Arylcopper reagents

The arylcopper reagents couple with 1-iodoarylacetylenes to give the unsym-metrical diarylacetylenes [25(S] (equation 176) Reaction with tetrabromoethyl- ene gives bis(pentafluorophenyl)acetylene in 66% yield [25S] (equation 177) Pen-tafluorophenyl copper couples with (bromoethynyl)triethylsilane to give C6F5C=CSi(C2H5)3 in 85% yield [259]... 

Moreover, functionalized arylcopper reagents have been reported as appropriate nucleophiles with alkenyl and dienyl sulfonates (Table 5.3, entries 14—18) [18]. Although aryl sulfonates showed little reactivity towards arylcopper reagents, alkenyl sulfonates proved to be much more reactive under the described reaction conditions. 

This is the sort of selectivity evident in the next example, which looks more complicated but is really just addition of an arylcopper reagent followed by alkylation (trans to the bulky Ar group) with an iodoester. 

Scheme 2.2. Preparation of functionalized arylcopper reagents from functionalized aryllithiums.

Arylacetylenes.3 Arylacetylenes can be prepared simply and in fairiy good yields (30-80%) by reaction of an arylcopper reagent with iodoethynyl(trimethyl)silane at 0° (3 hr.) and then at 20° (6 hr.). The protective trimethylsilyl group can be removed quantitatively by treatment with alkali.4... 

The arylcopper reagents are best prepared by addition of an ethereal or THF solution of a Grignard or an aryllithium reagent (1 mole) to a vigorously stirred suspension of freshly prepared cuprous bromide (1.1 mole) in ether. The reagent (0.8 mole) in THF is then added. 

Cupradon. Arylcopper reagents are formed with tbe Cu atom attached to a functional group (e.g., alkoxy, amide, cyano,...) of an arene, on treatment with R(TMP)Cu(CN)Li2 derived from (1). Such copper reagents can engage in hydroxylation, phenylation, alkylation,... 

P-Arylation of electron-deficient alkenes. Aryl radicals are generated from aryl halides by reaction with the CrCh-ethylenediamine complex, and the mode of addition is similar to that of arylcopper reagents. 

Cross-coupling reaction of arylcopper reagents with aryl halides... 

Electrophilic Amination. r-Butyl )V-lithio-)V-(/)-toluenesulfonyloxy)carbamate (1) is prepared from Abutyl W(/)-toluenesulfonyloxy)carbamate, which is easily obtained on a large scale by tosylation of the commercially available f-butyl )V-hydroxycarbamate. (1) is an electrophilic aminating reagent and a synthetic equivalent of +NHBoc . It reacts with alkyllithium reagents (eq 1) or arylcopper reagents (eq 2) to provide primary amines in their (V-Boc protected form. 

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