10 research outputs found
Pd(II)/Brønsted Acid Catalyzed Enantioselective Allylic C–H Activation for the Synthesis of Spirocyclic Rings
A PdÂ(II)/Brønsted acid catalyzed migratory ring
expansion
for the synthesis of indene derivatives possessing a stereogenic spirocyclic
carbon center was developed. This transformation is believed to mechanistically
proceed via enantioselective allylic C–H activation with concomitant
semipinacol ring expansion to the nascent π-allylpalladium species.
Enantioselectivities as high as 98% ee were attainable
Phosphine Catalyst-Controlled Cycloaddition or Dienylation Reactions of Trifluoromethyl Aryl Ketones with Bis-Substituted Allenoates
A chemoselective
phosphine-catalyzed cycloaddition or dienylation
reaction between trifluoromethyl-substituted ketones and bis-substituted
allenoates was described. Under the catalysis of triarylphosphine,
the reaction gave a range of trifluoromethylated tetrahydrofurans
with broad substrate tolerance and good to excellent stereoselectivity,
while the use of trialkylphosphine switched the reaction pathway to
furnish CF<sub>3</sub>-substituted dienyl tertiary alcohols chemoselectively.
Moreover, a preliminary study on the asymmetric version of the reaction
was also performed, which represents the first example of a phosphine-catalyzed
asymmetric reaction between allenoates and carbonyl compounds
FeCl<sub>3</sub>‑Promoted [3 + 2] Annulations of γ‑Butyrolactone Fused Cyclopropanes with Heterocumulenes
The
[3 + 2] annulations of γ-butyrolactone fused donor–acceptor
(D–A) cyclopropanes with aromatic isothiocyanates and dialkyl
carbodiimides promoted by FeCl<sub>3</sub> is reported. A series of
bicyclic/polycyclic Îł-butyrolactone fused thioimidates and Îł-butyrolactone
fused amidines containing four contiguous stereogenic centers were
obtained in excellent yields as single stereoisomers
Lewis Acid-Catalyzed Annulations of Geminally Disubstituted Cyclopropanes with Aldehydes or 1,3,5-Triazinanes
Under the catalysis of simple Lewis acid catalysts, 2-(1-aroylcyclopropyl)malonates
demonstrated unique reactivities in annulation reactions with aryl/alkyl
aldehydes, paraformaldehyde, and 1,3,5-triazinanes. Three types of
structurally diverse cyclic products that are otherwise not easy to
obtain were generated in moderate to good yields and excellent diastereoselectivities.
Possible reaction pathways leading to these products were proposed
on the basis of the results of control experiments
<i>cis</i>-2,3-Disubstituted Cyclopropane 1,1-Diesters in [3 + 2] Annulations with Aldehydes: Highly Diastereoselective Construction of Densely Substituted Tetrahydrofurans
A series of <i>cis</i>-2,3-disubstituted
cyclopropane
1,1-diesters were examined in the AlCl<sub>3</sub>-promoted [3 + 2]-annulations
with aldehydes. In this reaction, these <i>cis</i>-cyclopropanes
displayed reactivities starkly different from their <i>trans</i> counterparts in terms of the high chemical yields (up to 98%) and
provided the desired annulation products with excellent diastereomeric
purity. This protocol provides a facile and highly stereoselective
way to construct synthetically useful pentasubstituted tetrahydrofurans
not easily accessible using other methods
<i>cis</i>-2,3-Disubstituted Cyclopropane 1,1-Diesters in [3 + 2] Annulations with Aldehydes: Highly Diastereoselective Construction of Densely Substituted Tetrahydrofurans
A series of <i>cis</i>-2,3-disubstituted
cyclopropane
1,1-diesters were examined in the AlCl<sub>3</sub>-promoted [3 + 2]-annulations
with aldehydes. In this reaction, these <i>cis</i>-cyclopropanes
displayed reactivities starkly different from their <i>trans</i> counterparts in terms of the high chemical yields (up to 98%) and
provided the desired annulation products with excellent diastereomeric
purity. This protocol provides a facile and highly stereoselective
way to construct synthetically useful pentasubstituted tetrahydrofurans
not easily accessible using other methods
A Novel Lewis Acid Catalyzed [3 + 3]-Annulation Strategy for the Syntheses of Tetrahydro-β-Carbolines and Tetrahydroisoquinolines
A novel Lewis acid catalyzed [3 + 3]-annulation process for the efficient syntheses of both tetrahydro-β-carbolines and tetrahydroisoquinolines from readily available benzylic alcohols and aziridines was developed, which would be a highly valuable complement to the widely used Pictet–Spengler reaction. A probable mechanism was proposed based on the isolation and characterization of two key intermediates. This strategy enables facile access to important alkaloid frameworks not easily available with other known methods
Lewis Acid Catalyzed Cascade Reaction to Carbazoles and Naphthalenes via Dehydrative [3 + 3]-Annulation
A novel Lewis acid catalyzed dehydrative
[3 + 3]-annulation of
readily available benzylic alcohols and propargylic alcohols was developed
to give polysubstituted carbazoles and naphthalenes in moderate to
good yields with water as the only byproduct. The reaction was presumed
to proceed via a cascade process involving Friedel–Crafts-type
allenylation, 1,5-hydride shift, 6π-eletrocyclization, and Wagner–Meerwein
rearrangement
Copper(I)-Catalyzed Kinetic Resolution of <i>N</i>‑Sulfonylaziridines with Indoles: Efficient Construction of Pyrroloindolines
The first Lewis acid
catalyzed [3 + 2] annulation of indoles and
2-aryl-<i>N</i>-tosylaziridines was realized by using copperÂ(I)/chiral
diphosphine complexes as a catalyst. With this method, a variety of
uniquely substituted chiral pyrroloindolines bearing multiple contiguous
stereogenic centers were facilely accessed in a straightforward, high-yielding,
and highly stereoselective way under mild conditions
Indolyl-based Copper(I) Complex-Catalyzed Intermolecular Trifluoromethylazolation of Alkenes via Radical Process
Herein,
we synthesized and characterized a binuclear copper(I)
complex supported by the indolyl-based ligand. Employing this complex
as catalyst, we have developed a three-component intermolecular trifluoromethylazolation
of alkenes to deliver various trifluoromethylated azole derivatives.
The method features exclusive chemo- and regioselectivity, a broad
scope of alkenes and oxazoles, thiazoles, and good tolerance of functional
groups under mild conditions. Preliminary mechanistic studies support
a radical process for the transformation