An Axially Chiral 1,1′-Biazulene and Its π-Extended Derivative: Synthesis, Structures and Properties
Chiral organic π-conjugated molecules have been intensively investigated in the fields of chiral electronic materials and devices. Herein we report a new motif for the axially chiral 1,1’-biazulene and its π-extended derivative, in which biphenyl was annulated by electron-rich five membered-ring of azulene moiety. These two compounds were unexpectedly synthesized from 2-terphenyl azulene by stepwise intermolecular and intramolecular oxidative C-H/C-H couplings. X-ray diffraction analysis revealed that the crystals of both compounds contain a pair of enantiomers. Furthermore, the axially chiral 1,1’-biazulene derivatives were successfully separated into enantiomers that exhibited clear mirror-image circular dichroism spectra up to near-infrared region.