Organic Letters,
Journal Year:
2022,
Volume and Issue:
24(25), P. 4592 - 4597
Published: June 21, 2022
A
cobalt-catalyzed
multipositional
isomerization
of
conjugated
dienes
has
been
reported
for
the
first
time
using
an
8-oxazoline
iminoquinoline
ligand.
This
reaction
is
operationally
simple
and
atom-economical
readily
available
starting
materials
with
E/Z
mixture
to
access
disubstituted
1,3-dienes
excellent
yields
good
E,E
stereoselectivity.
The
mechanism
via
alkene
insertion
cobalt
hydride
species
β-H
elimination
a
π-allyl
intermediate
proposed
on
basis
deuterium
labeling
control
experiments
density
functional
theory
calculations.
Journal of the American Chemical Society,
Journal Year:
2021,
Volume and Issue:
144(1), P. 137 - 144
Published: Dec. 30, 2021
A
light-driven
method
for
the
contra-thermodynamic
positional
isomerization
of
olefins
is
described.
In
this
work,
stepwise
PCET
activation
a
more
substituted
and
thermodynamically
stable
olefin
substrate
mediated
by
an
excited-state
oxidant
Brønsted
base
to
afford
allylic
radical
that
captured
Cr(II)
cocatalyst
furnish
allylchromium(III)
intermediate.
situ
protodemetalation
allylchromium
complex
methanol
highly
regioselective
affords
isomerized
less
alkene
product.
The
higher
oxidation
potential
isomer
renders
it
inert
further
oxidant,
enabling
accumulate
in
solution
over
course
reaction.
broad
range
isopropylidene
substrates
are
accommodated,
including
enol
ethers,
enamides,
styrenes,
1,3-dienes,
tetrasubstituted
alkyl
olefins.
Mechanistic
investigations
step
also
presented.
Angewandte Chemie International Edition,
Journal Year:
2024,
Volume and Issue:
63(21)
Published: March 18, 2024
Abstract
Because
internal
alkenes
are
more
challenging
synthetic
targets
than
terminal
alkenes,
metal‐catalyzed
olefin
mono‐transposition
(i.e.,
positional
isomerization)
approaches
have
emerged
to
afford
valuable
E
‐
or
Z‐
from
their
complementary
alkene
feedstocks.
However,
the
applicability
of
these
methods
has
been
hampered
by
lack
generality,
commercial
availability
precatalysts,
and
scalability.
Here,
we
report
a
nickel‐catalyzed
platform
for
stereodivergent
/
Z
‐selective
synthesis
at
room
temperature.
Commercial
reagents
enable
this
one‐carbon
transposition
‐internal
via
Ni−H‐mediated
insertion/elimination
mechanism.
Though
mechanistic
regime
is
same
in
both
systems,
underlying
pathways
that
lead
each
active
catalysts
distinct,
with
catalyst
forming
comproportionation
an
oxidative
addition
complex
followed
substrate
protonation
metal
trialkylphosphonium
salt
additive.
In
case,
ligand
sterics
denticity
control
stereochemistry
prevent
over‐isomerization.
Journal of the American Chemical Society,
Journal Year:
2021,
Volume and Issue:
143(25), P. 9648 - 9656
Published: June 21, 2021
Vinylcarbene
insertion
into
the
nitrogen–hydrogen
(N–H)
bond
of
amines
allows
direct
access
to
α,β-unsaturated
γ-amino
acid
derivatives,
meeting
a
marked
challenge
in
control
regio-
and
enantioselectivities.
Here,
we
report
highly
γ-selective
enantioselective
N–H
bonds
aliphatic
or
aromatic
secondary
with
vinyl
substituted
α-diazo
pyrazoleamides
using
high-spin
chiral
N,N′-dioxide/cobalt(II)
complex
catalyst.
The
method
affords
wide
variety
valuable
optically
active
Z-
E-type
amides.
Calculation
reveals
spin
state
change
from
quartet
cobalt(II)
doublet
Co(II)-carbene
species
for
facile
Z-selective
nucleophilic
addition.
Journal of the American Chemical Society,
Journal Year:
2021,
Volume and Issue:
143(49), P. 20633 - 20639
Published: Dec. 6, 2021
Chiral
cyclic
olefins,
1-methylcyclohexenes,
are
versatile
building
blocks
for
the
synthesis
of
pharmaceuticals
and
natural
products.
Despite
prevalence
these
structural
motifs,
development
efficient
synthetic
methods
remains
an
unmet
challenge.
Herein
we
report
a
novel
desymmetric
isomerization
exocyclic
olefins
using
series
newly
designed
chiral
cobalt
catalysts,
which
enables
straightforward
construction
1-methylcyclohexenes
with
diversified
functionalities.
The
utility
this
methodology
is
highlighted
by
concise
enantioselective
product,
β-bisabolene.
versatility
reaction
products
further
demonstrated
multifarious
derivatizations.
National Science Review,
Journal Year:
2023,
Volume and Issue:
11(2)
Published: Dec. 19, 2023
ABSTRACT
Iron
catalysts
are
ideal
transition
metal
because
of
the
Earths
abundant,
cheap,
biocompatible
features
iron
salts.
often
have
unique
open-shell
structures
that
easily
undergo
spin
crossover
in
chemical
transformations,
a
feature
rarely
found
noble
catalysts.
Unfortunately,
little
is
known
currently
about
how
structure
and
affect
reactivity
selectivity
catalysts,
which
makes
development
low
efficient
trial-and-error
program.
