6 research outputs found
Catalytic Asymmetric Synthesis of Chiral γ‑Amino Ketones via Umpolung Reactions of Imines
The
first direct catalytic asymmetric synthesis of γ-amino
ketones was realized by the development of a highly diastereoselective
and enantioselective C–C bond-forming umpolung reaction of
imines and enones under the catalysis of a new cinchona alkaloid-derived
phase-transfer catalyst. In a loading ranging from 0.02 to 2.5 mol
%, the catalyst activates a broad range of trifluoromethyl imines
and aldimines as nucleophiles to engage in chemo-, regio-, diastereo-
and enantioselective C–C bond-forming reactions with acyclic
and cyclic enones, thereby converting these readily available prochiral
starting materials into highly enantiomerically enriched chiral γ-amino
ketones in synthetically useful yields. Enabled by this unprecedented
umpolung reaction of imines, conceptually new and concise routes were
developed for the asymmetric synthesis of nitrogen-heterocycles such
as pyrrolidines and indolizidines
Catalytic Asymmetric Synthesis of Chiral γ‑Amino Ketones via Umpolung Reactions of Imines
The
first direct catalytic asymmetric synthesis of γ-amino
ketones was realized by the development of a highly diastereoselective
and enantioselective C–C bond-forming umpolung reaction of
imines and enones under the catalysis of a new cinchona alkaloid-derived
phase-transfer catalyst. In a loading ranging from 0.02 to 2.5 mol
%, the catalyst activates a broad range of trifluoromethyl imines
and aldimines as nucleophiles to engage in chemo-, regio-, diastereo-
and enantioselective C–C bond-forming reactions with acyclic
and cyclic enones, thereby converting these readily available prochiral
starting materials into highly enantiomerically enriched chiral γ-amino
ketones in synthetically useful yields. Enabled by this unprecedented
umpolung reaction of imines, conceptually new and concise routes were
developed for the asymmetric synthesis of nitrogen-heterocycles such
as pyrrolidines and indolizidines
Copper-Catalyzed Electrophilic Polyhydroamination of Internal Alkynes
Polyhydroamination of alkynes is
an important methodology for preparing
nitrogen-containing polymers. At present, all of the reported polyhydroamination
of alkynes proceed through nucleophilic addition, and no straightforward
electrophilic polyhydroamination has been reported. In this paper,
a novel copper-catalyzed electrophilic polyhydroamination of alkynes
was developed, and soluble and thermally stable polyÂ(enamine)Âs with
high weight-average molecular weights (<i>M</i><sub>w</sub>s, up to 12 650) were produced in excellent yields (up to
95%) under mild reaction conditions. Moreover, the regioselectivity
of this electrophilic polyhydroamination could be tuned by adjusting
one of the substitutions of internal diynes from phenyl to alkyl group.
By introducing the tetraphenylethene moiety into polymer backbones,
the resultant polymers exhibit unique aggregation-induced emission
feature, and their aggregates could be used to sensitively detect
explosives. This efficient polymerization will open up enormous opportunities
for preparing functional nitrogen-containing acetylenic polymers applicable
in diverse areas
Pd-Catalyzed γ‑C(sp<sup>3</sup>)–H Arylation of Free Amines Using a Transient Directing Group
PdÂ(II)-catalyzed
γ-CÂ(sp<sup>3</sup>)–H arylation of
primary amines is realized by using 2-hydroxyÂnicotinaldehyde
as a catalytic transient directing group. Importantly, the catalyst
and the directing group loading can be lowered to 2% and 4% respectively,
thus demonstrating high efficiency of this newly designed transient
directing group. Heterocyclic aryl iodides are also compatible with
this reaction. Furthermore, swift synthesis of 1,2,3,4-tetrahydroÂnaphthyridine
derivatives is accomplished using this reaction
Versatile Alkylation of (Hetero)Aryl Iodides with Ketones via β‑C(sp<sup>3</sup>)–H Activation
We
report PdÂ(II)-catalyzed β-CÂ(sp<sup>3</sup>)–H (hetero)ÂarylÂation
of a variety of ketones using a commercially available 2,2-dimethyl
aminoÂoxyÂacetic acid auxiliary. Facile installation and
removal of the auxiliary as well as its superior scope for both ketones
and (hetero)Âaryl iodides overcome the significant limitations
of the previously reported β-CÂ(sp<sup>3</sup>)–H arylation
of ketones. The ready availability of ketones renders this reaction
a broadly useful method for alkyl–(hetero)Âaryl coupling
involving both primary and secondary alkyls
Spontaneous Amino-yne Click Polymerization: A Powerful Tool toward Regio- and Stereospecific Poly(β-aminoacrylate)s
Efficient synthesis of polyÂ(enamine)Âs
has been a great challenge
because of their poor stability, poor solubility, and low molecular
weights. In this work, a spontaneous amino-yne click polymerization
for the efficient preparation of polyÂ(enamine)Âs was established, which
could proceed with 100% atom efficiency under very mild conditions
without any external catalyst. Through systematic optimization of
the reaction conditions, several soluble and thermally stable polyÂ(β-aminoacrylate)Âs
with high molecular weights (<i>M</i><sub>w</sub> up to
64400) and well-defined structures were obtained in excellent yields
(up to 99%). Moreover, the polymerization can perform in a regio-
and stereospecific fashion. Nuclear magnetic resonance spectra analysis
revealed that solely anti-Markovnikov additive products with 100% <i>E</i>-isomer were obtained. The reaction mechanism was well
demonstrated with the assistance of density functional theory calculations.
In addition, by introducing the tetraphenylethene moiety, the resulting
polymers exhibit unique aggregation-induced emission characteristics
and could be applied in explosives detection and bioimaging. This
polyhydroamination is a new type of click polymerization and opens
up enormous opportunities for preparing functional polymeric materials