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Enantioselective Protonation: Hydrophosphinylation of 1,1‐Vinyl Azaheterocycle N ‐Oxides Catalyzed by Chiral Bis(guanidino)iminophosphorane Organosuperbase
Author(s) -
Das Saikat,
Hu Qiupeng,
Kondoh Azusa,
Terada Masahiro
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202012492
Subject(s) - enantioselective synthesis , protonation , chemistry , phosphine oxide , enantiomer , oxide , catalysis , medicinal chemistry , conjugate , organic chemistry , phosphine , ion , mathematical analysis , mathematics
Enantioselective protonation by hydrophosphinylation of diarylphosphine oxides with 2‐vinyl azaheterocycle N ‐oxide derivatives was demonstrated using chiral bis(guanidino)iminophosphorane as the higher‐order organosuperbase catalyst. It was confirmed by several control experiments that a chiral weak conjugate acid of the chiral bis(guanidino)iminophosphorane, instead of achiral diarylphosphine oxides, directly functioned as the proton source to afford the corresponding product in a highly enantioselective manner in most cases. Enantioselective protonation by a weak conjugate acid generated from the higher‐order organosuperbase would broaden the scope of enantioselective reaction systems because of utilization of a range of less acidic pronucleophiles. This method is highlighted by the valuable synthesis of a series of chiral P,N‐ligands for chiral metal complexes through the reduction of phosphine oxide and N ‐oxide units of the corresponding product without loss of enantiomeric purity.