Access to Chiral Silicon Centers for Application to Circularly Polarized Luminescence Materials

Asymmetric
arylation of secondary silanes catalyzed by a Pd-chiral
phosphoramidite complex was developed for application to low-molecular-weight
circularly polarized luminescence (CPL) materials. The asymmetric
arylation provided a convenient, efficient synthetic method for a
variety of chiral tertiary silanes (2–21), which were key intermediates for preparing the quaternary silicon
center. A stepwise, one-pot procedure was used to transform the appropriate
aryl iodide to the quaternary silane (22) with good yield
and enantioselectivity. Among compounds synthesized in this work,
four optically pure tertiary silanes (18–21) were selected to investigate the relationship between
the structure and optical properties. Optically pure (S,S)-21 displayed the highest CPL emission with a high
fluorescence quantum yield (glum: +0.008,
ΦF: 0.42). This simple molecular design provides
new strategies for developing small organic CPL dyes.