Novel route to enantiopure 2,2′-diaryl-1,1′-binaphthalenes by stereoconservative Suzuki arylation at positions 2 and 2′

The Suzuki arylation of enantiopure 2,2'-diiodo-1,1'- binaphthalene affords the 2,2'-diarylated products in considerable yields ( up to 52%), however, significantly racemized. The reversed-polarity approach, using novel enantiopure 1,1'-binaphthalene-2,2'-diyldiboronic acid, prepared either by resolution or by stereoconservative boronation, allowed, after optimization of coupling conditions, to obtain the model 2,2'-ditolylated product in good yield (56%) as well, but in addition, without impairing of enantiomeric purity (i.e. stereoconservatively). The developed synthetic approach was found to be an expedient method for the synthesis of enantiopure 2,2'-diaryl-1,1'-binaphthalenes, especially for those with electron-neutral and electron-deficient poor aryl groups. Observing that the diboronic acid decomposes by hydrodeboronation under the reaction conditions, 2-aryl-1,1'-binaphthalenes were isolated as the main products from the reaction with less reactive electron-rich aryl iodides.