Collect. Czech. Chem. Commun. 2003, 68, 917-930

Synthesis of Helicene Scaffolds via [2+2+2] Cycloisomerization of Aromatic Triynes

Irena G. Stará*, Ivo Starý*, Adrian Kollárovič, Filip Teplý, David Šaman and Pavel Fiedler

Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic


Triynes R-C≡C-CH2CH2-Ar-C≡C-Ar'-CH2CH2-C≡C-R were subjected to Co(I)- or Ni(0)-mediated intramolecular [2+2+2] cycloisomerization to provide corresponding tetrahydropentahelicene, tetrahydrohexahelicene, and tetrahydroheptahelicene in good to moderate yields. The reaction tolerates various substituents at pendant acetylene moieties (R = H, CH3, trimethylsilyl, not triisopropylsilyl) and fluorine in an aromatic part. By contrast, under Rh(I) or Pd(0) catalysis, triyne with the CH2OCH2 tether lost pendant propargyl moieties and an aromatic spiroketal was formed preferentially.

Keywords: Alkynes; Arenes; Cobalt catalysis; Helical chirality; Helicenes; Nickel catalysis; Palladium catalysis; Rhodium catalysis; Spiroketals; Tetrahydrohelicenes; Triyne cyclotrimerization.

References: 40 live references.