Diastereospecific intramolecular Ullmann couplings: unique chiral auxiliary for the preparation of 3,3'-disubstituted MeO-BIPHEP derivatives.
[reaction: see text] A chiral auxiliary is described that provides only one diastereomer during intramolecular Ullmann couplings. Treatment of five Ullmann coupling precursors with Cu powder in DMF at 115 degrees C provides 2,2',3,3',6,6'-hexasubstituted 1,1'-biphenyls as single diastereomers in yields ranging from 66% to 91%.
Department of Chemistry, University of Calgary, Calgary, AB, Canada.
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Gorobets
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McDonald
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Keay