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A Highly Active Bifunctional Iridium Complex with an Alcohol/Alkoxide‐Tethered N‐Heterocyclic Carbene for Alkylation of Amines with Alcohols
Author(s) -
Bartoszewicz Agnieszka,
Marcos Rocío,
Sahoo Suman,
Inge A. Ken,
Zou Xiaodong,
MartínMatute Belén
Publication year - 2012
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.201201845
Subject(s) - chemistry , iridium , alkylation , carbene , bifunctional , alcohol , electrophile , medicinal chemistry , reactivity (psychology) , denticity , deprotonation , catalysis , ketene , amine gas treating , ether , alkoxide , organic chemistry , polymer chemistry , crystal structure , medicine , ion , alternative medicine , pathology
A series of new iridium(III) complexes containing bidentate N‐heterocyclic carbenes (NHC) functionalized with an alcohol or ether group (NHCOR, R=H, Me) were prepared. The complexes catalyzed the alkylation of anilines with alcohols as latent electrophiles. In particular, biscationic Ir III complexes of the type [Cp*(NHC‐OH)Ir(MeCN)] 2+ 2[BF 4 − ] afforded higher‐order amine products with very high efficiency; up to >99 % yield using a 1:1 ratio of reactants and 1–2.5 mol % of Ir, in short reaction times (2–16 h) and under base‐free conditions. Quantitative yields were also obtained at 50 °C, although longer reaction times (48–60 h) were needed. A large variety of aromatic amines have been alkylated with primary and secondary alcohols. The reactivity of structurally related iridium(III) complexes was also compared to obtain insights into the mechanism and into the structure of possible catalytic intermediates. The Ir III complexes were stable towards oxygen and moisture, and were characterized by NMR, HRMS, single‐crystal X‐ray diffraction, and elemental analyses.