Search results for "alkynyl"

Copper-Catalyzed Aerobic Oxidative Alkynylation of 3,4-Dihydroquinoxalin-2-ones

2019

Herein, we described a ligand-free copper-catalyzed aerobic oxidative functionalization of 3,4-dihydroquinoxalin-2(1H)-ones with terminal alkynes using visible-light and oxygen as terminal oxidant to give 3-ethynyl-3,4-dihydroquinoxalin-2(1H)-one, cyclic propargylic amines, in moderate to good yields. Moreover, we demonstrate the versatility of the 3-ethynyl-3,4-dihydroquinoxalin-2(1H)-ones obtained by preparing several 3,4-dihydroquinoxalin-2-one derivatives.

Atomically Precise Alkynyl-Protected Metal Nanoclusters as a Model Catalyst: Observation of Promoting Effect of Surface Ligands on Catalysis by Metal…

2016

Metal nanoclusters whose surface ligands are removable while keeping their metal framework structures intact are an ideal system for investigating the influence of surface ligands on catalysis of metal nanoparticles. We report in this work an intermetallic nanocluster containing 62 metal atoms, Au34Ag28(PhC≡C)34, and its use as a model catalyst to explore the importance of surface ligands in promoting catalysis. As revealed by single-crystal diffraction, the 62 metal atoms in the cluster are arranged as a four-concentric-shell Ag@Au17@Ag27@Au17 structure. All phenylalkynyl (PA) ligands are linearly coordinated to the surface Au atoms with staple "PhC≡C-Au-C≡CPh" motif. Compared with reporte…

Comparative biological evaluation and G-quadruplex interaction studies of two new families of organometallic gold(I) complexes featuring N-heterocycl…

2020

Experimental organometallic gold(I) compounds hold promise for anticancer therapy. This study reports the synthesis of two novel families of gold(I) complexes, including N1-substituted bis-N-heterocyclic carbene (NHC) complexes of general formula [Au(N1-TBM) 2]BF 4 (N1-TBM = N1-substituted 9-methyltheobromin-8-ylidene) and mixed gold(I) NHC-alkynyl complexes, [Au(N1-TBM)alkynyl]. The compounds were fully characterised for their structure and stability in aqueous environment and in the presence of N-acetyl cysteine by nuclear magnetic resonance (NMR) spectroscopy. The structures of bis(1-ethyl-3,7,9-trimethylxanthin-8-ylidene)gold(I), (4-ethynylpyridine)(1,9-dimethyltheobromine-8-ylidene)gol…

Ultra-Low Catalyst Loading as a Concept in Economical and Sustainable Modern Chemistry: The Contribution of Ferrocenylpolyphosphane Ligands

2007

The challenge of sustainability in modern chemistry will be met with new technologies and processes provided significant progress is made in several key research areas, such as the expansion of chemistry from renewable feedstock, the design of environmentally benign chemicals and solvents, the minimization of depletive resources, and the development of high-performance catalysis. In this prospect, ligand chemistry is a pivotal science that links modern-organic,-inorganic, -organometallic, and -coordination chemistry through a vast number of valuable applications, precisely associated to catalysis. We review in this article our recent work on catalysis promoted by original ferrocenyl tetra-,…

Enantioselective Synthesis of 4-Substituted Dihydrocoumarins through a Zinc Bis(hydroxyamide)-Catalyzed Conjugate Addition of Terminal Alkynes

2013

A new enantioselective catalyst for the conjugate addition of terminal alkynes has been developed. Terminal alkynes react with 3-alkoxycarbonylcoumarins in the presence of diethylzinc and bis(hydroxyamide) ligands to give chiral non-racemic dihydrocoumarins substituted with an alkynyl group on the C-4 position with good yields and enantiomeric excesses up to 95%.

A coumarin based gold(i)-alkynyl complex: a new class of supramolecular hydrogelators.

2014

A phosphine-gold(I)-alkynyl-coumarin complex, [Au{7-(prop-2-ine-1-yloxy)-1-benzopyran-2-one}(DAPTA)] (1), was synthesized and the formation of long luminescent fibers in solution was characterized via fluorescence microscopy and dynamic light scattering. The fibers presented strong blue and green luminescence, suggesting that the gold(I) in the complex increased intersystem crossing due to the heavy atom effect, resulting in a significant increase in triplet emission. The X-ray structure of the fibers indicates that both aurophilic, π–π interactions and hydrogen bonding contribute to their formation in aqueous solvents.

Enantioselective alkynylation of benzo[e][1,2,3]-oxathiazine 2,2-dioxides catalysed by (R)-VAPOL-Zn complexes: synthesis of chiral propargylic cyclic…

2015

[EN] (R)-VAPOL-Zn(II) complexes catalysed the enantioselective addition of terminal alkynes to cyclic benzoxathiazine 2,2-dioxides, providing the corresponding chiral propargylic sulfamidates with high yields (up to 93%) and good enantiomeric excesses (up to 87%).

A straightforward copper-free palladium methodology for the selective alkynylation of a wide variety of S-, O-, and N-based mono- and diheterocyclic …

2009

Abstract High-yield alkynylations are successfully achieved by a simple and widely accessible catalytic system for an unprecedented variety of heterocyclic bromides and chlorides in position -2, -3 or -5: pyridine, quinoline, thiophene, furan, thiazole, benzothiazole, pyrimidine, pyridazine, pyrazine, dioxepin halides are efficiently functionalized in short time reactions. This copper-free methodology employs 1 mol % palladium only, with inexpensive PPh3 and amine base. The ionic liquid solvent allows a straigtforward separation of products and recycling opportunity. Unsuitable substrates and secondary reactions are also reported in order to point out further progress in cross-coupling usin…

ChemInform Abstract: Highly Enantioselective Zinc/Binol-Catalyzed Alkynylation of N-Sulfonyl Aldimines.

2008

Catalytic Enantioselective Conjugate Alkynylation of α,β-Unsaturated 1,1,1-Trifluoromethyl Ketones with Terminal Alkynes.

2016

The first catalytic enantioselective conjugate alkynylation of α,β-unsaturated 1,1,1-trifluoromethyl ketones has been carried out. Terminal alkynes and 1,3-diynes were treated with trifluoromethyl ketones in the presence of a low catalytic load of a CuI-MeOBIPHEP complex (2.5 mol %) and triethylamine (10 mol %) to give the corresponding trifluoromethyl ketones bearing a propargylic stereogenic center at the β position with good yields and excellent enantiomeric excesses in most of the cases. No 1,2-addition products were formed under the reaction conditions. The procedure showed broad substrate scope for alkyne, diyne, and enone. A rationale for the observed stereochemistry has been provide…