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N‐Heterocyclic Carbene Derived 3‐Azabutadiene as a π‐Base in Classic and Frustrated Lewis Pair Chemistry
Author(s) -
Kim Youngsuk,
Liu Liu Leo,
Stephan Douglas W.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201901609
Subject(s) - chemistry , carbene , lewis acids and bases , delocalized electron , adduct , isocyanide , nucleophile , moiety , frustrated lewis pair , medicinal chemistry , single bond , natural bond orbital , stereochemistry , crystallography , computational chemistry , density functional theory , organic chemistry , alkyl , catalysis
N‐Heterocyclic carbene (NHC) derived 3‐azabutadienes 1 and 2 have been prepared by a single‐step reaction of the corresponding NHC with cyclohexyl isocyanide. Compound 1 features π‐basic, delocalized nucleophilic sites over the 3‐azabutadiene moiety, therefore allowing for coordinating with small Lewis acids, such as AlCl 3 , GaCl 3 , and Me 2 SAuCl, to form diverse classic Lewis adducts 3 – 5 . Combination of 1 with B(C 6 F 5 ) 3 or [Ph 3 C][B(C 6 F 5 ) 4 ] resulted in single‐electron transfer and the obtained radical cation was detected by EPR. In addition, a frustrated Lewis pair comprised of the π‐basic 1 and BPh 3 effects the splitting of the O−H bond of phenol and the N−H bond of imidazole to give 7 and 8 , respectively. An intrinsic bond orbital (IBO) analysis of the pathway leading to 8 showcases the transformation of the delocalized π‐electrons of 1 to a newly formed C−H localized σ‐bond.