Pure and Applied Chemistry

Abstract: Asymmetric synthesis of helicenes and their congeners has been demonstrated to rely either on enantioselective Ni⁰/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.