150 research outputs found
NHC–AuCl/Selectfluor: A Highly Efficient Catalytic System for Carbene-Transfer Reactions
The combination of NHC–gold
complex and Selectfluor has
been found to be a highly efficient catalyst system for carbene-transfer
reactions, with a turnover number (TON) up to 990000 and a turnover
frequency (TOF) up to 82500 h<sup>–1</sup>
Ruthenium-Catalyzed Dehydrogenative β‑Benzylation of 1,2,3,4-Tetrahydroquinolines with Aryl Aldehydes: Access to Functionalized Quinolines
A new
benzylation protocol, enabling straightforward access to
β-benzylated quinolines, has been demonstrated. By employing
readily available [RuCl<sub>2</sub>(<i>p</i>-cymene)]<sub>2</sub> as a catalyst and O<sub>2</sub> as a sole green oxidant,
various 1,2,3,4-tetrahydroÂquinolines were efficiently converted
in combination with aryl aldehydes into desired products in a step-
and atom-economic fashion together with the advantages of excellent
functional group tolerance and chemoselectivity, offering an important
basis for the transformation of saturated <i>N</i>-heterocycles
into functionalized <i>N</i>-heteroaromatics via a dehydrogenative
cross-coupling strategy. Mechanistic investigations support that the
reaction undergoes a monodehydrogenation-triggered β-benzylation
mode
Access to C(sp<sup>3</sup>)–C(sp<sup>2</sup>) and C(sp<sup>2</sup>)–C(sp<sup>2</sup>) Bond Formation via Sequential Intermolecular Carbopalladation of Multiple Carbon–Carbon Bonds
A synthetic strategy of 4-benzyl-substituted 1,3-butadiene
derivatives
through Pd-catalyzed three-component coupling reaction of benzyl chlorides,
alkynes, and monosubstituted alkenes is described. This tandem coupling
reaction forms a CÂ(sp<sup>3</sup>)–CÂ(sp<sup>2</sup>) bond and
a CÂ(sp<sup>2</sup>)–CÂ(sp<sup>2</sup>) bond sequentially in
a single-step operation
Cu(II)-Catalyzed Synthesis of Naphthalene-1,3-diamine Derivatives from Haloalkynes and Amines
An efficient procedure for the preparation of naphthalene-1,3-diamine derivatives by copper-catalyzed haloalkynes with amines has been reported. The reaction was supposed to proceed through a coupling reaction followed by the dimerization of ynamines
Ruthenium-Catalyzed C–H Arylation of Aromatic Acids with <i>ortho</i>-Haloaniline To Access Phenanthridinones
Phenanthridinone is a significant
moiety in pharmaceutical and
material science; thus, it is highly desirable to develop an efficient
and robust method to construct phenanthridinone from readily available
starting materials. Herein, we report a Ru-catalyzed C–H arylation
of aromatic carboxylic acids with ortho-haloanilines,
followed by intramolecular dehydration to afford phenanthridinones
in high yields
Synthesis of γ‑Thiapyrones by Diels–Alder/Retro-Diels–Alder Reaction of α‑Pyrones with 5‑<i>H</i>‑1,2,3-Thiadiazoles
The
efficient synthesis of Îł-thiapyrones by a base-mediated
Diels–Alder/retro-Diels–Alder reaction of α-pyrones
with 5-H-1,2,3-thiadiazoles is reported herein. Thioketenes in situ generated from thiadiazoles as electron-poor dienophile
and electron-rich 4-hydroxy-2-pyrones as dienes are conjunctively
transformed into a series of Îł-thiapyrones with broad functional
group compatibility in good to excellent yields (35 examples, 67%
average yield)
Palladium-Catalyzed 1,2-Alkynylarylation of Vinyl Arenes with Haloalkynes and Arylboronic Acids
We
herein disclose a novel palladium-catalyzed 1,2-alkynylarylation
of vinyl arenes using haloalkynes and arylboronic acids as coupling
partners. This reaction is characterized by broad substrate scope,
controllable reaction sequence, and excellent chemo- and regioselectivities.
Mechanistic investigations suggest that the reaction is initiated
by regioselective insertion of vinyl arenes into the alkynyl-Pd(II)
species, and the silver salt is crucial for this transformation, serving
as both the Lewis acid and halide scavenger. This protocol provides
efficient access to new carbon skeletons, which are embedded in the
key biologically active motifs
Base-Mediated Three-Component Tandem Reactions for the Synthesis of Multisubstituted Pyrimidines
A base-mediated
three-component tandem reaction for the synthesis
of multisubstituted pyrimidines from amidines, aryl alkynes, and aldehydes
in a one-pot manner has been developed. Advantages of this transformation
include being transition-metal-free, high efficiency, available starting
materials, and being environmentally friendly
Nucleopalladation Triggering the Oxidative Heck Reaction: A General Strategy to Diverse β‑Indole Ketones
A simple and efficient palladium-catalyzed oxidative coupling between 2-alkynyl anilines and allylic alcohols is described by using cheap and green dioxygen as the oxidant. These cross-couplings have a large functional group tolerance and are of higher reactivity toward electron nonbaised allylic alcohols. The resultant β-indole ketones are readily converted to pharmaceutically significant β-indole alcohol/amine and pyrrolo[2,1-<i>a</i>]isoquinolines
Controllable <i>O</i>‑Nucleometalation Cyclization Strategy: Access to Divergent Ring-Functionalized Molecules
The
vinyl moiety-assisted selective <i>O</i>-nucleopalladation
is reported, which offers rapid constructions of cycloolefins and
cyclopropanes via oxidant-induced cyclization of enynes. O<sub>2</sub> resulted in the unexpected 6-<i>endo</i>-Heck cyclization,
while CuCl<sub>2</sub> led to a 5-<i>exo-trig</i> pathway
and synergetic S<sub>N</sub>2-type C–C bond formation. Amide
works as an <i>O</i>-transferred nucleophilic group to activate
the alkyne moiety, which induced divergent annulation processes. Moreover,
the regenerated amides could be used for further modifications
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