15 research outputs found
Rh/SPO-WudaPhos-Catalyzed Asymmetric Hydrogenation of α‑Substituted Ethenylphosphonic Acids via Noncovalent Ion-Pair Interaction
Asymmetric hydrogenation
of α-substituted ethenylphosphonic acids has been successfully
achieved by Rh/ferrocenyl chiral bisphosphorus ligand (SPO-Wudaphos)
through noncovalent ion-pair interaction between the substrate and
catalyst under mild reaction conditions without base. A series of
chiral phosphonic acids were obtained with excellent results (up to
98% ee, >99% conversion, 2000 TON). Moreover, the control experiments
showed that the noncovalent ion-pair interaction was critical in this
asymmetric hydrogenation
Catalytic Asymmetric Desymmetrization of Cyclopentendiones via Diels–Alder Reaction of 3‑Hydroxy-2-pyrones: Construction of Multifunctional Bridged Tricyclic Lactones
An unprecedented asymmetric Diels–Alder
reaction of 3-hydroxy-2-pyrones
with prochiral cyclopentene-1,3-diones via desymmetrization was efficiently
realized with high stereoselective control with the aid of fine-tunable
cinchona alkaloid derived bifunctional amine–thiourea catalysts
bearing multiple hydrogen-bonding donors. This protocol provides an
expedient access to the multifunctional-bridged tricyclic lactones
featuring four contiguous stereogenic centers and one remote quaternary
stereogenic center with a broad substrate scope. The cycloadduct can
be readily elaborated into enantioenriched cyclopentane-1,3-diones
via ring opening/aromatization
Selective Rhodium-Catalyzed Hydroformylation of Alkynes to α,β-Unsaturated Aldehydes with a Tetraphosphoramidite Ligand
A tetraphosphoramidite
ligand was successfully applied to a Rh-catalyzed
hydroformylation of various symmetrical and unsymmetrical alkynes
to afford corresponding α,β-unsaturated aldehyde products
in good to excellent yields (up to 97% yield). Excellent chemo- and
regioselectivities and high activities (up to 20 000 TON) were
achieved. The corresponding α,β-unsaturated aldehyde products
can be transformed into many useful and important organic molecules,
such as indenamine derivatives and lukianol pyrroles. This great performance
makes the hydroformylation of alkynes highly practical with great
potential
Ni-Catalyzed Asymmetric Hydrogenation of α‑Substituted α,β-Unsaturated Phosphine Oxides/Phosphonates/Phosphoric Acids
Efficient Ni/(S,S)-Ph-BPE-catalyzed
asymmetric hydrogenation of α-substituted α,β-unsaturated
phosphine oxides/phosphonates/phosphoric acids has been successfully
developed, and a wide range of chiral α-substituted phosphines
hydrogenation products were obtained in generally high yields with
excellent enantioselective control (92%–99% yields, 84%−>99% ee). This method features a cheap
transition metal nickel catalytic system, high functional group tolerance,
wide substrate scope generality, and excellent enantioselectivity.
A plausible catalytic cycle was proposed for this asymmetric hydrogenation
according to the results of deuterium-labeling experiments
Synthesis of Chiral β‑Amino Nitroalkanes via Rhodium-Catalyzed Asymmetric Hydrogenation
The asymmetric hydrogenation
of β-amino nitroolefins has
been successfully achieved by rhodium/bisÂ(phosphine)-thiourea <b>L</b><sub><b>1</b></sub> with excellent enantioselectivities
and yields (up to 96% ee, 96% yield, >99% conversion, TON up to
1000)
under mild conditions. Chiral β-amino nitroalkane products and
their derivatives are versatile intermediates in organic synthesis
Highly Enantioselective Synthesis of Chiral Succinimides via Rh/Bisphosphine-Thiourea-Catalyzed Asymmetric Hydrogenation
We have successfully developed a
highly enantioselective hydrogenation
of various 3-aryl and 3-methyl maleinimides to access enantiomerically
pure 3-substituted succinimides catalyzed by Rh/bisphosphine-thiourea
(ZhaoPhos). This efficient catalytic system furnished the desired
3-substituted succinimide products with high yields and enantioselectivities
(up to 99% yield, full conversions, almost all 3-aryl succinimide
products up to 99% ee, and 3-methyl succinimide with 83% ee). Our
catalytic system has a strong substrate tolerance and generality.
Whether the N-substituted group of maleinimides is H or other protecting
groups, the maleinimides were hydrogenated well (up to >99% ee,
99%
yield). Moreover, the hydrogenation succinimide products can be readily
utilized for the construction of biologically active molecules, such
as chiral amides and pyrrolidines
Metal-Free Etherification of Aryl Methyl Ether Derivatives by C–OMe Bond Cleavage
A general and efficient
protocol was developed for the synthesis
of aryl alkyl ethers through metal-free C–OMe bond cleavage
under mild reaction conditions. This process displays a wide scope
of methoxyarenes and alcohols, including primary, secondary, and tertiary
alcohols, as well as natural products, pharmaceuticals, and biologically
active alcohols. DFT calculations and experimental results simultaneously
confirm that a potassium ion plays a critical role in the activation
of methoxy group via binding with the nitrile and provide support
for an S<sub>N</sub>Ar mechanism
Highly Enantioselective Asymmetric Hydrogenation of Carboxy-Directed α,α-Disubstituted Terminal Olefins via the Ion Pair Noncovalent Interaction
The <i>t</i>-Bu-Wudaphos was successfully applied into
Rh-catalyzed asymmetric hydrogenation of α,α-disubstituted
terminal olefins bearing a carboxy-directed group with excellent reactivities
and enantioselectivities via the ion pair noncovalent interaction
(up to >99% conversion, 98% yield, 98% ee) under mild reaction
conditions
without base. In addition, control experiments were conducted, and
the results demonstrated that the ion pair noncovalent interaction
between ligand and substrate played an important role in achieving
an outstanding performance in this asymmetric hydrogenation