TY - JOUR
TI - A Versatile Tripodal Cu(I) Reagent for C–N Bond Construction via Nitrene-Transfer Chemistry: Catalytic Perspectives and Mechanistic Insights on C–H Aminations/Amidinations and Olefin Aziridinations
AU - Vivek Bagchi
AU - Patrina Paraskevopoulou
AU - Purak Das
AU - Lingyu Chi
AU - Qiuwen Wang
AU - Amitava Choudhury
AU - Jennifer S. Mathieson
AU - Leroy Cronin
AU - Daniel B. Pardue
AU - Thomas R. Cundari
AU - George Mitrikas
AU - Yiannis Sanakis
AU - Pericles Stavropoulos
JO - Journal of the American Chemical Society
PY - 2014
VL - 136
TODO - 32
SP - 11362--11381
PB - American Chemical Society (ACS)
SN - 0002-7863, 1520-5126
TODO - 10.1021/ja503869j
TODO - null
TODO - A Cu-I catalyst (1), supported by a framework of strongly basic
guanidinato moieties, mediates nitrene-transfer from PhI=NR sources to a
wide variety of aliphatic hydrocarbons (C-H amination or amidination in
the presence of nitriles) and olefins (aziridination). Product profiles
are consistent with a stepwise rather than concerted C-N bond formation.
Mechanistic investigations with the aid of Hammett plots, kinetic
isotope effects, labeled stereochemical probes, and radical traps and
clocks allow us to conclude that carboradical intermediates play a major
role and are generated by hydrogen-atom abstraction from substrate C-H
bonds or initial nitrene-addition to one of the olefinic carbons.
Subsequent processes include solvent-caged radical recombination to
afford the major amination and aziridination products but also
one-electron oxidation of diffusively free carboradicals to generate
amidination products due to carbocation participation. Analyses of
metal- and ligand-centered events by variable temperature electrospray
mass spectrometry, cyclic voltammetry, and electron paramagnetic
resonance spectroscopy, coupled with computational studies, indicate
that an active, but still elusive, copper-nitrene (S = 1) intermediate
initially abstracts a hydrogen atom from, or adds nitrene to, C-H and
C=C bonds, respectively, followed by a spin flip and radical rebound to
afford intra- and intermolecular C-N containing products.
ER -