Science,
Journal Year:
2021,
Volume and Issue:
371(6536), P. 1338 - 1345
Published: March 25, 2021
Heteroaromatics
lured
into
cycloadditions
The
Diels-Alder
reaction
is
widely
used
to
produce
six-membered
carbon
rings
from
alkenes
and
dienes.
such
as
quinolines
resemble
dienes
in
principle,
but
practice
their
pairs
of
double
bonds
are
inert
toward
because
aromatic
stabilization.
Ma
et
al.
report
that
by
using
an
iridium
photosensitizer,
they
could
excite
related
azaarenes
triplet
states,
thereby
disrupting
the
aromaticity
enabling
intermolecular,
Diels-Alder–like
reactivity
(see
Perspective
Schmidt).
reactions
proceeded
exclusively
at
flanking
carbons
outside
nitrogen-containing
ring.
Science
,
this
issue
p.
1338
;
see
also
1313
Accounts of Chemical Research,
Journal Year:
2022,
Volume and Issue:
55(17), P. 2510 - 2525
Published: Aug. 9, 2022
Exploring
the
enormous
chemical
space
through
an
expedient
building-up
of
molecular
diversity
is
important
goal
organic
chemistry.
The
development
synthetic
methods
toward
molecules
with
unprecedented
structural
motifs
lays
foundation
for
wide
applications
ranging
from
pharmaceutical
chemistry
to
materials
science.
In
this
regard,
dearomatization
arenes
has
been
recognized
as
a
unique
strategy
since
it
provides
novel
retrosynthetic
disconnections
various
spiro
or
fused
polycyclic
increased
saturation
and
stereoisomerism.
However,
inherent
thermodynamic
challenges
are
associated
processes.
disruption
aromaticity
arene
substrates
usually
requires
large
energy
inputs,
which
makes
harsh
conditions
necessary
many
ground-state
reactions.
Therefore,
further
expansion
scope
reactions
remains
major
problem
not
fully
solved
in
chemistry.The
past
decade
witnessed
tremendous
progress
on
photocatalytic
under
visible
light.
Particularly,
via
transfer
mechanism
have
unlocked
new
opportunities
Mediated
by
appropriately
chosen
photosensitizers,
aromatic
can
be
excited.
This
kind
precise
input
might
make
feasible
some
that
otherwise
unfavorable
thermal
because
significant
increases
substrates.
Nevertheless,
lifetimes
key
intermediates
energy-transfer-enabled
reactions,
such
excited-state
aromatics
downstream
biradical
species,
quite
short.
How
regulate
reactivities
these
transient
achieve
exclusive
selectivity
certain
reaction
pathway
among
possibilities
crucial
issue
addressed.Since
2019,
our
group
reported
series
visible-light-induced
dearomative
cycloaddition
indole
pyrrole
derivatives.
It
was
found
units
excited
irradiation
light
presence
suitable
photosensitizer.
These
readily
undergo
[m
+
n]
tethered
unsaturated
functionalities
including
alkenes,
alkynes,
N-alkoxy
oximes,
(hetero)arenes,
vinylcyclopropanes.
yield
indolines
pyrrolines
highly
strained
small-
and/or
medium-sized
rings
embedded,
possess
bridge-
cagelike
topologies.
Systematic
mechanistic
studies
confirmed
involvement
process.
Density
functional
theory
(DFT)
calculations
revealed
correlation
between
substrate
structure
excitation
efficiency,
accelerated
optimization
parameters.
Meanwhile,
DFT
demonstrated
competition
kinetically
thermodynamically
controlled
pathways
open-shell
singlet
intermediates,
allowed
complete
switches
[2
2]
1,5-hydrogen
atom
oximes
[4
naphthalene.
Furthermore,
ab
initio
dynamics
(AIMD)
simulations
uncovered
post-spin
crossing
dynamic
effects,
determine
regioselectivity
recombination
step
pyrrole-derived
vinylcyclopropanes.An
increasing
number
scientists
joined
research
contributed
more
elegant
examples
area.
mechanism,
although
still
its
infancy,
exhibited
great
potential
synthesis
hardly
accessed
other
methods.
