Starting from the optically pure [6]helicene-like alcohol (P,3S)-3-methyl-4-(4-methylphenyl)-1, 3,6,7-tetrahydrobenzo-[c]benzo [5,6]phenanthro [4,3-e]oxepin-14-ol, four helical phosphites were prepared from the corresponding chlorophosphites. These ligands containing parent or substituted 1,3,2-dioxaphospholan-2-yl or dibenzo [d,f][1,3,2]dioxaphosphepin-6-yl moieties were applied to the asymmetric hydroformylation of terminal alkenes catalyzed by Rh(acac)(CO) 2 and the asymmetric allylic amination of cinnamyl-type carbonates catalyzed by [Ir(cod)Cl] 2 . The helical phosphite containing the dibenzo [d,f][1,3,2]dioxaphosphepin-6-yl group was most successful in the asymmetric hydroformylation of

Diastereoselective CoI-mediated [2 + 2 + 2] cycloisomerization of CH(3)O-substituted optically pure aromatic triynes to obtain nonracemic functionalized helicene-like compounds (comprising a penta-, hexa-, and heptacyclic helical scaffold) was studied. The stereochemical outcome of the reaction at 140 degrees C using CpCo(CO)(2) was controlled by thermodynamic factors yielding diastereomeric ratios up to 91:9. Using CpCo(ethylene)(2) at room temperature, a kinetic control took place leading to the loss of stereoselectivity. Barriers to epimerization for selected helicene-like compounds were measured indicating their lower configurational stability in comparison to the parent carbohelicenes. Free energy differences between corresponding pairs of diastereomers (calculated at the DFT B3LYP/TZV+P level) were in excellent agreement with the experimental data and allowed for the prediction of the stereochemical outcome of the reaction. An optically pure hexacyclic helicene-like alcohol was prepared on a multigram scale. Its X-ray structure confirmed the previous helicity assignments being based on (1)H-(1)H correlations in ROESY (1)H NMR spectra.

Abstract2‐Hydroxy‐ and 2,15‐dihydroxyhexahelicene were synthesised from simple benzene and naphthalene building blocks by intramolecular CoI‐ or Ni0‐catalysed [2+2+2] cycloisomerisation of CH3O‐substituted aromatic triynes. This approach avoids vexing photodehydrocyclisation of stilbene‐type precursors, providing thus a useful alternative to classical procedures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A modular synthesis of a series of methoxy substituted optically pure aromatic triynes (-)-(S)-5-9 and (-)-(R)-10 is presented. It relies on key operations such as substitution of benzylic bromine with an alkoxy group and aryl-alkyne coupling reaction to combine appropriate methoxy substituted benzene/naphthalene building blocks and chiral alkynol synthons such as (-)-(2S)-but-3-yn-2-ol and (-)-(1R)-1-phenylprop-2-yn-1-ol. The triyne molecules comprise a diphenylacetylene, 1-(phenylethynyl)naphthalene or 1,1'-ethyne-1,2-diyldinaphthalene core unit. They are intended to serve as [2+2+2] cyclisation precursors of methoxy substituted nonracemic helicene-like compounds with a penta-, hexa- and heptacyclic helical scaffold.