Modified synthesis of heptahelicene and its resolution into single enantiomers.
Alexandrova, Z.; Sehnal, P.; Stara, I. etc.,
Collection of Czechoslovak Chemical Communications., 71  1256 - 1264 (2006)
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 (-)-(S-a)-(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.