Journal of the American Chemical Society,
Год журнала:
2021,
Номер
144(1), С. 145 - 152
Опубликована: Дек. 30, 2021
The
positional
isomerization
of
C═C
double
bonds
is
a
powerful
strategy
for
the
interconversion
alkene
regioisomers.
However,
existing
methods
provide
access
to
thermodynamically
more
stable
isomers
from
less
starting
materials.
Here,
we
report
discovery
dual
catalyst
system
that
promotes
contra-thermodynamic
under
photochemical
irradiation,
providing
terminal
directly
conjugated,
internal
utility
method
demonstrated
in
deconjugation
diverse
electron-rich/electron-poor
alkenes
and
through
strategic
application
natural
product
synthesis.
Mechanistic
studies
are
consistent
with
regiospecific
bimolecular
homolytic
substitution
(SH2′)
mechanism
proceeding
an
allyl-cobaloxime
intermediate.
Journal of the American Chemical Society,
Год журнала:
2021,
Номер
144(1), С. 137 - 144
Опубликована: Дек. 30, 2021
A
light-driven
method
for
the
contra-thermodynamic
positional
isomerization
of
olefins
is
described.
In
this
work,
stepwise
PCET
activation
a
more
substituted
and
thermodynamically
stable
olefin
substrate
mediated
by
an
excited-state
oxidant
Brønsted
base
to
afford
allylic
radical
that
captured
Cr(II)
cocatalyst
furnish
allylchromium(III)
intermediate.
situ
protodemetalation
allylchromium
complex
methanol
highly
regioselective
affords
isomerized
less
alkene
product.
The
higher
oxidation
potential
isomer
renders
it
inert
further
oxidant,
enabling
accumulate
in
solution
over
course
reaction.
broad
range
isopropylidene
substrates
are
accommodated,
including
enol
ethers,
enamides,
styrenes,
1,3-dienes,
tetrasubstituted
alkyl
olefins.
Mechanistic
investigations
step
also
presented.
Journal of the American Chemical Society,
Год журнала:
2022,
Номер
144(2), С. 963 - 976
Опубликована: Янв. 5, 2022
Cyclometalated
Ir(III)
complexes
are
often
chosen
as
catalysts
for
challenging
photoredox
and
triplet-triplet-energy-transfer
(TTET)
catalyzed
reactions,
they
of
interest
upconversion
into
the
ultraviolet
spectral
range.
However,
triplet
energies
commonly
employed
photosensitizers
typically
limited
to
values
around
2.5-2.75
eV.
Here,
we
report
on
a
new
luminophore,
with
an
unusually
high
energy
near
3.0
eV
owing
modification
previously
reported
complex
isocyanoborato
ligands.
Compared
nonborylated
cyanido
precursor
complex,
introduction
B(C6F5)3
units
in
second
coordination
sphere
results
substantially
improved
photophysical
properties,
particular
luminescence
quantum
yield
(0.87)
long
excited-state
lifetime
(13.0
μs),
addition
energy.
These
favorable
properties
(including
good
long-term
photostability)
facilitate
exceptionally
organic
photoreactions
(sensitized)
triplet-triplet
annihilation
fluorescent
singlet
excited
state
beyond
4
eV,
deep
region.
The
photocatalyzes
sigmatropic
shift
[2
+
2]
cycloaddition
reactions
that
unattainable
common
transition
metal-based
photosensitizers.
In
presence
sacrificial
electron
donor,
it
furthermore
is
applicable
demanding
photoreductions,
including
dehalogenations,
detosylations,
degradation
lignin
model
substrate.
Our
study
demonstrates
how
rational
ligand
design
transition-metal
underexplored
effects)
can
be
used
enhance
their
thereby
broaden
application
potential
solar
conversion
synthetic
photochemistry.
Journal of the American Chemical Society,
Год журнала:
2021,
Номер
144(1), С. 145 - 152
Опубликована: Дек. 30, 2021
The
positional
isomerization
of
C═C
double
bonds
is
a
powerful
strategy
for
the
interconversion
alkene
regioisomers.
However,
existing
methods
provide
access
to
thermodynamically
more
stable
isomers
from
less
starting
materials.
Here,
we
report
discovery
dual
catalyst
system
that
promotes
contra-thermodynamic
under
photochemical
irradiation,
providing
terminal
directly
conjugated,
internal
utility
method
demonstrated
in
deconjugation
diverse
electron-rich/electron-poor
alkenes
and
through
strategic
application
natural
product
synthesis.
Mechanistic
studies
are
consistent
with
regiospecific
bimolecular
homolytic
substitution
(SH2′)
mechanism
proceeding
an
allyl-cobaloxime
intermediate.
