Comparison between PdCl2(PPh3)2- and NiCl2(PPh3)2-Catalyzed Crosscoupling of Aryl Halides by Intramolecularly Stabilized Dialkylaluminum Reagents

Dmitri Gelman; Gerhard Höhne; Herbert Schumann; Jochanan Blum

doi:10.1055/s-2001-12364

Synthesis 2001; 2001(4): 0591-0594
DOI: 10.1055/s-2001-12364

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Comparison between PdCl₂(PPh₃)₂- and NiCl₂(PPh₃)₂-Catalyzed Crosscoupling of Aryl Halides by Intramolecularly Stabilized Dialkylaluminum Reagents

Dmitri Gelman^* , Gerhard Höhne, Herbert Schumann, Jochanan Blum

^*Department of Organic Chemistry, Hebrew University, Jerusalem 91904, Israel; Fax + 972(2)6 51 38 32; E-mail: jblum@chem.ch.huji.ac.il

Abstract

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The catalytic activities of PdCl₂(PPh₃)₂ and of NiCl₂(PPh₃)₂ in cross coupling of some chloro- and bromoarenes with intramolecularly stabilized aluminum complexes [R₂AlOCH₂CH₂NMe₂]₂ (R = Ph, PhC≡C, PhCH₂, Et and i-Bu) are compared. The palladium catalyst promotes clean cross-alkylation of aryl bromides indifferently to the nature of the R groups of the alkylating reagents, but does not activate aryl chlorides. The nickel complex catalyzes cross-alkylation of both aryl bromides and chlorides, provided the R groups do not have β-hydrogen atoms. Diethyl- and diisobutylaluminum complexes that disproportionate in the presence of the nickel catalyst cause substantial hydrogenolysis of the aryl halides.

aluminum complexes - aryl halides - cross coupling - nickel catalyst - palladium catalyst

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