Stereospecific Synthesis of Enantiopure Helicene Containing a Seven‐Membered Ring and Helicene by Acid‐Promoted Stepwise Alkyne Annulations of Doubly Axial‐Chiral Precursors
Enantiopure (>99 % ee) helicene with a seven-membered ring and carbohelicene have been simultaneously and quantitatively (>99 %) synthesized with opposite helicity from optically pure doubly axial-chiral cyclization precursors. The stepwise acid-promoted intramolecular alkyne annulations involved a complete axial-to-helical chirality transfer, which led to the helicity being fully stereo-controlled.
Enantiopure helicene containing an embedded seven-membered ring and carbohelicene (>99 % ee) with opposite helicity were simultaneously and quantitatively (>99 %) synthesized with a perfect stereospecificity through stepwise acid-promoted intramolecular alkyne annulations of doubly axial-chiral cyclization precursors. The helical handedness of the - and helicenes was fully stereocontrolled by the doubly axial chirality of the precursors as a result of complete axial-to-helical chirality transfer. The cyclizations proceeded in a stepwise manner; the first six-membered ring formation was followed by the kinetically controlled seven- or six-membered ring formation with or without helix-inversion of a helicene intermediate generated during the first cyclization step, thus quantitatively producing enantiopure circularly polarized luminescent - and helicenes with opposite helicity.Zum Volltext
Überprüfung Ihres Anmeldestatus ...
Wenn Sie ein registrierter Benutzer sind, zeigen wir in Kürze den vollständigen Artikel.