A
TEMPO-mediated
β-ketoalkylation
of
enaminoesters
with
cyclopropanols
under
metal-free
conditions
is
herein
described.
This
reaction
provides
a
straightforward
and
highly
efficient
route
to
β-keto
alkyl
substituted
for
the
first
time,
which
could
be
rapidly
efficiently
converted
into
synthetically
useful
2-alkoxycarbonyl
functionalized
1,5-diketones.
Moreover,
practicability
this
protocol
successfully
demonstrated
by
scale-up
experiments
late-stage
functionalization
natural
products
pharmaceutically
relevant
molecules.
Chemical Reviews,
Journal Year:
2020,
Volume and Issue:
121(1), P. 3 - 79
Published: Oct. 21, 2020
The
carbon–carbon
(C–C)
bond
cleavage
of
cyclopropanols
is
a
wide
area
research
with
much
current
activity.
This
review
highlights
new
developments
in
this
over
the
past
two
decades.
A
summary
made
three
main
reactivity
modes,
namely,
homoenolate
chemistry,
β-keto
radical
and
acid-catalyzed
ring-opening,
as
well
all
other
methods
for
C–C
functionalization
cyclopropanols,
including
base-mediated
metal-catalyzed
insertions
eliminations,
oxidative
fragmentation
using
hypervalent
iodine
reagents,
reactions
donor–acceptor
pericylic
reactions.
Emphasis
placed
on
synthetic
utility
related
derivatives,
which
have
emerged
unique
three-carbon
synthons.
Chemical Reviews,
Journal Year:
2023,
Volume and Issue:
123(16), P. 10302 - 10380
Published: Aug. 14, 2023
Nitroxides,
also
known
as
nitroxyl
radicals,
are
long-lived
or
stable
radicals
with
the
general
structure
R1R2N–O•.
The
spin
distribution
over
nitroxide
N
and
O
atoms
contributes
to
thermodynamic
stability
of
these
radicals.
presence
bulky
N-substituents
R1
R2
prevents
radical
dimerization,
ensuring
their
kinetic
stability.
Despite
reactivity
toward
various
transient
C
some
nitroxides
can
be
easily
stored
under
air
at
room
temperature.
Furthermore,
oxidized
oxoammonium
salts
(R1R2N═O+)
reduced
anions
(R1R2N–O–),
enabling
them
act
valuable
oxidants
reductants
depending
on
oxidation
state.
Therefore,
they
exhibit
interesting
across
all
three
states.
Due
fascinating
properties,
find
extensive
applications
in
diverse
fields
such
biochemistry,
medicinal
chemistry,
materials
science,
organic
synthesis.
This
review
focuses
versatile
For
use
other
important
fields,
we
will
refer
several
articles.
introductory
part
provides
a
brief
overview
history
chemistry.
Subsequently,
key
methods
for
preparing
discussed,
followed
by
an
examination
structural
diversity
physical
properties.
main
portion
this
is
dedicated
reactions,
wherein
parent
corresponding
serve
active
species.
It
demonstrated
that
functional
groups
(such
alcohols,
amines,
enolates,
alkanes
among
others)
efficiently
oxidized.
These
oxidations
carried
out
using
catalysts
combination
stoichiometric
terminal
oxidants.
By
reducing
anions,
become
effective
reagents
intriguing
Nitroxides
possess
ability
selectively
react
making
useful
terminating
cascade
reactions
forming
alkoxyamines.
Depending
structure,
alkoxyamines
weak
C–O
bonds,
allowing
thermal
generation
through
reversible
bond
cleavage.
Such
thermally
generated
participate
transformations,
discussed
end
review.
application
strategy
natural
product
synthesis
presented.
Organic Letters,
Journal Year:
2019,
Volume and Issue:
21(21), P. 8630 - 8634
Published: Oct. 16, 2019
A
three-component
cascade
bis-heteroannulation
reaction
is
described
that
provides
access
to
a
variety
of
benzo[4,5]thieno[3,2-c]isoquinoline
and
thieno[3,2-c]isoquinoline
compounds
from
easily
available
methylketoximes,
o-halobenzaldehydes,
elemental
sulfur.
Mechanistic
studies
reveal
two-step
process
involving
sequential
copper
sulfur
catalysis
relay.
ACS Catalysis,
Journal Year:
2023,
Volume and Issue:
13(3), P. 2118 - 2134
Published: Jan. 24, 2023
Dimerized
3-substituted
2-oxindoles
are
essential
building
blocks
for
the
total
synthesis
of
alkaloids.
Herein,
three
different
types
3-substituted-2-oxindoles
were
dimerized
with
a
41
examples
employing
TEMPO
as
redox
mediator
and
TEMPO+
an
in
situ
generated
electrocatalyst
using
control
potential
electrolysis
at
applied
only
0.8
V
versus
Ag/Ag+
nonaqueous
reference
electrode.
