49 research outputs found
Regioselective Pd-Catalyzed Aerobic Aza-Wacker Cyclization for Preparation of Isoindolinones and Isoquinolin-1(2<i>H</i>)-ones
A switchable regioselective intramolecular aerobic aza-Wacker cyclization catalyzed by palladium is presented. Isoindolinones or isoquinolin-1(2<i>H</i>)-ones could be prepared selectively from the same substrates using different catalysts. The type and steric hindrance of the ligands may be the variables most significant for regiocontrol
Iridium-Catalyzed Asymmetric Hydrogenation of β,γ-Unsaturated γ‑Lactams: Scope and Mechanistic Studies
An efficient asymmetric hydrogenation
of β,γ-unsaturated
γ-lactams using an iridium–phosphoramidite complex is
reported. The chiral γ-lactams were obtained in excellent yields
and enantioselectivities (up to 99% yield and 99% ee). The mechanistic
studies indicated that the reduced products were obtained via the
hydrogenation of the <i>N</i>-acyliminium cations, generated
from β,γ-unsaturated γ-lactams, which was verified
by <sup>1</sup>H NMR analysis. The reaction was carried out at a reduced
catalyst loading of 0.1 mol %, and the reduced products can be transformed
to two potential bioactive compounds. A new route is provided for
the synthesis of chiral γ-lactams
Synthesis of Chiral γ‑Lactams via in Situ Elimination/Iridium-Catalyzed Asymmetric Hydrogenation of Racemic γ‑Hydroxy γ‑Lactams
Chiral γ-lactams have been
synthesized in excellent yields
and enantioselectivities (up to 99% yield and 96% ee) from easily
accessible racemic γ-hydroxy γ-lactams via an iridium-phosphoramidite
catalyzed asymmetric hydrogenation. The reaction was designed based
on insight into the reaction mechanism demonstrated in previous work
and can be carried out at a reduced catalyst loading of 0.1 mol %
on a gram scale. Several potential bioactive compounds can be synthesized
from the reduced products. Mechanistic studies indicated that the
reduced products were obtained via the hydrogenation of the <i>N</i>-acyliminium cations, generated from γ-hydroxy γ-lactams
Pd(II)-Catalyzed Aerobic Intermolecular 1,2-Diamination of Conjugated Dienes: A Regio- and Chemoselective [4 + 2] Annulation for the Synthesis of Tetrahydroquinoxalines
A Pd(II)-catalyzed
aerobic intermolecular 1,2-diamination of conjugated
dienes was developed for the regio- and chemoselective preparation
of a variety of functionalized tetrahydroquinoxalines, using
simple sulfonyl protected <i>o</i>-phenylendiamines as a
nitrogen source. This methodology provides a direct and efficient
synthesis of tetrahydroquinoxalines. O<sub>2</sub> was used
as the stoichiometric oxidant, and reaction conditions were applied
to a series of <i>o</i>-phenylendiamines and conjugated
dienes. 35 examples are described, and good yields and selectivities
are obtained for the majority of the products
Pd(II)-Catalyzed Aerobic Intermolecular 1,2-Diamination of Conjugated Dienes: A Regio- and Chemoselective [4 + 2] Annulation for the Synthesis of Tetrahydroquinoxalines
A Pd(II)-catalyzed
aerobic intermolecular 1,2-diamination of conjugated
dienes was developed for the regio- and chemoselective preparation
of a variety of functionalized tetrahydroquinoxalines, using
simple sulfonyl protected <i>o</i>-phenylendiamines as a
nitrogen source. This methodology provides a direct and efficient
synthesis of tetrahydroquinoxalines. O<sub>2</sub> was used
as the stoichiometric oxidant, and reaction conditions were applied
to a series of <i>o</i>-phenylendiamines and conjugated
dienes. 35 examples are described, and good yields and selectivities
are obtained for the majority of the products
Pd(II)-Catalyzed Aerobic Intermolecular 1,2-Diamination of Conjugated Dienes: A Regio- and Chemoselective [4 + 2] Annulation for the Synthesis of Tetrahydroquinoxalines
