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Abstract. An extensive study of the reactivity of organometallic reagents R3M (R3 = I-alkenyl, I-alkynyl, 3-alken-l-yny1, 1,3-alkadiynyl or 1,2-alkadienyl; M = Li, MgCI, ZnCI, Cu, Ag) towards RIRZC=C=CH-X (1) and R'R2C(X)-C=CH (4) is described. High yields of R'R*C=C= =CH-R3 (2) have been obtained by reaction of 1 (X = Br) with R3-M (M = MgCI, ZnCl or Cu,Li+) using Pd[PPh3], as-catalyst. Similarly, pure 2 have been obtained by the Pd[PPh,],--catalyzed reaction of 4 (X = Br, OAc, OS(O)Me, OSO'Me, OP(O)(OEt),) with R3-M (M = MgCl, ZnCI, Zn+ Cu, Cu,Li,, Ag, or AgtLi+). In some reactions with R3-Cu, compounds 4 were converted into 2 in the absence of the palladium catalyst.

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