Search results for "alkynylation"

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.

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%.

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…

Diarylprolinol as a Ligand for Enantioselective Alkynylation of Cyclic Imines

2017

An easily accessible prolinol derived ligand, (S)-bis(3,5-bis(trifluoromethyl)phenyl)(pyrrolidin-2-yl)methanol, has been efficiently applied in the catalytic enantioselective addition of terminal alkynes to cyclic imines using dimethylzinc (Me2Zn) under mild reaction conditions. The developed catalytic system led to chiral propargylic sulfamidates with high yields (up to 97%) and excellent enantioselectivities (up to 97% ee).

Catalytic asymmetric conjugate addition of terminal alkynes to β-trifluoromethyl α,β-enones.

2014

The first enantioselective conjugate alkynylation of β-trifluoromethyl α,β-enones using terminal alkynes and a taniaphos–Cu(I) complex as catalyst is described. Ketones bearing a trifluoromethylated propargylic chiral centre in the β-position were obtained with good yields and high enantiomeric excesses (up to 99%).

Highly enantioselective copper(I)-catalyzed conjugate addition of terminal alkynes to 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones: new ester/amide su…

2013

A highly enantioselective copper-catalyzed conjugate alkynylation of monoactivated enones, namely 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones, is described. The reaction products are obtained with good yields and excellent enantioselectivities (from 92 to 99% ee). The β-alkynylated difluoro(phenylsulfonyl) ketones can be converted into the corresponding β-alkynylated difluoro- and trifluoromethyl ketones, esters and amides. This is the first example on the use of 1,1-difluoro-1-(phenylsulfonyl)-3-en-2-ones as substrates in an enantioselective reaction, which have been shown to be new ester/amide surrogates.