Search results for "Cycloisomerization"
showing 8 items of 8 documents
Gold(I) Complexes Nuclearity in Constrained Ferrocenyl Diphosphines: Dramatic Effect in Gold‐Catalyzed Enyne Cycloisomerization
2020
International audience; Di-tert-butylated-bis(phosphino)ferrocene ligands bearing phosphino substituents R (R=phenyl, cyclohexyl, isopropyl, mesityl, or furyl) allow tuning the selective formation of Au(I) halide complexes. Thus, dinuclear linear twocoordinate, but also rare mononuclear trigonal three-coordinate and tetrahedral four-coordinate complexes were formed upon tuning of the conditions. Both Au(I) chloride and rarer Au(I) iodide complexes were synthesized, and their X-ray diffraction analysis are reported. The significance of the control of structure and nuclearity in Au(I) complexes is further illustrated herein by its strong effect on the efficiency and selectivity of gold-cataly…
Gold-Catalyzed Intramolecular Hydroamination of o-Alkynylbenzyl Carbamates: A Route to Chiral Fluorinated Isoindoline and Isoquinoline Derivatives
2013
Enantiomerically pure fluorinated isoindoline and dihydroisoquinoline scaffolds have been prepared through a diastereoselective addition of fluorinated nucleophiles to Ellman’s N-(tert-butanesulfinyl)imines followed by a sequence of Sonogashira cross-coupling/gold(I)-catalyzed cycloisomerization of the corresponding carbamate. A more favored 5-exo-dig mechanism was observed mainly due to an electronic effect of the fluorinated group.
Highly Robust but Surface‐Active: An N‐Heterocyclic Carbene‐Stabilized Au 25 Nanocluster
2019
Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters that are surface-active for liquid-phase catalysis without any pre-treatment. Now, an N-heterocyclic carbene-stabilized Au25 nanocluster with high thermal and air stabilities is presented as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25 (i Pr2 -bimy)10 Br7 ]2+ (i Pr2 -bimy=1,3-diisopropylbenzimidazolin-2-ylidene) (1), was synthesized by direct reduction of AuSMe2 Cl and i Pr2 -bimyAuBr with NaBH4 in one pot. X-ray crystallization…
Nanocatalysts for High Selectivity Enyne Cyclization: Oxidative Surface Reorganization of Gold Sub-2-nm Nanoparticle Networks
2021
International audience; Ultrasmall gold nanoparticles (NPs) stabilized in networks by polymantane ligands (diamondoids) were successfully used as precatalysts for highly selective heterogeneous gold-catalyzed dimethyl allyl(propargyl)malonate cyclization to 5-membered conjugated diene. Such reaction usually suffers from selectivity issues with homogeneous catalysts. This control over selectivity further opened the way to one-pot cascade reaction, as illustrated by the 1,6-enyne cycloisomerization–Diels–Alder reaction of dimethyl allyl propargyl malonate with maleic anhydride. The ability to assemble nanoparticles with controllable sizes and shapes within networks concerns research in sensor…
Highly Robust but Surface-Active: N-Heterocyclic Carbene-Stabilized Au25 Nanocluster as a Homogeneous Catalyst
2019
<div> <div> <div> <p>Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters that are surface-active for liquid-phase catalysis without any pre-treatment. Herein, we report a novel N-heterocyclic carbine-stabilized Au25 nanocluster with high thermal and air stabilities as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25(iPr2-bimy)10Br7]2+ (iPr2-bimy=diisopropyl-benzilidazolium) (1), was synthesized by direct reduction of AuSMe2Cl and iPr2- bimyAuBr with NaBH4 in o…
Silica-Immobilized NHC-Gold(I) Complexes: Versatile Catalysts for the Functionalization of Alkynes under Batch and Continuous Flow Conditions
2017
Immobilized sterically demanding NHC-Au(I) complexes silica-[(IPrR)Au]Cl and silica-[(IAdPrR)Au]Cl are synthesized and characterized. These complexes are suitable catalysts in typical homogeneous Au(I)-catalyzed alkyne reactions such as hydration, hydroamination, hydroarylation, or cycloisomerization. The results obtained with the immobilized catalysts in reactions in batch are comparable to those obtained with their homogeneous counterparts with the advantage of easily recovered and recycled in successive reactions. Their catalytic activity decreases when reused in batch reactions, probably because of crushing that is associated with magnetic stirring. In contrast, these immobilized cataly…
ChemInform Abstract: Gold-Catalyzed Intramolecular Hydroamination of o-Alkynylbenzyl Carbamates: A Route to Chiral Fluorinated Isoindoline and Isoqui…
2013
Title compounds are prepared in enantiomerically pure form by the diastereoselective addition of fluorinated nucleophiles to N-(tert-butanesulfinyl)imines (I) followed by a sequence of Sonogashira cross-coupling/gold(I)-catalyzed cycloisomerization of the corresponding carbamate.
Thiol-Stabilized Atomically Precise, Superatomic Silver Nanoparticles for Catalyzing Cycloisomerization of Alkynyl Amines
2018
Abstract Both the electronic and surface structures of metal nanomaterials play critical roles in determining their chemical properties. However, the non-molecular nature of conventional nanoparticles makes it extremely challenging to understand the molecular mechanism behind many of their unique electronic and surface properties. In this work, we report the synthesis, molecular and electronic structures of an atomically precise nanoparticle, [Ag206L72]q (L = thiolate, halide; q = charge). With a four-shell Ag7@Ag32@Ag77@Ag90 Ino-decahedral structure having a nearly perfect D5h symmetry, the metal core of the nanoparticle is co-stabilized by 68 thiolate and 4 halide ligands. Both electroche…