Nature Communications,
Journal Year:
2021,
Volume and Issue:
12(1)
Published: Feb. 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.
Accounts of Chemical Research,
Journal Year:
2020,
Volume and Issue:
53(3), P. 547 - 560
Published: Feb. 20, 2020
Electrochemistry
has
been
used
as
a
tool
to
drive
chemical
reactions
for
over
two
centuries.
With
the
help
of
an
electrode
and
power
source,
chemists
are
bestowed
with
imaginary
reagent
whose
potential
can
be
precisely
dialed
in.
The
theoretically
infinite
redox
range
renders
electrochemistry
capable
oxidizing
or
reducing
some
most
tenacious
compounds
(e.g.,
F
Chemical Reviews,
Journal Year:
2020,
Volume and Issue:
120(24), P. 13382 - 13433
Published: Nov. 29, 2020
Synergistic
catalysis,
a
type
of
plural
catalysis
which
utilizes
at
least
two
different
catalysts
to
enable
reaction
between
separately
activated
substrates,
has
unlocked
plethora
previously
unattainable
transformations
and
novel
chemical
reactivity.
Despite
the
appreciable
utility
synergistic
specific
examples
involving
transition
metals
have
been
limited,
as
ensuring
judicious
choice
parameters
prevent
deactivation
catalysts,
undesirable
monocatalytic
event(s)
leading
side
products,
or
premature
termination
other
potentially
troublesome
outcomes
present
formidable
challenge.
Excluding
those
driven
by
photocatalytic
mechanisms,
this
review
will
highlight
reported
reactions
that
make
use
simultaneous
catalytic
cycles
metal
catalysts.
Journal of the American Chemical Society,
Journal Year:
2019,
Volume and Issue:
141(16), P. 6726 - 6739
Published: April 3, 2019
Historically
accessed
through
two-electron,
anionic
chemistry,
ketones,
alcohols,
and
amines
are
of
foundational
importance
to
the
practice
organic
synthesis.
After
placing
this
work
in
proper
historical
context,
Article
reports
development,
full
scope,
a
mechanistic
picture
for
strikingly
different
way
forging
such
functional
groups.
Thus,
carboxylic
acids,
once
converted
redox-active
esters
(RAEs),
can
be
utilized
as
formally
nucleophilic
coupling
partners
with
other
derivatives
(to
produce
ketones),
imines
benzylic
amines),
or
aldehydes
alcohols).
The
reactions
uniformly
mild,
operationally
simple,
and,
case
ketone
synthesis,
broad
scope
(including
several
applications
simplification
synthetic
problems
parallel
synthesis).
Finally,
an
extensive
study
synthesis
is
performed
trace
elementary
steps
catalytic
cycle
provide
end-user
clear
understandable
rationale
selectivity,
role
additives,
underlying
driving
forces
involved.
Journal of the American Chemical Society,
Journal Year:
2020,
Volume and Issue:
142(4), P. 1698 - 1703
Published: Jan. 6, 2020
The
highly
regioselective
electrophotocatalytic
C–H
functionalization
of
ethers
is
described.
These
reactions
are
catalyzed
by
a
trisaminocyclopropenium
(TAC)
ion
at
mild
electrochemical
potential
with
visible
light
irradiation.
Ethers
undergo
oxidant-free
coupling
isoquinolines,
alkenes,
alkynes,
pyrazoles,
and
purines
typically
high
regioselectivity
for
the
less-hindered
α-position.
reaction
proposed
to
operate
via
hydrogen
atom
transfer
(HAT)
from
substrate
photoexcited
TAC
radical
dication,
thus
demonstrating
new
reactivity
mode
this
electrophotocatalyst.
Journal of the American Chemical Society,
Journal Year:
2019,
Volume and Issue:
141(19), P. 7709 - 7714
Published: April 29, 2019
Metal-hydride
hydrogen
atom
transfer
(MHAT)
functionalizes
alkenes
with
predictable
branched
(Markovnikov)
selectivity.
The
breadth
of
these
transformations
has
been
confined
to
π-radical
traps;
no
sp3
electrophiles
have
reported.
Here
we
describe
a
Mn/Ni
dual
catalytic
system
that
hydroalkylates
unactivated
olefins
alkyl
halides,
yielding
aliphatic
quaternary
carbons.
Journal of the American Chemical Society,
Journal Year:
2021,
Volume and Issue:
143(40), P. 16470 - 16485
Published: Sept. 30, 2021
The
value
of
catalytic
dehydrogenation
aliphatics
(CDA)
in
organic
synthesis
has
remained
largely
underexplored.
Known
homogeneous
CDA
systems
often
require
the
use
sacrificial
hydrogen
acceptors
(or
oxidants),
precious
metal
catalysts,
and
harsh
reaction
conditions,
thus
limiting
most
existing
methods
to
non-
or
low-functionalized
alkanes.
Here
we
describe
a
visible-light-driven,
dual-catalyst
system
consisting
inexpensive
organophotoredox
base-metal
catalysts
for
room-temperature,
acceptorless-CDA
(Al-CDA).
Initiated
by
photoexited
2-chloroanthraquinone,
process
involves
H
atom
transfer
(HAT)
form
alkyl
radicals,
which
then
react
with
cobaloxime
produce
olefins
H2.
This
operationally
simple
method
enables
direct
readily
available
chemical
feedstocks
diversely
functionalized
olefins.
For
example,
demonstrate,
first
time,
oxidant-free
desaturation
thioethers
amides
alkenyl
sulfides
enamides,
respectively.
Moreover,
system's
exceptional
site
selectivity
functional
group
tolerance
are
illustrated
late-stage
14
biologically
relevant
molecules
pharmaceutical
ingredients.
Mechanistic
studies
have
revealed
dual
HAT
provided
insights
into
origin
reactivity
selectivity.
