Visible Light-Promoted Deracemization of α-Amino Aldehyde by Synergistic Chiral Primary Amine and Hypervalent Iodine Catalysis
Journal of the American Chemical Society,
Год журнала:
2025,
Номер
unknown
Опубликована: Фев. 6, 2025
α-Amino
aldehydes,
as
versatile
chiral
synthons,
are
easily
racemized
under
normal
acid
or
base
conditions,
seriously
limiting
their
synthetic
potentials.
We
report
herein
an
effective
deracemization
of
α-amino
aldehydes
by
a
synergistic
primary
amine
and
hypervalent
iodine
catalysis
visible
light.
The
developed
catalytic
system
allows
for
the
on-demand
production
α-Boc-
Cbz-protected
amino
with
high
enantioselectivity.
Mechanistic
studies
verified
photochemical
Z-E
isomerization
mechanism
that
drives
process.
Язык: Английский
Stereochemical Editing at sp3-Hybridized Carbon Centers by Reversible, Photochemically Triggered Hydrogen Atom Transfer
Accounts of Chemical Research,
Год журнала:
2025,
Номер
unknown
Опубликована: Фев. 19, 2025
ConspectusMillions
of
chiral
compounds
contain
a
stereogenic
sp3-hybridized
carbon
center
with
hydrogen
atom
as
one
the
four
different
substituents.
The
can
be
edited
in
an
increasing
number
cases
by
selective
transfer
(HAT)
to
and
from
photocatalyst.
This
Account
describes
development
photochemical
deracemization
reactions
using
oxazole-annulated
benzophenones
bonding
motif
that
allows
them
recognize
lactam
substrates
two-point
bonding.
backbone
catalysts
consists
azabicyclo[3.3.1]nonan-2-one
U-shaped
geometry,
which
enables
substrate
recognition
occur
parallel
benzoxazole
part
aromatic
ketones.
photocatalysts
facilitate
catalytic
several
compound
classes
including
hydantoins,
N-carboxyanhydrides,
oxindoles,
2,5-diketopiperazines,
4,7-diaza-1-isoindolinones.
In
addition,
if
more
than
is
present,
editing
delivers
distinct
diastereoisomer
upon
appropriate
selection
respective
photocatalyst
enantiomer.
operate
via
benzophenone
triplet
selectively
abstracts
properly
positioned
exclusively
two
enantiomers.
step
creates
planar
carbon-centered
radical
erases
absolute
configuration
at
this
position.
While
returning
HAT
same
position
would
likely
recreate
configuration,
spectroscopic
quantum
chemical
studies
suggest
delivered
heteroatom
conjugation
center.
Two
scenarios
distinguished
for
shuttling
process.
For
4,7-diaza-1-isoindolinones,
back
occurs
carbonyl
oxygen
or
imine-type
nitrogen
not
involved
binding
catalyst.
oxindoles
single
group
available
accept
atom.
It
currently
assumed
group,
although
comparison
former
reaction
pathway,
latter
process
appears
less
efficient
prone
side
reactions.
both
cases,
achiral
enol
enamine
formed,
dissociation
catalyst
statistically
either
stereoisomers
substrate.
Since
only
enantiomer
(or
diastereoisomer)
processed,
high
enantioselectivity
diastereoselectivity)
results.
Even
though
contra-thermodynamic
process,
described
decoupling
thermal
usage
loadings
vary
between
2.5
10
mol
%
depending
on
specific
mode
action.
Язык: Английский
Enantioselective Hydrodifluoroalkylation of Alkenes with Conformationally Tuned Peptidyl Hydrogen Atom Transfer Catalysts
Journal of the American Chemical Society,
Год журнала:
2025,
Номер
unknown
Опубликована: Март 20, 2025
We
report
the
enantioselective
hydrodifluoroalkylation
of
alkenes
proceeding
via
an
asymmetric
hydrogen
atom
transfer
(HAT)
event
catalyzed
by
thiol-containing
tetrapeptides.
Photocatalytic
generation
a
difluoroacetyl
radical
followed
carbon–carbon
bond
formation
results
in
prochiral
carbon-centered
that
engages
with
chiral
catalyst.
A
trialkylamine
reductant
is
proposed
to
turn
over
catalyst
this
net-reductive
transformation.
Notably,
incorporating
(S)-β-methyl-substituted
cysteine
as
N-terminal
residue
improved
selectivity
relative
native
(Cys)
residue,
and
X-ray
crystallographic
analysis
supports
conformational
underpinning
effect.
range
enantioenriched
γ-substituted
amides
were
synthesized
up
96:4
enantiomeric
ratio,
demonstrating
broad
functional
group
tolerance
method.
Models
accounting
for
induction
are
supporting
DFT
calculations.
Язык: Английский
Photocatalyst-Dependent Enantioselectivity in the Light-Driven Deracemization of Cyclic α-Aryl Ketones
Journal of the American Chemical Society,
Год журнала:
2025,
Номер
unknown
Опубликована: Апрель 22, 2025
We
report
a
photoredox-enabled
deracemization
of
cyclic
α-aryl
ketones
that
occurs
with
high
stereoselectivity
and
yield
proceeds
by
mechanistically
distinct
proton
transfer
reactions.
This
reaction
is
jointly
mediated
visible-light
photocatalyst
chiral
phosphate
base
cocatalyst
under
blue
light
irradiation.
Notably,
the
extent
for
this
exhibits
an
unexpected
dependence
on
identity
concentration
cocatalyst,
wherein
can
be
increased
employing
photocatalysts
more
positive
ground-state
reduction
potentials,
raising
or
combination
these
factors.
effect
attributed
to
two
competing
processes,
back-electron
deprotonation,
which
consume
same
intermediate,
we
propose
kinetic
model
rationalizes
behavior.
also
demonstrate
redox
properties
impact
product-forming
step,
dominant
stereoselective
step
in
transformation.
Together,
mechanistic
insights
facilitate
deeper
understanding
complexity
light-driven
reactions
involving
reversible
electron
suggest
approaches
processes
may
increased.
Язык: Английский