A Pd(II)-catalyzed
aerobic intermolecular 1,2-diamination of conjugated
dienes was developed for the regio- and chemoselective preparation
of a variety of functionalized tetrahydroquinoxalines, using
simple sulfonyl protected <i>o</i>-phenylendiamines as a
nitrogen source. This methodology provides a direct and efficient
synthesis of tetrahydroquinoxalines. O<sub>2</sub> was used
as the stoichiometric oxidant, and reaction conditions were applied
to a series of <i>o</i>-phenylendiamines and conjugated
dienes. 35 examples are described, and good yields and selectivities
are obtained for the majority of the products
An Ir/Zn Dual Catalysis for Enantio- and Diastereodivergent α‑Allylation of α‑Hydroxyketones
An Ir/Zn dual catalysis has been
developed for the enantio- and
diastereodivergent α-allylation of unprotected α-hydroxyketones
under mild conditions, in the absence of any additional base. The
cooperative action of a chiral iridium complex derived from phosphoramidites
and a chiral Zn-ProPhenol complex is most likely responsible for its
high reactivity, excellent enantioselectivity (up to >99% ee),
and
good diastereoselectivity (up to >20:1 dr). All four product stereoisomers
could be prepared from the same set of starting materials and under
identical conditions by simple selection of appropriate catalyst combinations
An Ir/Zn Dual Catalysis for Enantio- and Diastereodivergent α‑Allylation of α‑Hydroxyketones
An Ir/Zn dual catalysis has been
developed for the enantio- and
diastereodivergent α-allylation of unprotected α-hydroxyketones
under mild conditions, in the absence of any additional base. The
cooperative action of a chiral iridium complex derived from phosphoramidites
and a chiral Zn-ProPhenol complex is most likely responsible for its
high reactivity, excellent enantioselectivity (up to >99% ee),
and
good diastereoselectivity (up to >20:1 dr). All four product stereoisomers
could be prepared from the same set of starting materials and under
identical conditions by simple selection of appropriate catalyst combinations
Synthesis of Chiral α,β-Unsaturated γ‑Amino Esters via Pd-Catalyzed Asymmetric Allylic Amination
A Pd-catalyzed
asymmetric allylic amination of 4-substituted 2-acetoxybut-3-enoates
with amines has been developed for the regiospecific synthesis of
chiral α,β-unsaturated γ-amino esters. The desired
chiral aminated products can be obtained in up to 98% yield, and 99%
ee and can be conveniently transformed to chiral γ-amino acid/alcohol
derivatives and chiral γ-lactams, which can then be subjected
to the synthesis of several types of chiral drugs and drug candidates.
The preferential formation of chiral γ-amino esters may be attributed
to the bulky substituents on the right side of the allyl substrates.
This work provides an efficient strategy for the synthesis of chiral
α,β-unsaturated γ-amino esters and their derivatives
Synthesis of Chiral α,β-Unsaturated γ‑Amino Esters via Pd-Catalyzed Asymmetric Allylic Amination
A Pd-catalyzed
asymmetric allylic amination of 4-substituted 2-acetoxybut-3-enoates
with amines has been developed for the regiospecific synthesis of
chiral α,β-unsaturated γ-amino esters. The desired
chiral aminated products can be obtained in up to 98% yield, and 99%
ee and can be conveniently transformed to chiral γ-amino acid/alcohol
derivatives and chiral γ-lactams, which can then be subjected
to the synthesis of several types of chiral drugs and drug candidates.
The preferential formation of chiral γ-amino esters may be attributed
to the bulky substituents on the right side of the allyl substrates.
This work provides an efficient strategy for the synthesis of chiral
α,β-unsaturated γ-amino esters and their derivatives