Organic Chemistry Frontiers,
Journal Year:
2020,
Volume and Issue:
7(15), P. 2047 - 2054
Published: Jan. 1, 2020
The
mechanism
of
the
Cu(i)-catalyzed
reductive
A3-coupling
reaction
terminal
alkynes
with
aldehydes
and
3-pyrroline
for
synthesis
ofE-allylic
amines
has
been
studied
by
DFT
calculations.
Science,
Journal Year:
2023,
Volume and Issue:
381(6662), P. 1072 - 1079
Published: Sept. 7, 2023
The
step
that
cleaves
the
carbon-halogen
bond
in
copper-catalyzed
cross-coupling
reactions
remains
ill
defined
because
of
multiple
redox
manifolds
available
to
copper
and
instability
high-valent
product
formed.
We
report
oxidative
addition
α-haloacetonitrile
ionic
neutral
copper(I)
complexes
form
previously
elusive
but
here
fully
characterized
copper(III)
complexes.
stability
these
stems
from
strong
Cu−CF
3
high
barrier
for
C(
CF
)−C(
CH
2
CN
)
bond-forming
reductive
elimination.
mechanistic
studies
we
performed
suggest
proceeds
by
means
two
different
pathways:
an
S
N
2-type
substitution
complex
a
halogen-atom
transfer
complex.
observed
pronounced
ligand
acceleration
addition,
which
correlates
with
couplings
azoles,
amines,
or
alkynes
alkyl
electrophiles.
Journal of the American Chemical Society,
Journal Year:
2024,
Volume and Issue:
146(22), P. 15176 - 15185
Published: May 21, 2024
Stepwise
oxidative
addition
of
copper(I)
complexes
to
form
copper(III)
species
via
single
electron
transfer
(SET)
events
has
been
widely
proposed
in
copper
catalysis.
However,
direct
observation
and
detailed
investigation
these
fundamental
steps
remain
elusive
owing
largely
the
typically
slow
rate
instability
species.
We
report
herein
a
novel
aryl-radical-enabled
stepwise
pathway
that
allows
for
formation
well-defined
alkyl–CuIII
from
CuI
complexes.
The
process
is
enabled
by
SET
an
aryl
diazonium
salt
CuII
radical.
Subsequent
iodine
abstraction
alkyl
iodide
radical
affords
radical,
which
then
reacts
with
complex.
structure
resultant
[(bpy)CuIII(CF3)2(alkyl)]
characterized
NMR
spectroscopy
X-ray
crystallography.
Competition
experiments
have
revealed
at
different
iodides
undergo
consistent
carbon-centered
radicals.
intermediate
formed
during
identified
as
four-coordinate
complex,
[CuII(CH3CN)2(CF3)2],
through
electronic
paramagnetic
resonance
(EPR)
studies.
catalytic
relevance
high-valent
organo-CuIII
demonstrated
C–C
bond-forming
reductive
elimination
reactivity.
Finally,
localized
orbital
bonding
analysis
formal
CuIII
indicates
inverted
ligand
fields
σ(Cu–CH2)
bonds.
These
results
demonstrate
catalysis
provide
general
strategy
investigate
Journal of the American Chemical Society,
Journal Year:
2023,
Volume and Issue:
145(48), P. 26152 - 26159
Published: Nov. 22, 2023
Despite
the
recent
advancements
of
Cu
catalysis
for
cross-coupling
alkyl
electrophiles
and
frequently
proposed
involvement
alkyl-Cu(III)
complexes
in
such
reactions,
little
is
known
about
reactivity
these
high-valent
complexes.
Specifically,
although
reversible
interconversion
between
an
alkyl-CuIII
complex
radical/CuII
pair
has
been
catalysis,
direct
observation
steps
well-defined
CuIII
remains
elusive.
In
this
study,
we
report
synthesis
investigation
complexes,
which
exclusively
undergo
a
Cu-C
homolysis
pathway
to
generate
radicals
CuII
species.
Kinetic
studies
suggest
bond
dissociation
energy
28.6
kcal/mol
CuIII-C
bonds.
Moreover,
four-coordinate
could
be
converted
solvated
alkyl-CuIII-(CF3)2,
undergoes
highly
efficient
C-CF3
bond-forming
reductive
elimination
even
at
low
temperatures
(-4
°C).
These
results
provide
strong
support
recombination
with
form
species,
elusive
step
that
Cu-catalyzed
mechanisms.
Furthermore,
our
work
demonstrated
significantly
influenced
by
subtle
changes
coordination
environment.
Lastly,
reactive
neutral
alkyl-CuIII-(CF3)2
species
(or
weakly
bound
solvent
molecules)
suggests
they
might
true
intermediates
many
trifluoromethylation
reactions.
Journal of the American Chemical Society,
Journal Year:
2024,
Volume and Issue:
146(33), P. 23555 - 23565
Published: Aug. 8, 2024
Copper-catalyzed
coupling
reactions
of
alkyl
halides
are
believed
to
prominently
involve
copper(II)
species
and
radicals
as
pivotal
intermediates,
with
their
exact
interaction
mechanism
being
the
subject
considerable
debate.
In
this
study,
a
visible
light-responsive
fluoroalkylcopper(III)
complex,
[(terpy)Cu(CF3)2(CH2CO2tBu)]
Trans-1,
was
designed
explore
mechanism.
Upon
exposure
blue
LED
irradiation,
Trans-1
undergoes
copper–carbon
bond
homolysis,
generating
Cu(II)
carbon-centered
radicals,
where
radical
then
recombines
intermediate,
resulting
in
formation
Cis-1,
Cis
isomer
Trans-1.
Beyond
this,
well-defined
fluoroalkylcopper(II)
intermediate
ligated
sterically
hindered
ligand
isolated
underwent
full
characterization
electronic
structure
studies.
The
collective
experimental,
computational,
spectroscopic
findings
work
strongly
suggest
that
organocopper(II)
engages
via
an
"oxidative
substitution"
mechanism,
which
is
likely
operational
pathway
for
copper-catalyzed
C–H
trifluoromethylation
reactions.
ACS Catalysis,
Journal Year:
2024,
Volume and Issue:
14(4), P. 2429 - 2454
Published: Feb. 1, 2024
Copper-catalyzed
radical
transformations
establish
a
powerful
toolkit
to
construct
versatile
complex
organic
compounds.
The
copper-mediated
bond
formation
step
of
radicals
plays
critical
role
in
controlling
chemo-
and
stereoselectivity
copper-catalyzed
transformation
reactions.
This
involves
three
possible
pathways:
ion-type
formation,
substitution,
reductive
elimination.
review
highlights
the
recent
advances
theoretical
studies
on
mechanisms
models
selectivity
Cu-mediated
radical-involved
providing
general
mechanistic
comprehension
this
key
elementary
copper
catalysis.