Coupling of 3,8-dibromo-1,10-phenanthroline with 3,5-diethynylheptyloxybenzene: A Suzuki/miyaura vs. a Sonogashira Perspective
We report a new application of the Suzuki-Miyaura reaction whereas two bifunctional reactants, 3,8-dibromo-1,10-phenanthroline and 3,5-diethynylheptyloxylbenzene (9), yield 3,8-bis(3-ethynyl-5-heptyloxyphenylethynyl)-1,10-phenanthroline (2) efficiently (74% yield) without polymerization. This was achieved by reacting a stoichiometric amount of 9 and (Me3Si)2NLi to obtain quantitatively the monoacetylide anion of 9 (10). The latter was activated with B-methoxy-9-BBN and reacted in analogy to the alkynyl copper complex of a Sonogashira route. However, in the Sonogashira reaction, the alkynyl copper complex is present in small equilibrium concentrations and polymerization takes place even when reagents are mixed slowly. Actually the Sonogashira route gave no desired product 2, as the latter polymerizes easily via homo-coupling in the presence of air and Cu(I).
J. Yang et al., "Coupling of 3,8-dibromo-1,10-phenanthroline with 3,5-diethynylheptyloxybenzene: A Suzuki/miyaura vs. a Sonogashira Perspective," Synthetic Communications, Taylor & Francis, Sep 2003.
The definitive version is available at http://dx.doi.org/10.1081/SCC-120023989
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