Atroposelective Synthesis of 2,2′-Bis(arylamino)-1,1′-biaryls by Oxidative Iron(III)- and Phosphoric Acid-Catalyzed C-C Coupling of Diarylamines

We describe an iron-catalyzed asymmetric oxidative C-C coupling of diarylamines which proceeds at room temperature with air as final oxidant. Using hexadecafluorophthalocyanine-iron(II) as catalyst in the presence of catalytic amounts of an axially chiral biarylphosphoric acid, the resulting chiral 2,2 '-diamino-1,1 '-biaryls are obtained in up to 90 % ee as confirmed by chiral HPLC. A detailed mechanism has been proposed with a radical cation-chiral phosphate ion pair as key intermediate leading to the observed asymmetric induction.

Automated summary

We report an iron-catalyzed asymmetric oxidative C-C coupling reaction which takes place at room temperature using air as the final oxidant. By using hexadecafluorophthalocyanine-iron(II) as the catalyst and the presence of catalytic amounts of an axially chiral biarylphosphoric acid, chiral 2,2'-diamino-1,1'-biaryls with up to 90% enantiomeric excess (ee) were obtained as confirmed by chiral HPLC analysis. A detailed mechanism involving a radical cation-chiral phosphate ion pair as the key intermediate leading to the observed asymmetric induction is proposed.