Halides reaction with organocopper reagents

Stilbenes, photocyclization of, 30, 1 StiUe reaction, 50, 1 Stobbe condensation, 6, 1 Substitution reactions using organocopper reagents, 22, 2 41, 2 Sugars, synthesis by glycosylation with sulfoxides and sulfinates, 64, 2 Sulfide reduction of nitroarenes, 20, 4 Sulfonation of aromatic hydrocarbons and aryl halides, 3, 4 Swem oxidation, 39, 3 53, 1... 

Only perfluoro-tert-butyl copper has been prepared by this method. The compound was isolated in 72% yield from the reaction of m-(tri-fluoromethyl)phenylcopper with perfluoro-fert-butyl bromide in ether-dioxane at 0°C(34). Exchange and cross-coupling reactions occur simultaneously in many reactions between organocopper reagents and various organic halides (69, 97, 174, 217, 220, 266, 297). However, the method is only of limited use as the new reagent [R Cu in Eq. (16)] and its precursor are capable of reacting with both species of halide, RX and R X, present in the mixture. 

The majority of reported reactions of aryl and heteroaryl substrates with organocopper reagents are examples of Stephens-Castro coupling or the more recent catalytic version of that reaction. The reaction has found recent application in syntheses of C-(6)-substituted pterins and pteridines, substituted pyridines, and the antitumor antibiotic fredericamycin A," to name a few. Aryl iodide can be che-mospecifically displaced in the presence of bromide," and 2,5-dibromopyridine is regioselectively substituted at the 2-position. Substitution of halobenzenes by propargyl alcohol, followed by oxidative cleavage, provides a convenient route to terminal arylalkynes. " Fused heterocycles are formed in reactions of aryl halides bearing nucleophilic ortho substituents. - "... 

Preparation of Active Copper and Reaction with Organic Halides to Yield Organocopper Reagents... 

Scheme 57 illustrates an example of this process coupling of the lithio reagent derived from vinyl stannane 237 with epoxide 242 leads to the C-disaccharide derivative 243 in good yield. A double transmetallation to give an organocopper reagent 244 can facilitate the C-glycosylation reaction with allyl halides [80] (Scheme 58). 

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