2018 Volume 91 Issue 2 Pages 187-194
The catalytic enantioselective synthesis of planar chiral cyclophanes has been achieved by two types of transition-metal catalysis: (1) enantioselective construction of aromatic rings by transition-metal-catalyzed [2+2+2] cycloaddition reactions; (2) enantioselective construction of ansa chains by transition-metal-catalyzed coupling reactions. The former approach has been achieved by the cationic rhodium(I)/H8-BINAP complex-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of triynes, which afforded planar chiral dioxa–metacyclophanes with high ee values, although the yields were low. Planar chiral carba–paracyclophanes could also be synthesized with high yields and ee values by the cationic rhodium(I)/BDPP complex-catalyzed enantioselective intermolecular [2+2+2] cycloaddition of cyclic diynes with monoynes. On the other hand, the latter approach was achieved by the cationic rhodium(I)/BINAPHANE or palladium(II)/BINAP complex-catalyzed double C–S bond formation between dithiols and 1,4-bis(bromomethyl)benzenes, which afforded planar chiral dithia–paracyclophanes and dithia[3.3]paracyclophanes with varying yields and ee values.
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