selectively substituted to the para-position with respect to their oxygen substituent.
The chiral auxiliary groups were removed using KOH to obtain the enantiopure
dibrominated PHANOL. The reaction with trifluoromethanesulfonic anhydride as
well as MeI affords bis-(para)-pseudo-ortho-type tetrasubstituted [2.2]
paracyclophanes. Optical resolution could also be carried out after the bromination
of the mixture of diastereomers, as shown in Fig. 3.8. This modified route involved a
single bromination step to produce both the diastereomers [37].
Enantiopure bis-(para)-pseudo-meta-tetrasubstituted [2.2]paracyclophane derivatives were successfully synthesized (Fig. 3.9) [38]. The starting material, racemic
4,7,12-tribromo-15-hydroxy[2.2]paracyclophane, was reacted with n-BuLi. First,
the phenol in rac-2 was reacted with n-BuLi to form lithium phenoxide. Then, nBuLi attacked selectively at the corresponding pseudo-meta-position because of the
electronic effect. The optical resolution was achieved by the diastereomer method
using camphanoyl chloride as the chiral auxiliary. The camphanoyl groups could be
removed by saponification, and the obtained 4,15-dibromo-7,12-dihydroxy[2.2]
paracyclophane was converted to (R p )- and (S p )-4,15-dibromo-7,12trifluoromethanesulfonyloxy[2.2]paracyclophanes, for using them as chiral building
blocks.
Fig. 3.6 Optical resolution of 4,7,12,15-tetrasubstituted [2.2]paracyclophane and the
transformation
36
Y. Morisaki
The chiral auxiliary groups were removed using KOH to obtain the enantiopure
dibrominated PHANOL. The reaction with trifluoromethanesulfonic anhydride as
well as MeI affords bis-(para)-pseudo-ortho-type tetrasubstituted [2.2]
paracyclophanes. Optical resolution could also be carried out after the bromination
of the mixture of diastereomers, as shown in Fig. 3.8. This modified route involved a
single bromination step to produce both the diastereomers [37].
Enantiopure bis-(para)-pseudo-meta-tetrasubstituted [2.2]paracyclophane derivatives were successfully synthesized (Fig. 3.9) [38]. The starting material, racemic
4,7,12-tribromo-15-hydroxy[2.2]paracyclophane, was reacted with n-BuLi. First,
the phenol in rac-2 was reacted with n-BuLi to form lithium phenoxide. Then, nBuLi attacked selectively at the corresponding pseudo-meta-position because of the
electronic effect. The optical resolution was achieved by the diastereomer method
using camphanoyl chloride as the chiral auxiliary. The camphanoyl groups could be
removed by saponification, and the obtained 4,15-dibromo-7,12-dihydroxy[2.2]
paracyclophane was converted to (R p )- and (S p )-4,15-dibromo-7,12trifluoromethanesulfonyloxy[2.2]paracyclophanes, for using them as chiral building
blocks.
Fig. 3.6 Optical resolution of 4,7,12,15-tetrasubstituted [2.2]paracyclophane and the
transformation
36
Y. Morisaki