Synthesis, Chiral Resolution, and Absolute Configuration of Functionalized Tröger’s Base Derivatives: Part II

Abstract

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.

Diastereoselective Self‐Assembly of a Neutral Dinuclear Double‐Stranded Zinc(II) Helicate via Narcissistic Self‐Sorting

“…Interestingly, the subcomponent self‐assembly approach proved to be superior in this case as it gave rise to a pure product, whereas the self‐assembly approach starting from enantiomerically pure ( R , R )‐H 2 ‐ 1 or ( S , S )‐H 2 ‐ 1 only gave rise to the desired aggregate being still contaminated by some trace amounts (<5 % as revealed by NMR spectroscopy) of the free ligand which could not be removed by chromatography . To get to the enantiomerically pure helicates one should therefore follow the subcomponent self‐assembly approach starting from enantiomerically pure 2 which can also be obtained from chiral resolution of Fmoc‐protected racemic material by HPLC on a chiral stationary ( S , S )‐Whelk‐O1 phase …”

Synthesis, Chiral Resolution, and Absolute Configuration of Dissymmetric 4,12‐Difunctionalized [2.2]Paracyclophanes

“…With our experience in HPLC‐based resolutions,9e,9i we wanted to employ this technique for the direct separation of racemic 4 , 5 , and 7 . In fact, all these compounds could be resolved in a very efficient manner, both on an analytical and on a semipreparative scale, by using a chiral CHIRALPAK IA stationary phase and mixtures of n ‐hexane and simple alcohols such as ethanol or 2‐propanol as eluent, as illustrated for 4 in Figure 1.…”

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“…Amongst halogenated TBAs, those carry bromo substituents are known as the best substrate for a variety of reactions including the amination of halogen carrying TBAs [35]. The bromo substituent can be used in various nucleophilic substitution [36] and cross-coupling reactions [29,30,32,[37][38][39][40]. Moreover, bromo-carrying TBAs can be reduced back to unsubstituted TBAs, e.g.…”