Aryltrialkylstannanes homo-couplings

In similar manner, hexaalkyldistannanes allow the homo-coupling reactions of aryl iodides, bromides [104] and triflates [105] to the symmetrical biaryls. First, the aryltrialkylstannane is generated by reaction of the aryl halides with Me6Sn2 or -BugSn2, followed by the in situ Stille reaction with an excess of electrophilic reactant, since both reactions are catalysted by the same complexes and proceed at comparable reaction rates. For instance, 2-naphthyl triflate (165) was coupled to 2,2 -binaphthalene (166) in 69% yield [105], respectively, Scheme 22. 

Note Copper(lI) nitrate is also efficient reagent for the homo-coupling reaction of aryltrialkylstannanes at molar ratio ArSnR3 Cu(N03)2 = 1 5 to give high yields of symmetrical biaryls in dry DMF or THF [27,28]. 

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