Copper, organo- compounds halides

Coupling of acetylenes and halides, copper-promoted, 50,100 Cuprous chloride, reaction with an organo-magnesium compound, 50,98... 

Burdon et al. 31) have proposed that aryl and vinyl halides, but not alkyl halides, couple with copper compounds via a four-center transition state (XI). Nucleophilic substitution of vinylic bromides by organo-... 

These methods of acylation are devices to solve the problem that acid chlorides and organo-lithium or magnesium derivatives are not good partners. To get good acylation with acid chlorides, as well as good alkylation with alkyl halides, we need to turn to other metals which provide softer carbanion complexes, less basic compounds with metals showing a lower affinity for oxygen. The most important is copper. 

The difficulties of direct oxidative insertion with metals other than Mg or Li mean that o-complexes are often made from organo-lithium or Grignard reagents by metal exchange. This reaction amounts to a nucleophilic substitution at the metal without a change of oxidation state so the metal is used in whatever oxidation state is finally needed. Attack of methyl lithium on a Cu(I) halide gives methyl copper 50, a o-complex of Me- and Cu(I). If an excess of MeLi is present an ate complex is formed, lithium dimethylcuprate 51. This is formally a compound of a copper anion 51a, just as BF4 is a borate. The term ate complex refers to such formally anionic complex in which the metal has one extra anionic ligand. Its true structure is dimeric 51b and it exists as an equilibrium with 52 in solution.20... 

The Cadiot-Chodkiewcz and Glaser reactions are the synthetic reaction with acetylene type compounds. As the acetylene compounds easily form stable organo-copper compounds, these acetylenecopper compounds react directly with halides to afford the acetylene derivatives. This synthetic reaction is called the Castro reaction [43]. For example, as shown in eq. (22.22), aryl compounds having functional groups such as OMe, NO2 and COOH are able to condense with copper acetylides... 

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