trisubstituted [2.2]paracyclophane (Fig. 3.5) by diastereomer methods [34]. The
optical resolution of 4,7,12,15-tetrasubstituted [2.2]paracyclophane was achieved
in 2014 [35], as shown in Fig. 3.6. The racemate 4,7,12-tribromo-15-hydroxy[2.2]
paracyclophane was synthesized from the corresponding tetrabromide, and the
reaction with (1S,4R)-(-)-camphanic chloride afforded the diastereomers
(R p ,1S,4R)- and (S p ,1S,4R)-isomers. The diastereomers could be separated in gram
scale using the simple silica gel column chromatography, and the diastereomer ratios
were over 99.5%. The hydroxy group was converted to the trifluoromethanesulfonyl
group, which is an active site for the Pd-catalyzed cross-coupling, in addition to the
bromo groups.
Optical resolution of rac-PHANOL [26] was applied to produce enantiopure
bis-(para)-pseudo-ortho-4,7,12,15-tetrasubstituted [2.2]paracyclophanes [36], as
shown in Fig. 3.7. The obtained diastereomers were reacted with bromine, in the
presence of iron, to afford bis-(para)-pseudo-ortho-4,7,12,15-tetrasubstituted [2.2]
paracyclophanes (R p ,1S,4R)- and (S p ,1S,4R)-isomers, wherein bromine was
Fig. 3.5 Optical resolutions of bis-(ortho)-pseudo-meta-4,5,15,16-tetrasubstituted [2.2]
paracyclophane and 4,5,15-trisubstituted [2.2]paracyclophane
3 Circularly Polarized Luminescence from Planar Chiral Compounds Based on. . .
35