Q87852110
Dotaz
Zobrazit nápovědu
The review deals with the chemistry of helically chiral polyaromatics represented by helicenes. Attention is paid to synthetic methods that can be used for the preparation of helicenes, heterohelicenes and helicene analogues. Of them, the Co- or Ni-catalysed [2+2+2] cycloisomerisation of aromatic triynes to form the helical scaffold, a method developed at the Institute is reviewed. After six decades of helicene chemistry, the interest in these unique aromatic compounds is gradually increasing. As the synthesis of helicenes has recently witnessed a significant progress, their applications in various branches of chemistry, physics and nanoscience can be expected.
- Klíčová slova
- heliceny,
- MeSH
- acetylen chemie MeSH
- katalýza MeSH
- pojmy organické chemie MeSH
- polycyklické sloučeniny * chemie MeSH
- stereoizomerie * MeSH
- vztahy mezi strukturou a aktivitou * MeSH
- Publikační typ
- práce podpořená grantem MeSH
A series of diverse aromatic azadienetriyne and azatriynes was synthesised. These compounds were subjected to transition metal-mediated [2+2+2] cycloisomerisation to form pentacyclic or hexacyclic helically chiral azahelicene or azahelicene-like structures mostly in moderate yields. Introducing stereogenic centre(s) into selected azatriynes, cyclisation proceeded in a stereoselective fashion providing aza[5]helicenes or aza[6]helicene-like compounds in up to a 100:0 diastereomeric ratio. Gibbs energy differences between corresponding pairs of diastereomers (calculated at the DFT(B3LYP)/TZV+P level) were in good agreement with the experimental data and allowed for the prediction of the stereochemical outcome of the reaction. This study presents for the first time asymmetric synthesis of azahelicene derivatives in high optical purities.
By means of selective deuterium labeling of 1-aza[6]helicene combined with resolution of the enantiomers, chiral discrimination in silver(I)-bound dimers of the type [LAgL']+ is probed by electrospray mass spectrometry. The analysis of the results reveals a pronounced preference for the formation of homochiral dimers (P,P and M,M, respectively) over the statistically preferred heterochiral variant (P,M), which is fully consistent with previous data about the formation of homochiral dimers in the condensed phase. Further, competitive experiments with mixtures of 1- and 2-aza[6]helicene suggest a largely preferred coordination of 1-aza[6]helicene to the silver(I) cation.
