| Abstract
| - Whereas the direct reduction of aryl triflates affordsmainly phenols and some arenes, the presenceof a catalytic amount of palladium or nickel results in the formationof biaryls. The homocouplingis performed in the presence of an electron source, either a cathode orzinc powder. A judiciouschoice of the metal (nickel or palladium), the ligand (monodentate orbidentate phosphine), andthe reduction process (electrochemical or chemical) allows thesynthesis of functional symmetricalbiaryls. Nickel and palladium complexes ligated by bidentateligands such as NiCl2(dppf) andPd(OAc)2 + 1 BINAP are very efficient for thehomocoupling of 1-naphthyl triflate, since the dimerwas obtained in almost quantitative yield. However, thehomocoupling is sensitive to sterichindrance, excluding for the moment the synthesis of atropisomers.The homocoupling proceedsvia an activation of the C−O bond of the aryl triflate bya palladium(0) (or a nickel(0)) complex,providing an intermediate arylpalladium(II) (or nickel(II))complex that after activation by electrontransfer affords a new complex able to undergo a second oxidativeaddition with the aryl triflates.
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