11 research outputs found
Catalytic Enantioselective Ring-Opening and Ring-Closing Reactions of 3‑Isothiocyanato Oxindoles and <i>N</i>‑(2-Picolinoyl)aziridines
3-Isothiocyanato oxindoles have been
successfully applied to an
asymmetric formal [3 + 3] cycloaddition reaction with aziridines for
the first time. The reaction was efficiently mediated by an in situ
generated magnesium catalyst employing (<i>R</i>)-3,3′-fluorous-BINOL
as a simple chiral ligand. Serials of polycyclic frameworks could
be obtained after a ring-closing step. The enantioenriched ring-opening
product was also utilized to modified amino acids, peptides, and bifunctional
organocatalyst
Catalytic Enantioselective Ring-Opening and Ring-Closing Reactions of 3‑Isothiocyanato Oxindoles and <i>N</i>‑(2-Picolinoyl)aziridines
3-Isothiocyanato oxindoles have been
successfully applied to an
asymmetric formal [3 + 3] cycloaddition reaction with aziridines for
the first time. The reaction was efficiently mediated by an in situ
generated magnesium catalyst employing (<i>R</i>)-3,3′-fluorous-BINOL
as a simple chiral ligand. Serials of polycyclic frameworks could
be obtained after a ring-closing step. The enantioenriched ring-opening
product was also utilized to modified amino acids, peptides, and bifunctional
organocatalyst
Catalytic Desymmetrization of <i>meso</i>-Aziridines with Benzofuran-2(3<i>H</i>)‑Ones Employing a Simple In Situ-Generated Magnesium Catalyst
The
first example of catalytic desymmetrization of <i>meso</i>-aziridines with benzofuran-2Â(3<i>H</i>)-ones is realized
by employing a magnesium catalyst utilizing BINOL as a simple and
commercially available chiral ligand. Both of the enantiomers of the
ring-opening product could be easily accessed by employing (<i>R</i>)- or (<i>S</i>)-BINOL as chiral ligand, respectively.
A variety of enantioenriched 3,3-disubstituted benzofuran-2Â(3<i>H</i>)-ones containing multiple linear continuous stereocenters
were obtained with moderate to good yields, diastereo- and enantioselectivities
Development and Application of α‑Heteroatom Ketones in Asymmetric Michael Reaction with β-<i>trans</i>-Nitroalkenes
The successful design and application
of a new type of <i>N</i>-phenyl-imidazole-modified α-heteroatom
ketones in
asymmetric <i>anti</i>-selective Michael reactions with
β-<i>trans</i>-nitroalkenes is reported. High yields
and enantioselectivities could be obtained, and the corresponding
conjugate adducts could be further transformed into related chiral
esters and cyclopropane derivatives with excellent enantioselectivities
Concerted Enantioselective [2+2] Cycloaddition Reaction of Imines Mediated by a Magnesium Catalyst
Enantioselective [2 + 2] cyclization between an imine
and a carbon–carbon
double bond is a versatile strategy to build chiral azetidines. However,
α-branched allenoates have never been successfully applied in
[2 + 2] cyclization reactions with imines, as they always undergo
Kwon’s [4 + 2] annulation in previous catalytic methods. Herein,
a simple in situ generated magnesium catalyst was employed to successfully
achieve the enantioselective [2 + 2] cyclization reaction of DPP-imines
and α-branched allenoates for the first time. Insightful experiments
including KIE experiments, controlled experiments, Hammett plot analysis,
and 31P NMR studies of initial intermediates indicate that
the current [2 + 2] cyclization of imine most likely involves an asynchronous
concerted transition state. Further mechanistic investigations by
combining kinetic studies, ESI experiments, 31P NMR studies
of coordination complexes, and controlled experiments on reaction
rates under different catalyst loading amounts provided the coordination
details for this [2 + 2] cyclization reaction between DPP-imines and
α-branched allenoates. This new approach was applied to the
synthesis of various chiral aza-heterocycles, including the enantioselective
synthesis of the key intermediate of a lipid-lowering agent Ezetimibe
Magnesium Catalysis Mediated Tetrazoles in Desymmetrization Reaction of Aziridines
A magnesium-catalyzed
asymmetric ring-opening reaction of aziridines
with substituted tetrazoles is reported. The current protocol proceeds
smoothly and gives the corresponding desymmetrization products in
high yields and good enantioselectivities. A new chiral ligand was
synthesized from azetidine and (<i>R</i>)-BINOL and was
employed in the current in situ generated magnesium catalyst. The
MgÂ(II)-mediated desymmetrization reaction could be performed on gram
scale under mild conditions and was transformed to chiral alkyl amines
by a deprotection process
Catalytic Asymmetric [3 + 2] Cyclization Reactions of 3‑Isothiocyanato Oxindoles and Alkynyl Ketones Via an in Situ Generated Magnesium Catalyst
A highly
enantioselective formal [3 + 2] cycloaddition reaction
between 3-isothiocyanato oxindoles and alkynyl ketones is reported
for the first time. An oxazoline–OH type chiral ligand derived
from <i>o</i>-hydroxy-phenylacetic acid is employed to generate
an effective magnesium catalyst in the current cyclization reaction
and give serials of chiral spirooxindoles with good chemical yields
and enantioselectivities
Correction to “Nickel-Mediated Asymmetric Allylic Alkylation between Nitroallylic Acetates and Acyl Imidazoles”
Correction to “Nickel-Mediated Asymmetric Allylic
Alkylation between Nitroallylic Acetates and Acyl Imidazoles
Correction to “Nickel-Mediated Asymmetric Allylic Alkylation between Nitroallylic Acetates and Acyl Imidazoles”
Correction to “Nickel-Mediated Asymmetric Allylic
Alkylation between Nitroallylic Acetates and Acyl Imidazoles
Development of ProPhenol/Ti(IV) Catalyst for Asymmetric Hydroxylative Dearomatization of Naphthols
By development of ProPhenol/Ti(IV) catalysts, a catalytic
enantioselective
hydroxylative dearomatization of naphthols is achieved by using TBHP
as a simple oxidative reagent. The side coordinative chain equipped
on the C1-position of β-naphthols plays an important role for
initiating this asymmetric hydroxylative reaction, which might be
a result of the proper cocoordination effects to the titanium center
in the catalyst. A reasonable catalytic cycle is proposed, the catalytic
system is applied to a reasonable range of this type of phenolic compound,
and related concise transformations are carried out