Helicity control in the synthesis of helicenes and related compounds.
Stary, I.; Stara, I.; Alexandrova, Z. etc.,
Pure and Applied Chemistry, 78  495 - 499 (2006)
Asymmetric synthesis of helicenes and their congeners has been demonstrated to rely either on enantioselective Ni-0/PR3*-catalyzed [2+2+2] cycloisomerization of triynes or on diastereoselective Co-I-catalyzed [2+2+2] cycloisomerization of chiral triynes. The former approach providing tetrahydrohelicenes in a nonracemic form requires further development as moderate enantioselectivities (up to 54 % ee) have so far been achieved under kinetic control. The latter approach affording helicene-like structures in a diastereomerically enriched form allows for reaching good to excellent diastereoselectivities (up to 100:0) under thermodynamic control.