Helda

Helsingin yliopisto

Helsingfors universitet

University of Helsinki

Browsing by Subject "FRUSTRATED LEWIS PAIR"

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Borane adducts of punicine and of its dehydroxy derivatives (pyridinium-1-yl)-2-and 3-phenolates

Otto, Christian F.; Herzberger, Colin; Liu, Ming; Namyslo, Jan C.; Nieger, Martin; Freese, Tyll; Lederle, Felix; Hübner, Eike G.; Schmidt, Andreas (2020)

The natural product punicine (Punica granatum) exists in two tautomeric forms, the cross-conjugated mesomeric betaine 1-(pyridinium-1-yl)-2-hydroxy-phenyl-5-olate and the conjugated mesomeric betaine 1-(pyridinium-1-yl)-5-hydroxy-phenyl-2-olate. Punicine as well as its picoline derivatives reacted with tris(pentafluorophenyl)borane exclusively at the 2'-olate group to form zwitterionic borates. Correspondingly, the 5'-dehydroxy derivate of punicine, the conjugated heterocyclic mesomeric betaine 1-(pyridinium-1-yl)-phenyl-2-olate and its picoline derivatives also gave borates, whereas analogous reactions of the cross-conjugated isomer 2'-dehydroxypunicine [1-(pyridinium-1-yl)-phenyl-3-olatel did not result in the formation of stable adducts. (C) 2020 Elsevier Ltd. All rights reserved.
Catalytic Dehydrogenation of Amine-Boranes using Geminal Phosphino-Boranes

Boom, Devin H. A.; de Boed, Ewoud J. J.; Nicolas, Emmanuel; Nieger, Martin; Ehlers, Andreas W.; Jupp, Andrew R.; Slootweg, J. Chris (2020)

The reaction of the intramolecular frustrated Lewis pair (FLP) tBu2PCH2BPh2 with the amine-boranes NH3·BH3 and Me2NH·BH3 leads to the formation of the corresponding FLP-H2 adducts as well as novel five-membered heterocycles that result from capturing the in situ formed amino-borane by a second equivalent of FLP. The sterically more demanding tBu2PCH2BMes2 does not form such a five-membered heterocycle when reacted with Me2NH·BH3 and its H2 adduct liberates dihydrogen at elevated temperatures, promoting the metal-free catalytic dehydrogenation of amine-boranes.