TetraPh-Tol-BITIOPO: a new atropisomeric 3,3’-bithiophene based phosphine oxide as organocatalyst in Lewis Base-catalyzed Lewis Acid mediated reactions

A new chiral phosphine oxide based on 3,3’-bithiophene scaffold (tetraPh-Tol-BITIOPO) was synthesized, fully characterized and separated into antipodes through chiral HPLC. This new compound was successfully employed as organocatalyst in Lewis base-catalyzed Lewis acid mediated reactions involving trichlorosilyl compounds. The new atropisomeric catalyst was able to promote the allylation of aldehydes with allyltrichlorosilane in up to 98% yield and up to 96% enantiomeric excess (ee), and the direct aldol reaction to afford β-hydroxy ketones and β-hydroxy thioesters, with good chemical yields and modest stereochemical efficiency. Computational studies helped to elucidate and to rationalize the stereochemical outcome of the reactions catalyzed by TetraPh-Tol-BITIOPO, that was found to favour the formation of the isomer with the opposite absolute configuration in comparison with the products obtained with the previously reported 3,3’-bithiophene-based catalyst.