Cationic hetero[6]helicenes
mlns="" xmlns:w="http://www.wiley.com/namespaces/wiley" id="chir22579-eo-0001">mol">1+,
mlns="" xmlns:w="http://www.wiley.com/namespaces/wiley" id="chir22579-eo-0002">mol">2+ and
mlns="" xmlns:w="http://www.wiley.com/namespaces/wiley" id="chir22579-eo-0003">mol">3+ have been recently disclosed. Herein we report on their enantio
meric separation using high-perfor
mance
m6">liquid chromatography. Separation of the antipodes can be achieved in preparative scale on neutral adducts with Chiralcel OD-I or Chiralpak ID CSP. Selectivity factors of 1.90, 1.67, and 1.96 were obtained for
mlns="" xmlns:w="http://www.wiley.com/namespaces/wiley" id="chir22579-eo-0007">mol">1-H,
mlns="" xmlns:w="http://www.wiley.com/namespaces/wiley" id="chir22579-eo-0008">mol">2-H, and
mlns="" xmlns:w="http://www.wiley.com/namespaces/wiley" id="chir22579-eo-0009">mol">3-H, respectively. Separation can also be perfor
med on the carbeniu
m ions on regular Chiralpak IA CSP using water-containing eluents, thus allowing for enantio
meric purity deter
minations in aqueous environ
ments. Resolution of neutral and cationic helicenes is also achieved on
more recently developed LARIHC colu
mns. The versatility of the cyclofructan phases allows for baseline separations for both cases and their loading capabilities are de
monstrated. Finally, the configurational stability of
mol">1+,
mol">2+, and
mol">3+ was
measured. For each replace
ment of an oxygen ato
m by an a
mino group, the
m4">racemization barrier increases significantly (Δ
m>Gm>
‡ = 29.8, 36.3 and >37 kcal
mol
-1 for
mol">1+,
mol">2+, and
mol">3+ respectively).
m>Chirality 28:282–289, 2016m>.