19 research outputs found
Tandem Blaise/Palladium-Catalyzed Ullmann Coupling for the One-Pot Synthesis of Enamino Ester-Functionalized Biaryls from Nitriles
A novel Pd-catalyzed Ullmann-type
homocoupling reaction of the
Blaise reaction intermediate generated by the reaction of 2-bromo
arylnitriles and a Reformatsky reagent has been developed for one-pot
synthesis of enamino ester-functionalized biaryls <b>2</b> in
good yields. The 2,2′-substituted enamine moieties of the coupling
products could be cyclized under acidic conditions through the conjugate
addition/deamination cascade to afford the seven-membered <i>N</i>-heterocyclics <b>3</b> with biaryl backbone in excellent
yields
Chemoselective Intramolecular Alkylation of the Blaise Reaction Intermediates: Tandem One-Pot Synthesis of <i>exo</i>-Cyclic Enaminoesters and Their Applications toward the Synthesis of <i>N</i>-Heterocyclic Compounds
The intramolecular alkylative reactivity and N/C selectivity
of
the various Blaise reaction intermediates, which are formed from the
reaction of the Reformatsky reagents with ω-chloroalkyl nitriles,
did not reach the synthetic potential as an entry to <i>exo</i>-cyclic enaminoesters. To circumvent this issue, various additives
were investigated, among which the addition of NaHMDS dramatically
enhanced the reactivity and N/C selectivity. This modification provided
a highly efficient route for the synthesis of various <i>N</i>-fused heterocyclic compounds, as it requires only two steps from
nitriles
Tandem Blaise/Palladium-Catalyzed Ullmann Coupling for the One-Pot Synthesis of Enamino Ester-Functionalized Biaryls from Nitriles
A novel Pd-catalyzed Ullmann-type
homocoupling reaction of the
Blaise reaction intermediate generated by the reaction of 2-bromo
arylnitriles and a Reformatsky reagent has been developed for one-pot
synthesis of enamino ester-functionalized biaryls <b>2</b> in
good yields. The 2,2′-substituted enamine moieties of the coupling
products could be cyclized under acidic conditions through the conjugate
addition/deamination cascade to afford the seven-membered <i>N</i>-heterocyclics <b>3</b> with biaryl backbone in excellent
yields
A Multifunction Pd/Sc(OTf)<sub>3</sub>/Ionic Liquid Catalyst System for the Tandem One-Pot Conversion of Phenol to ε‑Caprolactam
A multifunction
Pd/ScÂ(OTf)<sub>3</sub>/ionic liquid catalyst for
the tandem one-pot conversion of phenol to ε-caprolactam is
reported. Pd and ScÂ(OTf)<sub>3</sub> cooperate to catalyze the hydrogenation
of phenol to cyclohexanone with excellent conversion (>99.9%) and
selectivity (>99.9%), whereas ScÂ(OTf)<sub>3</sub> and an ionic
liquid,
[bmim]Â[PF<sub>6</sub>], cooperate to catalyze the tandem transformation
of the resulting cyclohexanone to cyclohexanone oxime and the Beckmann
rearrangement affording ε-caprolactam
An Expedient and Divergent Tandem One-Pot Synthesis of Pyrimidin-2,4-diones Using the Blaise Reaction Intermediate
A novel divergent tandem one-pot method for the synthesis of 3,5,6-trisubstituted 1<i>H</i>-pyrimidin-2,4-dione derivatives is developed. In the presence of 10 mol % of Cu(OAc)<sub>2</sub>, the α-substituted Blaise reaction intermediates (R<sup>2</sup> ≠H) reacted with isocyanates chemoselectively to afford pyrimidin-2,4-diones, whereas the α-unsubstituted Blaise reaction intermediate (R<sup>2</sup> = H) showed a propensity to be a C-nucleophile toward electrophiles, permitting the installation of different functionalities at the 5-position through sequential tandem reactions
Cu<sup>I</sup>/Rh<sup>II</sup>-Catalyzed Tandem Convergent Multicomponent Reaction for the Regio- and Stereocontrolled Synthesis of γ‑Oxo-β-amino Esters
The first example
of a highly regio- and stereoselective catalytic
