compound 1 by Glaser-Hay coupling. Catalyst formation CuCI, TMEDA, and 02 in 1,2-dichlorobenzene [5, 12]. The reaction was performed in the presence of molecular sieves (4 A). If PhC=CH was available immediately at beginning ofthe coupling process (procedure C) an equal amount was added again 1 h before the end of the reaction. (tr is the total reaction time and tadd is the time until addition of the end-capping reagent.)...

Although palladium-catalyzed processes have also achieved improvements in the field of acetylenic coupling [2], the Glaser-Hay and Cadiot-Chodkiewicz copper-mediated methods still remain the most used. Further mechanistic investigations seem to be necessary, to overcome the limitations of the existing procedures, mainly poor selectivity and predictability. 

The oxidative coupling of terminal alkynes by copper salts, discovered in 1869 by Glaser, has evolved to the modified method reported in 1962 by Hay. In the Hay procedure, oxygen is passed through a solution of the alkyne and a catalytic amount of a copper(I) salt in a complex-forming solvent, such as pyridine and TMEDA. Although the oxidative coupling by Cu salt catalysts in suitable amines has wide scope, it is less successful for less acidic terminal alkynes, such as alkyl- or silyl-alkynes. 

This (and previous work) served as a partial basis for the military s instructional systems development (ISD) movement (Branson et al. 1975) and the subsequent refinement of procedures for criterion-referenced measurement technologies (Glaser 1963 Mager 1972 Swezey 1981). 

The preceding procedures characterize those mutants which have completely lost the ability to produce nitrate reductase. An alternative ingenious technique has been developed to detect mutants showing different levels of nitrate reductase (Ruiz-Herrera et al., 1969 Glaser and DeMoss, 1972). Mutagen-treated cells are plated on agar. When the colonies develop they are exposed to filter papers moistened with formate and nitrate. The filter paper is then dried and sprayed with reagent to detect nitrite. Color intensity of the... 

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