11 research outputs found
Iridium-Catalyzed Highly Regioselective Azide–Ynamide Cycloaddition to Access 5‑Amido Fully Substituted 1,2,3-Triazoles under Mild, Air, Aqueous, and Bioorthogonal Conditions
A highly
regioselective method to access 5-amido fully substituted
1,2,3-triazoles by iridium-catalyzed azide–ynamide cycloaddition
under mild, air, aqueous, and bioorthogonal conditions is reported.
The excellent regioselectivities may derive from the strong coordination
between the carbonyl oxygen of ynamide and the π-acidic iridium.
Since the iridium ion is insensitive to oxygen/water and exhibits
low cytotoxicity, it could catalyze this reaction in both organic
and biological environments efficiently. Preparation in gram-scale
and application in carbohydrates highlight this method
Rhodium-Catalyzed Tandem Annulation and (5 + 1) Cycloaddition: 3‑Hydroxy-1,4-enyne as the 5‑Carbon Component
A Rh-catalyzed
tandem annulation and (5 + 1) cycloaddition was
realized. 3-Hydroxy-1,4-enyne served as the new 5-carbon component
for the (5 + 1) cycloaddition.
Substituted carbazoles, dibenzofurans, and tricyclic compounds containing
a cyclohexadienone moiety could be prepared efficiently. The identification
of a byproduct suggests that metal carbene and ketene intermediates
may be involved in the (5 + 1) cycloaddition
Gold-Catalyzed <i>Anti</i>-Markovnikov Oxidation of Au-Allenylidene to Generate Alkylidene Ketene
It remains a long-standing challenge to directly convert
alkynes
to carboxylic derivatives. Herein, a unexpectedly anti-Markovnikov oxidation of a unique Au-allenylidene pathway instead
of a traditional α-oxo gold carbene routine is disclosed for in situ formation and transformation of highly unsaturated
alkylidene ketenes, which are subsequently trapped by broad nucleophiles
such as alcohols, phenols, water, amines, and sulfoximines to easily
access α,β-unsaturated drugs and natural
product derivatives by a multicomponent reaction. Based on this scenario,
polyacrylate and polyacrylamide are efficiently afforded by corresponding
multicomponent polymerization
α‑Aryl-Substituted Allenamides in an Imino-Nazarov Cyclization Cascade Catalyzed by Au(I)
An imino-Nazarov cyclization using α-aryl-substituted allenamides is described. This gold(I)-catalyzed cascade is efficient and regioselective in constructing a diverse array of synthetically useful aromatic-ring fused cyclopentenamides. The success in this transformation represents a solution to the challenge in establishing an imino-Nazarov cyclization process
α‑Aryl-Substituted Allenamides in an Imino-Nazarov Cyclization Cascade Catalyzed by Au(I)
An imino-Nazarov cyclization using α-aryl-substituted allenamides is described. This gold(I)-catalyzed cascade is efficient and regioselective in constructing a diverse array of synthetically useful aromatic-ring fused cyclopentenamides. The success in this transformation represents a solution to the challenge in establishing an imino-Nazarov cyclization process
α‑Aryl-Substituted Allenamides in an Imino-Nazarov Cyclization Cascade Catalyzed by Au(I)
An imino-Nazarov cyclization using α-aryl-substituted allenamides is described. This gold(I)-catalyzed cascade is efficient and regioselective in constructing a diverse array of synthetically useful aromatic-ring fused cyclopentenamides. The success in this transformation represents a solution to the challenge in establishing an imino-Nazarov cyclization process
Rhodium-Catalyzed Highly Regioselective and Stereoselective Intermolecular Hydrosilylation of Internal Ynamides under Mild Conditions
A rhodium-catalyzed highly regio-
and stereoselective intermolecular
hydrosilylation of internal ynamides has been developed. With the
neutral rhodium complex [RhÂ(CO)<sub>2</sub>Cl]<sub>2</sub> as a catalyst
and the bulky silanes as reactants, various ynamides underwent hydrosilylation
smoothly at room temperature with an excellent β-regioselectivity
and <i>anti</i>-stereoselectivity. The synthetically versatile
β-silyl (<i>Z</i>)-enamide products could be further
transformed to diverse useful building blocks. Several possible mechanisms
are proposed to rationalize this unique formal <i>trans</i>-addition-type selectivity
Enantioselective α‑Hydroxylation by Modified Salen-Zirconium(IV)-Catalyzed Oxidation of β‑Keto Esters
The
highly enantioselective α-hydroxylation of β-keto
esters using cumene hydroperoxide (CHP) as the oxidant was realized
by a chiral (1<i>S</i>,2<i>S</i>)-cycloÂhexaneÂdiamine
backbone salen-zirconiumÂ(IV) complex as the catalyst. A variety of
corresponding chiral α-hydroxy β-keto esters were obtained
in excellent yields (up to 99%) and enantioÂselectivities (up
to 98% ee). The zirconium-catalyzed enantioselective α-hydroxylation
of β-keto esters was scalable, and the zirconium catalyst was
recyclable. The reaction can be performed in gram scale, and corresponding
chiral products were acquired in 95% yield and 99% ee
Synthesis of Carbazoles and Carbazole-Containing Heterocycles via Rhodium-Catalyzed Tandem Carbonylative Benzannulations
Polycyclic
aromatic compounds are important constituents of pharmaceuticals
and other materials. We have developed a series of Rh-catalyzed tandem
carbonylative benzannulations for the synthesis of tri-, tetra-, and
pentacyclic heterocycles from different types of aryl propargylic
alcohols. These tandem reactions provide efficient access to highly
substituted carbazoles, furocarbazoles, pyrrolocarbazoles, thiophenocarbazoles,
and indolocarbazoles. While tricyclic heterocycles could be derived
from vinyl aryl propargylic alcohols, tetra- and pentacyclic heterocycles
were synthesized from diaryl propargylic alcohols. The tandem carbonylative
benzannulation is initiated by a Ï€-acidic rhodiumÂ(I) catalyst-mediated
nucleophilic addition to alkyne to generate a key metal-carbene intermediate,
which is then trapped by carbon monoxide to form a ketene species
for 6Ï€ electrocyclization. Overall, three bonds and two rings
are formed in all of these tandem carbonylative benzannulation reactions
Rhodium-Catalyzed Stereoselective Intramolecular [5 + 2] Cycloaddition of 3‑Acyloxy 1,4-Enyne and Alkene
The
first rhodium-catalyzed intramolecular [5 + 2] cycloaddition
of 3-acyloxy 1,4-enyne and alkene was developed. The cycloaddition
is highly diastereoselective in most cases. Various <i>cis</i>-fused bicyclo[5.3.0]Âdecadienes were prepared stereoselectively.
The chirality in the propargylic ester starting materials could be
transferred to the bicyclic products with high efficiency. Electron-deficient
phosphine ligand greatly facilitated the cycloaddition. Up to three
new stereogenic centers could be generated. The resulting diene in
the products could be hydrolyzed to enones, which allowed the introduction
of more functional groups to the seven-membered ring