We
believe
future
will
push
boundary
find
related
disciplines.
ACS Catalysis,
Journal Year:
2022,
Volume and Issue:
12(3), P. 1857 - 1878
Published: Jan. 20, 2022
A
highly
selective
and
divergent
synthesis
enables
access
to
various
molecules
has
garnered
broad
interest
from
not
only
organic
chemists
but
also
medicinal
biologists
who
work
with
chemical
libraries.
Since
the
20th
century,
such
transformations
have
been
achieved
using
transition-metal-catalyzed
reactions,
in
which
choice
of
catalyst
or
ligand
crucially
affects
selectivity.
Over
past
several
decades,
photocatalysts
attracted
a
considerable
amount
attention
because
they
provide
additional
ways
control
reaction
intermediates
product
selectivity
via
electron
energy
transfer.
From
this
perspective,
we
highlight
recent
development
switchable
syntheses
photocatalysts,
are
difficult
achieve
classical
catalytic
transformations.
Journal of the American Chemical Society,
Journal Year:
2021,
Volume and Issue:
143(33), P. 13441 - 13449
Published: Aug. 16, 2021
Visible-light-induced
cycloaddition
reactions
initiated
via
energy-transfer
processes
have
recently
evolved
as
powerful
methods
for
the
construction
of
strained
cyclic
molecules
that
are
not
easily
accessed
using
known
ground-state
synthetic
methods.
Particularly,
by
excitation
aromatic
rings
provide
an
alternative
solution
to
direct
transformations
feedstocks
under
scheme
dearomatization.
Vinylcyclopropanes
(VCPs)
well-known
reagents
in
radical
clock
experiments,
working
a
probe
detect
transient
intermediates.
However,
applications
this
regard
still
remain
limited
due
uncontrollable
selectivities.
Herein,
we
report
visible-light-induced
dearomatization
indole-
or
pyrrole-tethered
VCPs,
which
several
competitive
reaction
pathways,
including
[5
+
2],
[2
interrupted
and
4]
cycloadditions,
can
be
well
regulated
engineering
substrate
structures
tuning
conditions.
The
mechanism
has
been
explored
combined
experimental
computational
investigations.
These
convenient
method
synthesize
structurally
diverse
polycyclic
with
high
efficiency
good
selectivity.
Angewandte Chemie International Edition,
Journal Year:
2021,
Volume and Issue:
60(13), P. 7036 - 7040
Published: Jan. 15, 2021
Abstract
Herein
we
report
visible‐light‐induced
intramolecular
double
dearomative
cycloaddition
of
arenes.
Compared
with
the
well‐known
photodimerization
arenes
under
ultraviolet
irradiation,
current
reactions
are
carried
out
mild
conditions
and
feature
wide
substrate
scope.
A
large
array
structurally‐diverse
polycyclic
indoline
derivatives
is
afforded
in
high
yields
(up
to
98
%)
exclusive
diastereoselectivity
(>20:1
dr)
via
[4+2]
or
[2+2]
pathway.
Journal of the American Chemical Society,
Journal Year:
2022,
Volume and Issue:
144(38), P. 17680 - 17691
Published: Sept. 15, 2022
Photochemical
dearomative
cycloaddition
has
emerged
as
a
useful
strategy
to
rapidly
generate
molecular
complexity.
Within
this
context,
stereo-
and
regiocontrolled
intermolecular
para-cycloadditions
are
rare.
Herein,
method
achieve
photochemical
of
quinolines
alkenes
is
shown.
Emphasis
placed
on
generating
sterically
congested
products
reaction
highly
substituted
allenes.
In
addition,
the
mechanistic
details
process
studied,
which
revealed
reversible
radical
addition
selectivity-determining
recombination.
The
regio-
stereochemical
outcome
also
rationalized.
