Organocoppers exchange with

Diorganocuprates couple readily with vinylic halides and have been employed in the synthesis of some natural products, e.g., fulvoplumieren and Cecropia juvenile hormone (26, 27, 62, 63). Copper-halogen exchange can occur simultaneously 174, 309). Successful coupling reactions of organocopper compounds with vinylic halides are listed in Table VIII. 

Michael additions [112] and other reactions typical of organocopper species can also be performed with silylcopper reagents such as TBDMSCu, prepared by Sn/Cu exchange [113] between Me3SnSiMc2(tBu) and Bu(Th)CuLi LiCN (Th = 2-thienyl) (Scheme 2.53) [113, 114]. 

Recently, the direct transformation of allyl- 206272 and aryl tellurides 209273 into the corresponding organocopper species 207 and 210 by tellurium-copper exchange was described. The resulting allyl 207 or aryl cuprates 210 were captured by coupling with vinyl triflates 208272 or by 1,4-addition to enones 211,273 respectively (Scheme 112). 

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. 

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