Novel enantiomerically pure tetramethylbithiophene
diphosphine oxides (tetraMe-BITIOPO)
featuring differently substituted aromatic rings at the
phosphorous atoms were synthesized, fully characterized
and isolated in enantiomerically pure form. The new
Lewis bases were tested as organocatalysts in two
different reactions involving trichlorosilyl compounds.
The introduction of electron donating substituents on the
aromatic rings connected to the phosphine oxide groups
positively affected the chemical and stereochemical
catalytic efficiency of these ligands. The new catalysts
were able to promote the allylation of aldehydes with
allyltrichlorosilane in up to 76% yield and up to 86%
enantiomeric excess (ee), and the direct aldol reaction to
afford β-hydroxy ketones in high diastereoselectivity (up
to 88:12 anti:syn ratio) and up to 72% ee.