Collect. Czech. Chem. Commun. 2006, 71, 1256-1264

Modified Synthesis of Heptahelicene and Its Resolution Into Single Enantiomers

Zuzana Alexandrováa, Petr Sehnala, Irena G. Staráa,*, Ivo Starýa,*, David Šamana, Stephen G. Urquhartb and Edwige Oterob

a Center for Biomolecules and Complex Molecular Systems, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
b Department of Chemistry, University of Saskatchewan, Saskatoon SK S7N 5C9, Canada


A practical synthesis of racemic heptahelicene has been develeped being based on key [2+2+2] cycloisomerization of bis[2-(but-3-yn-1-yl)-1-naphthyl]acetylene under CpCo(CO)2/PPh3 or CpCo(C2H4)2 catalysis. The application of the Ni(cod)2 catalyst with (-)-(Sa)-(2'-methoxy-1,1'-binaphthalen-2-yl)diphenylphosphane resulted in enantioselective triyne cyclization to provide (+)-7,8,11,12-tetrahydroheptahelicene in 40% ee. Optically pure (-)-(M)- and optically highly enriched (+)-(P)-heptahelicene were obtained on a milligram scale by resolution of racemate by chiral HPLC on a semipreparative Whelk-O1 column.

Keywords: Helicenes; Heptahelicene; Alkynes; Triynes; Cycliosomerization; Cobalt catalysis; Nickel catalysis; Enantioselective catalysis; Racemate resolution; Chiral HPLC.

References: 39 live references.