Benzodiazepinoindoles: Chiral Polycyclic Platforms for Various Applications
Tröger bases (TB) are chiral bicyclic compounds with stereogenic N-atoms presenting well-defined V-shape geometry. Numerous applications in supramolecular chemistry, molecular recognition, materials, and catalysis have emerged.1 In our group, routes toward new chiral polycyclic derivatives have been developed using the reactivity of TB 1 with electrophilic carbenes,2. In the present context, those generated by Rh(II)-catalyzed decomposition of N-sulfonyl-1,2,3-triazoles 2 in particular. In one step, after a cascade of five reactions and rearrangements, novel racemic polycyclic benzodiazepinoindoles 3 were synthesized with high diastereoselectivity (d.r.>49:1).3 The corresponding enantiomers can be easily separated by HPLC over chiral stationary phase. Of interest, the aminal functional group can be enantiospecifically removed under specific acidic conditions while maintaining the cup-like geometry of the scaffold.4
Herein, we capitalize on these developments for various applications. For instance, a new class of stable chiral Donor-π-Acceptor (D-π-A) hemicyanine-like fluorophores were straightforwardly prepared under oxidative conditions. Their (chir)optical properties can be further fine-tuned by late-stage cross-coupling reactions.4 On the other hand, a new class of bridged-head stereogenic P-phosphorodiamidite ligands (NidPhos) can be synthesized in good yields. These ligands were obtained with full stereoselectivity (b-form) and they show promising results in enantioselective catalysis.5
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[2] A. Sharma, L. Guénée, J. V. Naubron, J. Lacour, Angew. Chem. Int. Ed. 2011, 50, 3677−3680.
[3] a) A. Bosmani, A. G. Ibáñez, S. Goudedranche, C. Besnard, J. Lacour, Angew. Chem. Int. Ed. 2018, 57, 7151−7155; b) A. Bosmani, A. G. Ibáñez, J. Lacour, Helv. Chim. Acta 2019, 102, e19000.
[4] a) N. Saleh, A. Bosmani, C. Besnard, T. Bürgi, D. Jacquemin, J. Lacour, Org. Lett. 2020, 2, 7599−7603; b) N. Saleh, J. Lacour, SynOpen 2021, 5, 134–137.
[5] N. Saleh et al. Manuscript in preparation.