Aryl halides with organocopper compounds

There is presumably more than a subtle difference between the reactions of alkyl and aryl halides with organocopper compounds, as a straightforward nucleophilic displacement of aryl halide by the d electrons of a copper species is hardly likely. Simple aryl halides are nearly all inert to the usual nucleophiles, such as alkoxides, unless strongly activated by electron-attracting groups in the ortho and para positions. However, coordination of the halogen to copper may be sufficient to... 

Since then, experiments have been reported which indicate that (1) organocopper compounds will couple with aryl halides (2) arylcopper compounds can be oxidatively and thermally dimerized (3) arylcopper compounds are intermediates in the Ullmann reaction (4) organocopper compounds are intermediates in copper-catalyzed decarboxylations and (5) copper-promoted coupling reactions are not restricted to aromatic halides. The copper(I) oxide-promoted coupling reactions, however, have still to yield firm evidence of a copper intermediate. 

The Rosenmund-von Braun reaction involves the treatment of aryl halides with Cu CN or a 2 1-mixture of K CN/Cul in pyridine, quinoline or an appropriate aprotic polar solvent such as A-methylpyrrolidine (NMP), DMF, DMAC, HMPA at temperatures ranging from 150-250°C". This reaction has been postulated to proceed via organocopper intermediates. The reactivity of aryl-halogen bonds is in the order I > Br > Cl F. The difference in reactivity between Ar-Br and Ar Cl is normally sufficient to permit selective cyanation of the Ar—Br bonds (for example, compounds 2 and 3 ) (Figure 7.2). Discrimination between Ar—Br and Ar—1 bonds, however, is more difficult to accomplish, and therefore mixtures of iodo- and bromo-substituted aryl [ C]nitriles can be expected whenever iodo, bromo aryl dihalides are employed The selechve replacement of iodine... 

Organocopper and cuprate compounds can couple with aryl halides in moderate to good yields (Stephens and Castro, 1963 Curtis and Taylor, 1966 Castro et al., 1966, 1969 Rausch et al., 1966, 1969 Make and Castro, 1967 Corey and Posner, 1967, 1968 Atkinson et al., 1967a,b,c, 1969 Vig et al., 1969 MladenoviS and Castro, 1968 Whitesides et al., 1969a ... 

The organocopper compounds react mainly with halides and they also react with aryl compounds, acetals, tosylates (R-0S02-C6H4CH3(-/7)) and tolyflates (R-OSO2CF3). The reactions with halides are first order to each of the concentrations and they are Sn2 reactions. The order of reactivity of alkyl halides regarding the alkyl group is as follows ... 

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