Suzuki arylation at positions 2 and 2′ of 1,1′-binaphthyls: stereochemical result depending on the sense of polarity of substrates

The first preparation of enantiomerically pure 1,1′-binaphthyl-2,2′-diboronic acid (by resolution) is reported. Optimization of the cross-coupling conditions was found to be crucial to achieve good yields in Suzuki arylation in approaches from both 2,2′-diiodide or 2,2′-diboronic acid (52–56%, with model p-tolyl reagents). Stereochemical results in these reactions were dramatically different: almost complete racemization starting from the 2,2′-diiodide versus complete conservation of stereogenic information from the 2,2′-diboronic acid. This novel synthetic approach, a stereoconservative Suzuki arylation of the diboronic acid, should be a valuable method for the synthesis of a new group of 2,2′-diarylated (including functionalized) binaphthyl derivatives.