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Alkali‐Metal‐Mediated Magnesiations of an N‐Heterocyclic Carbene: Normal, Abnormal, and “Paranormal” Reactivity in a Single Tritopic Molecule
Author(s) -
MartínezMartínez Antonio J.,
Fuentes M. Ángeles,
HernánGómez Alberto,
Hevia Eva,
Kennedy Alan R.,
Mulvey Robert E.,
O'Hara Charles T.
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201507586
Subject(s) - carbene , chemistry , amide , bimetallic strip , aryl , ring (chemistry) , metalation , alkali metal , substituent , molecule , stereochemistry , medicinal chemistry , metal , crystallography , alkyl , catalysis , organic chemistry
Herein the sodium alkylmagnesium amide [Na 4 Mg 2 (TMP) 6 ( n Bu) 2 ] (TMP=2,2,6,6‐tetramethylpiperidide), a template base as its deprotonating action is dictated primarily by its 12 atom ring structure, is studied with the common N‐heterocyclic carbene (NHC) IPr [1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]. Remarkably, magnesiation of IPr occurs at the para ‐position of an aryl substituent, sodiation occurs at the abnormal C4 position, and a dative bond occurs between normal C2 and sodium, all within a 20 atom ring structure accommodating two IPr 2− . Studies with different K/Mg and Na/Mg bimetallic bases led to two other magnesiated NHC structures containing two or three IPr − monoanions bound to Mg through abnormal C4 sites. Synergistic in that magnesiation can only work through alkali‐metal mediation, these reactions add magnesium to the small cartel of metals capable of directly metalating a NHC.