method for the three-component one-pot synthesis of highly functionalized
α-vinylated γ-oxo-β-amino esters is disclosed. In
this catalytic triad, the Cu<sup>I</sup>-catalyst selectively catalyzes
the cycloaddition of the 1-alkyne and sulfonyl azide first resulting
in the corresponding 1-sulfonyl-1,2,3-triazole. An α-imino Rh<sup>II</sup>-carbene is generated from an open-chain α-imino diazo
of the triazole, and this species reacts with γ-hydroxy α,β-unsaturated
esters to form allylic (Z)-amino vinyl ethers. Rapid deconjugative
[3,3]-sigmatropic rearrangement affords the α-vinyl γ-oxo-β-amino
esters in high yields with high levels of diastereoselectivity
Pd-Catalyzed Aminocarbonylation of the Blaise Reaction Intermediate: One-Pot Synthesis of (<i>Z</i>)‑3-Methyleneisoindolin-1-ones from Nitriles
A highly
efficient method for the one-pot synthesis of stereocontrolled
(<i>Z</i>)-3-methyleneisoindolin-1-ones was developed starting
from 2-bromoarylnitriles via tandem sequential reaction with a Reformatsky
reagent (Blaise reaction), followed by Pd-catalyzed intramolecular
aminocarbonylation with carbon monoxide at 1 atm pressure. It has
been found that the conformational flexibility of the bisphophine
ligand is of great importance to the success of this tandem aminocarbonylation
reaction
An Expedient and Divergent Tandem One-Pot Synthesis of Pyrimidin-2,4-diones Using the Blaise Reaction Intermediate
A novel divergent tandem one-pot method for the synthesis of 3,5,6-trisubstituted 1<i>H</i>-pyrimidin-2,4-dione derivatives is developed. In the presence of 10 mol % of Cu(OAc)<sub>2</sub>, the α-substituted Blaise reaction intermediates (R<sup>2</sup> ≠H) reacted with isocyanates chemoselectively to afford pyrimidin-2,4-diones, whereas the α-unsubstituted Blaise reaction intermediate (R<sup>2</sup> = H) showed a propensity to be a C-nucleophile toward electrophiles, permitting the installation of different functionalities at the 5-position through sequential tandem reactions
Tandem One-Pot Synthesis of Polysubstituted NH-Pyrroles Involving the Palladium-Catalyzed Intramolecular Oxidative Amination of the Zinc Bromide Complex of β‑Enamino Esters
The Pd-catalyzed oxidative olefin
amination of the zinc bromide
complex intermediate, formed by the sequential reaction of nitriles
with a Reformatsky reagent and 1-alkynes, affords pyrrole derivatives
in good to excellent yields. This tandem protocol provides a simple,
efficient, and atom- and pot-economical way to quickly build polysubstituted
NH-pyrroles starting from readily available reagents in a regiocontrolled
manner with a broad substrate scope and high functional group tolerance.
In contrast, the Pd-catalyzed oxidative olefin amination of an isolated
α-vinyl-β-enamino ester did not proceed effectively, but
the reaction efficiency can be restored by addition of <i>n</i>-BuZnBr or ZnÂ(OAc)<sub>2</sub>, indicating the crucial role of the
zinc complex in this transformation. The synthetic utility of this
protocol is exemplified by the rapid synthesis of pyrrolophenanthrenes
and pyranopyrrolones through selective Pd- and Cu-catalyzed C–C
and C–O bond-forming reactions
DMF as a Source of Oxygen and Aminomethine: Stereoselective 1,2-Insertion of Rhodium(II) Azavinyl Carbenes into the Cî—»O Bond of Formamides for the Synthesis of <i>cis</i>-Diamino Enones
A new catalytic reaction in which
all the atoms of a formamide
are incorporated into the product through a formal stereoselective
1,2-insertion of rhodiumÂ(II) azavinyl carbenes, generated in situ
from readily available <i>N</i>-sulfonylated 1,2,3-triazoles,
into the Cî—»O bond of DMF and other <i>N</i>,<i>N</i>-disubstituted formamides to afford <i>cis</i>-diamino enones is described