Seven racemic derivatives of Tröger’s base—the 1,7‐dibromo‐substituted derivative 3, the 2,8‐dibromo‐substituted derivative 4, the 2,8‐diiodo‐substituted derivative 5, the 3,9‐diiodo‐substituted derivative 6, the 4,10‐dibromo‐substituted derivative 7, its singly debrominated analogue 8, and the 2,8‐diamino‐substituted derivative 9 in its Fmoc‐protected form—were synthesized and successfully resolved by (recycling) HPLC on a stationary Whelk‐O1 phase at a semipreparative scale. These are valuable functionalized C2‐symmetric building blocks for further applications. Their absolute configurations were determined by X‐ray crystal structure analysis and/or by comparison of their quantum chemically calculated circular dichroism and UV/Vis spectra with the experimental obtained spectra.
An enantiomerically pure bis(bipyridine) BINOL ligand was synthesized which was functionalized with an iodine substituent in its periphery. Using this halogen function, the ligand was immobilized on a commercially available polystyrene gel via Suzuki cross-coupling. The functionalized gel was found to be effective in the chiral resolution of similar bis(bipyridine) ligands based on a Tröger's base core.
The Diels–Alder cycloaddition reaction of tetracyclone and functionalized, internal aryl acetylenes gave access to a number of bulky atropisomeric biaryls in good to excellent yield. The synthesis is convenient and yields the pure biaryls without tedious work‐up and purification procedures. Exemplarily the atropisomers have been resolved via the diastereomers in an easy and efficient manner to yield the enantiomers.
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