In
this
paper,
combination
experiments
theoretical
calculations
revealed
iron-catalyzed
hydrosilylation
alkynes
typical
spin-crossover
catalysis.
Deep
insight
into
electronic
set
well-defined
active
formal
Fe(0)
spin-delocalization
between
center
1,10-phenanthroline
ligand
effectively
regulates
center's
oxidation
state
to
meet
opposite
electrostatic
requirements
oxidative
addition
reductive
elimination,
respectively,
essential
for
electron
transfer
process.
The
triplet
was
achieving
high
regioselectivity
through
tuning
nonbonding
interactions.
These
findings
provide
an
important
reference
understanding
effect
catalyst
on
reaction.
It
inspiring
other
Earth-abundant
especially
from
point
view
development.
Journal of the American Chemical Society,
Journal Year:
2024,
Volume and Issue:
146(39), P. 26766 - 26776
Published: Sept. 20, 2024
The
isomerization
of
1,1-disubstituted
alkenes
through
1,3-hydrogen
shift
is
an
atom-efficient
route
for
synthesizing
trisubstituted
alkenes,
which
are
important
moieties
in
many
natural
products,
pharmaceuticals,
and
organic
materials.
However,
this
reaction
often
encounters
regio-
stereoselectivity
challenges,
typically
yielding
ACS Catalysis,
Journal Year:
2021,
Volume and Issue:
11(11), P. 6741 - 6749
Published: May 26, 2021
A
stereoselective
alkene
isomerization
and
sequential
hydroarylation
with
arylboronic
acid
using
a
nickel(0)
catalyst
has
been
developed.
The
bulky
monophosphine
PAd2(n-Bu)
is
an
effective
ligand
in
these
reactions
to
furnish
both
various
stereo-defined
internal
alkenes
products
(isomerization:
up
98%,
E/Z
=
98:2;
tandem
hydroarylation:
82%).
Mechanistic
studies
based
on
experiments
computational
calculations
suggested
that
the
proceeds
via
intra-
or
intermolecular
hydrogen
shift.
Furthermore,
concerted
multibond
recombination
boronic
acid-assisted
oxidative
protometallation
of
was
found
be
reasonable
mechanism
for
formation
alkylnickel(II)
species
from
alkene,
nickel(0),
alcohol,
hydroarylation.
ACS Catalysis,
Journal Year:
2021,
Volume and Issue:
11(16), P. 10138 - 10147
Published: July 30, 2021
An
iron
dichloride
complex
[Fe]Cl2
supported
by
a
pincer
phosphine–pyridine–imidazoline
(PNNimid)
ligand
{[Fe]Cl2
=
(PNNimid)FeCl2},
upon
activation
with
NaHBEt3,
catalyzes
the
isomerization
of
1,1-disubstituted
alkenyl
boronates
to
synthetically
valuable
but
previously
difficult-to-access
trisubstituted
(Z)-alkenyl
excellent
regio-
and
stereoselectivity.
The
loading
catalyst
activator
relative
was
found
affect
selectivity
catalytic
efficiency.
In
situ
solvent-assisted
electrospray
ionization
mass
(SAESI-MS)
studies
revealed
generation
two
catalytically
competent
species
depending
on
Fe/NaHBEt3
ratios:
reaction
1.5
equiv
NaHBEt3
predominantly
formed
monohydride
chloride
[Fe]HCl,
while
treatment
3
furnished
dihydride
[Fe]H2.
addition,
alkyl
intermediates
resulting
from
insertion
boronate
into
Fe–H
bonds
[Fe]HCl
[Fe]H2
were
successfully
captured
SAESI-MS.
hydride
catalysts
are
sensitive
steric
properties
alkene
substrates:
is
efficient
for
synthesis
less
hindered
alkyl-bearing
boronates,
whereas
favorable
sterically
more
demanding
aryl-substituted
products.
synthetic
utility
these
products
demonstrated
stereoselective
multisubstituted
conjugated
dienes
cyercene
A.
Journal of the American Chemical Society,
Journal Year:
2023,
Volume and Issue:
145(22), P. 11978 - 11987
Published: May 25, 2023
Transition
metal
catalyzed
alkene
double
bond
transposition
usually
involves
hydride
intermediates.
Despite
significant
advances
in
the
design
of
catalysts
that
dictate
product
selectivity,
control
over
substrate
selectivity
is
less
advanced
and
transition
selectively
transpose
bonds
substrates
containing
multiple
1-alkene
functionalities
are
rare.
Herein,
we
report
three-coordinate
high
spin
(S
=
2)
Fe(II)
imido
complex
[Ph2B(tBuIm)2Fe═NDipp][K(18-C-6)THF2]
(1-K(18-C-6))
catalyzes
1,3-proton
transfer
from
to
afford
2-alkene
products.
Mechanistic
investigations
involving
kinetics,
competition,
isotope
labeling
studies,
supported
by
experimentally
calibrated
DFT
computations,
strongly
support
an
unusual
nonhydridic
mechanism
for
enabled
cooperative
action
iron
center
basic
ligand.
As
dictated
pKa
allylic
protons,
this
catalyst
enables
regioselective
C═C
1-alkenes.
The
state
allows
a
wide
scope
functional
groups
be
tolerated,
including
those
typical
poisons,
such
as
amines,
N-heterocycles,
phosphines.
These
results
demonstrate
new
strategy
metal-catalyzed
with
predictable
regioselectivity.