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:
2020,
Volume and Issue:
142(19), P. 8910 - 8917
Published: April 21, 2020
Stereoselective
synthesis
of
trisubstituted
alkenes
is
a
long-standing
challenge
in
organic
chemistry,
due
to
the
small
energy
differences
between
E
and
Z
isomers
(compared
with
1,2-disubstituted
alkenes).
Transition
metal-catalyzed
isomerization
1,1-disubstituted
can
serve
as
an
alternative
approach
alkenes,
but
it
remains
underdeveloped
owing
issues
relating
reaction
efficiency
stereoselectivity.
Here
we
show
that
novel
cobalt
catalyst
overcome
these
challenges
provide
efficient
stereoselective
access
broad
range
alkenes.
This
protocol
compatible
both
mono-
dienes
exhibits
good
functional
group
tolerance
scalability.
Moreover,
has
proven
be
useful
tool
construct
luminophores
deuterated
alkene.
A
preliminary
study
mechanism
suggests
cobalt-hydride
pathway
involved
reaction.
The
high
stereoselectivity
attributed
π–π
stacking
effect
steric
hindrance
substrate
catalyst.
Journal of the American Chemical Society,
Journal Year:
2020,
Volume and Issue:
142(42), P. 18223 - 18230
Published: Sept. 29, 2020
The
catalytic
isomerization
of
C–C
double
bonds
is
an
indispensable
chemical
transformation
used
to
deliver
higher-value
analogues
and
has
important
utility
in
the
industry.
Notwithstanding
advances
reported
this
field,
there
compelling
demand
for
a
general
solution
that
enables
precise
control
C═C
bond
migration
position,
both
cyclic
acyclic
systems,
furnish
disubstituted
trisubstituted
alkenes.
Here,
we
show
amounts
appropriate
earth-abundant
iron-based
complex,
base
boryl
compound,
promote
efficient
controllable
alkene
transposition.
Mechanistic
investigations
reveal
these
processes
likely
involve
situ
formation
iron-hydride
species
which
promotes
olefin
through
sequential
insertion/β-hydride
elimination.
Through
strategy,
regiodivergent
access
different
products
from
one
substrate
can
be
facilitated,
isomeric
mixtures
commonly
found
petroleum-derived
feedstock
transformed
single
product,
unsaturated
moieties
embedded
within
linear
heterocyclic
biologically
active
entities
obtained.
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(8), P. 3070 - 3074
Published: Feb. 17, 2021
Double-bond
transposition
in
alkenes
(isomerization)
offers
opportunities
for
the
synthesis
of
bioactive
molecules,
but
requires
high
selectivity
to
avoid
mixtures
products.
Generation
Z-alkenes,
which
are
present
many
natural
products
and
pharmaceuticals,
is
particularly
challenging
because
it
usually
less
thermodynamically
favorable
than
generation
E
isomers.
We
report
a
β-dialdiminate-supported,
high-spin
cobalt(I)
complex
that
can
convert
terminal
alkenes,
including
previously
recalcitrant
allylbenzenes,
Z-2-alkenes
with
unprecedentedly
regioselectivity
stereoselectivity.
Deuterium
labeling
studies
indicate
catalyst
operates
through
π-allyl
mechanism,
different
from
alkyl
mechanism
followed
by
other
Z-selective
catalysts.
Computations
triplet
alkene
undergoes
spin
state
change
resting-state
singlet
lowest-energy
C–H
activation
transition
state,
leads
Z
product.
This
suggests
this
enables
differentiate
stereodefining
barriers
system,
more
generally
spin-state
changes
may
offer
route
toward
novel
stereocontrol
methods
first-row
metals.
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.
Angewandte Chemie International Edition,
Journal Year:
2022,
Volume and Issue:
61(14)
Published: Jan. 28, 2022
The
structural
diversity
of
sp3
-triorganometallic
reagents
enhances
their
potentiality
in
the
modular
construction
molecular
complexity
chemical
synthesis.
Despite
significant
achievements
on
preparation
1,1,1-
and
1,1,2-triorganometallic
B,B,B-reagents,
catalytic
approaches
that
enable
installation
multiple
boryl
groups
at
skipped
carbons
unactivated
alkenes
still
remain
elusive.
Herein,
we
report
a
cobalt-catalyzed
selective
triborylation
reaction
to
access
synthetically
versatile
1,1,3-triborylalkanes.
This
protocol
provides
general
platform
for
regioselective
trifunctionalization
alkenes,
its
utility
is
highlighted
by
synthesis
various
value-added
chemicals
from
readily
accessible
alkenes.
Mechanistic
studies,
including
deuterium-labelling
experiments
evaluation
potential
reactive
intermediates,
provide
insight
into
experimentally
observed
chemo-
regioselectivity.
Journal of the American Chemical Society,
Journal Year:
2022,
Volume and Issue:
144(38), P. 17359 - 17364
Published: Sept. 15, 2022
Investigation
on
asymmetric
hydrogenation
of
olefins
is
great
importance
in
both
pharmaceutical
molecule
synthesis
and
chemical
industry
due
to
the
high
demand
for
enantiopure
compounds.
The
established
methods
often
require
geometrically
pure
olefins.
enantioconvergent
reaction
provided
possibility
access
a
single
stereoisomer
via
E/Z-olefin
mixtures;
however,
polar
functional
group
next
carbon-carbon
double
bond
was
usually
necessary.
Here,
we
reported
cobalt-catalyzed
readily
available
minimally
functionalized
mixtures.
This
strategy
shows
good
tolerance
provides
an
alternative
means
transformation.
preliminary
mechanistic
studies
indicated
that
isomerization
key
achieve
convergent
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(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.