Nature Communications,
Год журнала:
2021,
Номер
12(1)
Опубликована: Фев. 11, 2021
Abstract
Hydrogen
atom
transfer
(HAT)
hydrogenation
has
recently
emerged
as
an
indispensable
method
for
the
chemoselective
reduction
of
unactivated
alkenes.
However,
hitherto
reported
systems
basically
require
stoichiometric
amounts
silanes
and
peroxides,
which
prevents
wider
applications,
especially
with
respect
to
sustainability
safety
concerns.
Herein,
we
report
a
silane-
peroxide-free
HAT
using
combined
cobalt/photoredox
catalysis
ascorbic
acid
(vitamin
C)
sole
reactant.
A
cobalt
salophen
complex
is
identified
optimal
cocatalyst
this
environmentally
benign
in
aqueous
media,
exhibits
high
functional-group
tolerance.
In
addition
its
applicability
late-stage
amino-acid
derivatives
drug
molecules,
offers
unique
advantage
direct
transformation
unprotected
sugar
allows
C
-glycoside
higher
yield
compared
previously
protocols.
The
proposed
mechanism
supported
by
experimental
theoretical
studies.
Journal of the American Chemical Society,
Год журнала:
2020,
Номер
142(31), С. 13481 - 13490
Опубликована: Июль 10, 2020
The
catalytic
enantioselective
synthesis
of
tetrahydrofurans,
which
are
found
in
the
structures
many
biologically
active
natural
products,
via
a
transition-metal-catalyzed
hydrogen
atom
transfer
(TM-HAT)
and
radical-polar
crossover
(RPC)
mechanism
is
described
herein.
Hydroalkoxylation
nonconjugated
alkenes
proceeded
efficiently
with
excellent
enantioselectivity
(up
to
94%
ee)
using
suitable
chiral
cobalt
catalyst,
N-fluoro-2,4,6-collidinium
tetrafluoroborate,
diethylsilane.
Surprisingly,
absolute
configuration
product
was
highly
dependent
on
steric
hindrance
silane.
Slow
addition
silane,
dioxygen
effect
solvent,
thermal
dependence,
DFT
calculation
results
supported
unprecedented
scenario
two
competing
selective
mechanisms.
For
less-hindered
diethylsilane,
high
concentration
diffused
carbon-centered
radicals
invoked
diastereoenrichment
an
alkylcobalt(III)
intermediate
by
radical
chain
reaction,
eventually
determined
product.
On
other
hand,
more
hindered
silane
resulted
less
opportunity
for
instead
facilitating
kinetic
resolution
during
late-stage
nucleophilic
displacement
alkylcobalt(IV)
intermediate.
Journal of the American Chemical Society,
Год журнала:
2020,
Номер
142(48), С. 20470 - 20480
Опубликована: Ноя. 18, 2020
Reported
herein
is
a
modular,
NiH-catalyzed
system
capable
of
proximal-selective
hydroamination
unactivated
alkenes
with
diverse
amine
sources.
The
key
to
the
successful
implementation
this
approach
promotion
NiH
insertion
into
even
highly
substituted
olefins
via
coordination
bidentate
directing
group
nickel
complex.
A
wide
range
primary
and
secondary
amines
can
be
installed
in
both
internal
terminal
excellent
regiocontrol
under
optimized
reaction
conditions.
This
protocol
flexible
general
for
preparation
variety
valuable
β-
γ-amino
acid
building
blocks
that
would
otherwise
difficult
synthesize.
utility
transformation
was
further
demonstrated
by
site-selective
late-stage
modification
complex
medicinally
relevant
molecules.
Combined
experimental
computational
studies
illuminate
detailed
mechanism.
Angewandte Chemie International Edition,
Год журнала:
2020,
Номер
59(26), С. 10316 - 10320
Опубликована: Март 10, 2020
Abstract
A
mild
visible‐light‐induced
Pd‐catalyzed
intramolecular
C−H
arylation
of
amides
is
reported.
The
method
operates
by
cleavage
a
C(sp
2
)−O
bond,
leading
to
hybrid
aryl
Pd‐radical
intermediates.
following
1,5‐hydrogen
atom
translocation,
cyclization,
and
rearomatization
steps
lead
valuable
oxindole
isoindoline‐1‐one
motifs.
Notably,
this
provides
access
products
with
readily
enolizable
functional
groups
that
are
incompatible
traditional
conditions.
Chemical Reviews,
Год журнала:
2021,
Номер
121(24), С. 14649 - 14681
Опубликована: Дек. 3, 2021
Asymmetric
hydroalkoxylation
of
alkenes
constitutes
a
redox-neutral
and
100%
atom-economical
strategy
toward
enantioenriched
oxygenated
building
blocks
from
readily
available
starting
materials.
Despite
their
great
potential,
catalytic
enantioselective
additions
alcohols
across
C–C
multiple
bond
are
particularly
underdeveloped,
especially
compared
to
other
hydrofunctionalization
methods
such
as
hydroamination.
However,
driven
by
some
recent
innovations,
e.g.,
asymmetric
MHAT
methods,
photocatalytic
the
development
extremely
strong
chiral
Brønsted
acids,
there
has
been
gratifying
surge
reports
in
this
burgeoning
field.
The
goal
review
is
survey
growing
landscape
highlighting
exciting
new
advances,
deconstructing
mechanistic
underpinnings,
drawing
insight
related
hydroacyloxylation
hydration.
A
deep
appreciation
underlying
principles
informs
an
understanding
various
selectivity
parameters
activation
modes
realm
alkene
while
simultaneously
evoking
outstanding
challenges
field
moving
forward.
Overall,
we
aim
lay
foundation
for
cross-fertilization
among
fields
spur
further
innovation
hydroalkoxylations
bonds.
Nature Communications,
Год журнала:
2021,
Номер
12(1)
Опубликована: Фев. 11, 2021
Abstract
Hydrogen
atom
transfer
(HAT)
hydrogenation
has
recently
emerged
as
an
indispensable
method
for
the
chemoselective
reduction
of
unactivated
alkenes.
However,
hitherto
reported
systems
basically
require
stoichiometric
amounts
silanes
and
peroxides,
which
prevents
wider
applications,
especially
with
respect
to
sustainability
safety
concerns.
Herein,
we
report
a
silane-
peroxide-free
HAT
using
combined
cobalt/photoredox
catalysis
ascorbic
acid
(vitamin
C)
sole
reactant.
A
cobalt
salophen
complex
is
identified
optimal
cocatalyst
this
environmentally
benign
in
aqueous
media,
exhibits
high
functional-group
tolerance.
In
addition
its
applicability
late-stage
amino-acid
derivatives
drug
molecules,
offers
unique
advantage
direct
transformation
unprotected
sugar
allows
C
-glycoside
higher
yield
compared
previously
protocols.
The
proposed
mechanism
supported
by
experimental
theoretical
studies.