These
reactions
did
not
yield
any
product
formation
absence
TEMPO,
keeping
other
experimental
conditions
same.
Two-electron-
one-electron-transfer
pathways
operational
depending
on
oxidation
potentials
2-oxindoles.
3-Carboxylate-2-oxindoles
having
lower
oxidative
energy
barrier
two-electron-transfer
pathway
followed
hydride-transfer
mechanism
to
generate
carbocation,
which
thereafter
reacted
enol
form
oxindole
produce
On
hand,
3-alkyl-2-oxindoles
3-alkylcarboxylate-2-oxindoles
had
significantly
higher
compared
3-carboxylate-2-oxindoles
radical
species
dimerization.
The
two-electron
transfer
was
faster
one-electron
pathway,
evident
from
reaction
time
(15
min
vs
1
h
20
or
longer),
due
second-order
rate
constant
(1.2
M–1
s–1)
(0.29
s–1).
Furthermore,
four
aspects
transforming
greener
electro-organic
have
been
demonstrated.
They
follows:
(a)
electron-transfer
measurement
alternative
method
optimization
instead
lengthy
isolation,
(b)
prevention
electrode
passivation
electrocatalysis
routes,
(c)
recovery
electrolyte,
(d)
mild
electrolysis.
Finally,
efficient
electrochemical
strategy
has
demonstrated
dimeric
hexahydropyrrolo[2,3-b]indole
alkaloids,
(±)-chimonanthine
(I)
(±)-folicanthine
(II).
Organic Letters,
Journal Year:
2023,
Volume and Issue:
25(5), P. 838 - 842
Published: Jan. 27, 2023
A
copper-catalyzed
annulation
of
O-acyl
oximes
with
cyclic
1,3-diones
has
been
developed
for
the
concise
synthesis
7,8-dihydroindolizin-5(6H)-ones
and
cyclohexanone-fused
furans
through
substituent-controlled
selective
radical
coupling
process.
2-Alkyl
undergo
C-C
coupling,
while
2-unsubstituted
C-O
coupling.
European Journal of Organic Chemistry,
Journal Year:
2024,
Volume and Issue:
27(9)
Published: Feb. 8, 2024
Abstract
Cycloalkanols
ring‐opening
transformation
is
one
of
the
most
valuable
and
wide
area
research.
Among
numerous
methods
that
have
been
developed,
transition‐metal‐free
approaches
attracted
great
interest
from
both
chemists
pharmacologists.
This
largely
due
to
advantages
being
environmentally
benign,
cost‐effective
operationally
simple.
Here
we
provide
a
comprehensive
outline
on
recent
advances
in
synthesis
distally
substituted
ketones
cyclic
compounds
via
cycloalkanols
under
conditions.
Angewandte Chemie International Edition,
Journal Year:
2019,
Volume and Issue:
59(10), P. 3900 - 3904
Published: Dec. 23, 2019
A
deconstructive
oxygenation
of
unstrained
primary
cycloalkanamines
has
been
developed
for
the
first
time
using
an
auto-oxidative
aromatization
promoted
C(sp3
)-C(sp3
)
bond
cleavage
strategy.
This
metal-free
method
involves
substitution
reaction
with
hydrazonyl
chlorides
and
subsequent
annulation
to
in
situ
generate
pre-aromatics,
followed
by
N-radical-promoted
ring-opening
further
2,2,6,6-tetramethylpiperidine-1-oxyl
(TEMPO)
m-cholorperoxybenzoic
acid
(mCPBA).
Consequently,
a
series
1,2,4-triazole-containing
acyclic
carbonyl
compounds
were
efficiently
produced.
protocol
features
one-pot
operation,
mild
conditions,
high
regioselectivity
efficiency,
broad
substrate
scope,
is
compatible
alkaloids,
osamines,
peptides,
as
well
steroids.
Angewandte Chemie International Edition,
Journal Year:
2021,
Volume and Issue:
61(1)
Published: Nov. 4, 2021
Abstract
The
site‐selective
C−H
functionalization
of
heteroarenes
is
considerable
importance
for
streamlining
the
rapid
modification
bioactive
molecules.
Herein,
we
report
a
general
strategy
visible‐light‐induced
β‐carbonyl
alkylation
at
C4
position
pyridines
with
high
site
selectivity
using
various
cyclopropanols
and
N‐amidopyridinium
salts.
In
this
process,
hydrogen‐atom
transfer
between
generated
sulfonamidyl
radicals
O−H
bonds
generates
radicals,
providing
efficient
access
to
synthetically
valuable
β‐pyridylated
(aryl)ketones,
aldehydes,
esters
broad
functional‐group
tolerance.
addition,
mild
method
serves
as
an
effective
tool
late‐stage
complex
medicinally
relevant
