Il'in MV, Safinskaya YV, Polonnikov DA, Novikov AS, Bolotin DS. Chalcogen- and Halogen-Bond-Donating Cyanoborohydrides Provide Imine Hydrogenation.
J Org Chem 2024;
89:2916-2925. [PMID:
38373196 DOI:
10.1021/acs.joc.3c02282]
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Abstract
Sulfonium, selenonium, telluronium, and iodonium cyanoborohydrides have been synthesized, isolated, and fully characterized by various methods, including single-crystal X-ray diffraction (XRD) analysis. The quantum theory of atoms in molecules' analysis based on the XRD data indicated that the hydride···σ-hole short contacts observed in the crystal structures of each compound have a purely noncovalent nature. The telluronium and iodonium cyanoborohydrides provide a significantly higher rate of the model reaction of imine hydrogenation compared with sodium and tetrabutylammonium cyanoborohydrides. Based on the NMR and high-resolution electrospray ionization mass spectrometry data indicating that the reaction progress is accompanied by the cation reduction, a mechanism involving intermediate formation of elusive onium hydrides has been proposed as an alternative to conventional electrophilic activation of the imine moiety by its ligation to the cation's σ-hole.
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