Efficient synthesis of P-chirogenic compounds enabled by chiral selenide-catalyzed enantioselective electrophilic aromatic halogenation

Abstract

P-chirogenic compounds have been applied in different fields, especially in asymmetric catalysis as ligands and organocatalysts. However, broader applicability has been severely restricted by the lack of efficient synthetic methods. Consequently, developing efficient methods to access these compounds is of high synthetic value. Herein, we report a convenient, efficient, and unprecedented pathway to construct valuable P-chirogenic compounds via chiral selenide-catalyzed enantioselective electrophilic aromatic halogenation. Using a new chiral bifunctional selenide as the catalyst, a variety of bis(2-hydro-xyaryl) aryl phosphine oxides were efficiently converted to the corresponding chlorinated and brominated P-chirogenic compounds with good to excellent enantioselectivities. By slightly adjusting the catalyst and solvent, this method is also able to prepare chiral alkyl diaryl phosphine oxides and diaryl phosphinates. Furthermore, control experiments revealed the decomposition pathways of catalysts and the possible reasons why chiral selenide catalyst was more effective than chiral sulfide catalyst. The effect of hydrogen bonding was studied, and the reason why the chlorination took place on the various aromatic rings was elucidated when the substrates were switched from triaryl phosphine oxides to alkyl diaryl phosphine oxides and diaryl phosphinates.(Figure presented)