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Computational-aided Design of Neutral Chiral Bidentate Tellurium-Triazoles for Enantioselective Chalcogen-Bonding Catalysis
This work reports a computational-aided design driven approach towards chiral chalcogen-bond donor structures able to accomplish the still unprecedented, highly challenging asymmetric chalcogen-bonding catalysis. Optimisation of the chiral central backbone in rather simple bistriazole-bistelluride-based structures to effect a bidentate binding to Lewis basic substrates was performed, leading to the identification of (R,R)-1,3-diamino cyclohexane moiety as appropriate chiral spacer. While no binding was observed for other chiral central backbones, a moderate affinity to chloride anion as model substrate was recorded for the optimised neutral, bidentate system (Ka ~50-60 M-1 in THF-d8), for which key binding features were further revealed upon computational analysis on the corresponding catalyst-chloride complex. Hence, a chiral induction using chalcogen-bond as main activation was achieved for the first time, reaching enantioselectivities of up to 11:89 e.r. (78% ee) in the chosen test anion-binding benchmark Reissert-type reaction of (iso)quinolines.
