Search results for "Catalysis"
showing 10 items of 5944 documents
ChemInform Abstract: Catalytic Aerobic Oxidative Decarboxylation of α-Hydroxy Acids. Methyl Mandelate as a Benzoyl Anion Equivalent.
2010
Abstract The monomeric square-planar cobalt(III) complex of bis- N,N ′-disubstituted oxamides catalyses the oxidative decarboxylation of α-hydroxy acids with molecular oxygen/pivalaldehyde with very good yields. This reaction offers an interesting alternative in the use of methyl mandelate as a convenient benzoyl anion equivalent.
ChemInform Abstract: Palladium-Polypyrrole Nanocomposites Pd@PPy for Direct C-H Functionalization of Pyrroles and Imidazoles with Bromoarenes.
2016
Palladium–polypyrrole nanocomposites (Pd@PPy) with unique combination of high palladium dispersion (nanoparticle size 2.4 nm) and high palladium content (35 wt%) are efficient catalysts for the selective arylation of substituted pyrroles and imidazoles with either activated or deactivated aryl bromides. The performances of the recoverable supported palladium catalyst matches the best performances of homogeneous systems based on Pd(OAc)2 at 0.5–0.2 mol%, and largely overwhelm the classical Pd/C catalyst.
New Porphyrin/Fe-Loaded TiO2 Composites as Heterogeneous Photo-Fenton Catalysts for the Efficient Degradation of 4-Nitrophenol
2013
A new class of porphyrin(Pp)/Fe co-loaded TiO2 composites opportunely prepared by impregnation of [5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (H2Pp) or Cu(II)[5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (CuPp) onto Fe-loaded TiO2 particles showed high activities by carrying out the degradation of 4-nitrophenol (4-NP) as probe reaction in aqueous suspension under heterogeneous photo-Fenton-like reactions by using UV-visible light. The combination of porphyrin-Fe-TiO2 in the presence of H2O2 showed to be more efficient than the simple bare TiO2 or Fe-TiO2.
Rearrangements of Nitrile-Stabilized Ammonium Ylides
2014
Rearrangements of nitrile-stabilized ammonium ylides are useful reactions for the construction of alkylamines, nitrogen heterocycles, or carbonyl compounds. In spite of their attractive synthetic potential, they are much less frequently used than rearrangements of ammonium ylides either carrying charge-stabilizing carbonyl groups or being devoid of additional stabilization of the negative charge. This review focuses on different classes of rearrangements of nitrile-stabilized ammonium ylides as well as their application in synthetic organic chemistry. 1 Introduction 2 [1,2]-Stevens Rearrangements 3 [2,3]-Sommelet–Hauser Rearrangement 4 [2,3]-Stevens Rearrangements 5 Competitive [1,2]-, [2,3…
1,5,7-Triazabicyclo[4.4.0]dec-1- ene (TBD), 7-Methyl-TBD (MTBD) and the polymer-supported TBD (P-TBD):Three efficient catalysts for the nitroaldol (H…
2000
Abstract The 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and its 7-methyl derivative (MTBD) have been proven to be of great synthetic utility as catalysts in the nitroaldol (Henry) reaction and for the addition of dialkyl phosphites to a variety of carbonyl compounds. The catalysts were in many cases superior to the parent tetramethylguanidine (TMG). In general the reaction proceeds in a few minutes at 0°C. The polymer-supported-TBD (P-TBD) was also proven to be an efficient promoter of the above cited nucleophilic additions.
ChemInform Abstract: Organocatalytic Enantioselective Aza-Friedel-Crafts Reaction of 2-Naphthols with Benzoxathiazine 2,2-Dioxides.
2015
An organocatalytic enantioselective aza-Friedel–Crafts addition of 2-naphthols to benzoxathiazine 2,2-dioxides is described using a quinine-derived bifunctional catalyst. The method allows the use of a wide range of aromatic compounds as nucleophiles, including 1-naphthol and sesamol, and benzoxathiazines 2,2-dioxides, expanding the existing state of the art enantioselective synthesis of aminomethylnaphthol derivatives.
A New Tandem Cross Metathesis-Intramolecular Aza-Michael Reaction for the Synthesis of α,α-Difluorinated Lactams
2012
A new tandem cross metathesis–intramolecular aza-Michael reaction in which an α,α-difluorinated amide serves as a source of nucleophilic nitrogen is described. This process gives rise to a new family of fluorinated γ- and δ-lactams. The tandem protocol is catalyzed by the Hoveyda–Grubbs second-generation ruthenium catalyst with titanium(IV) tetraisopropoxide as a co-catalyst and it is highly efficient when conjugated ketones are used as the Michael acceptors. With conjugated esters, however, it is necessary to perform a step-by-step procedure in which the cyclization event is activated by the addition of a base. An asymmetric version of the process is also evaluated.
ChemInform Abstract: Cooperative Assistance in Bifunctional Organocatalysis: Enantioselective Mannich Reactions with Aliphatic and Aromatic Imines.
2013
both of which contain a thiourea moiety (Scheme 1).The catalysts are capable of deprotonating suitable nucleo-philes, such as activated carbonyl compounds. This proton-transfer reaction generates an ion pair, which is composed ofthe protonated catalyst and the anionic nucleophile interact-ing through hydrogen bonds. At least one of the NH moietiesin the protonated catalyst is involved in activating theelectrophilic reaction partner.
ChemInform Abstract: Catalytic Enantioselective Friedel-Crafts Reactions of Naphthols and Electron-Rich Phenols
2016
The enantioselective Friedel–Crafts reaction is a powerful tool for the construction of benzylic stereocenters in a stereodefined manner. Significant advances have already been achieved with heteroarenes such as indoles and pyrroles; however, the reaction with homoarenes is less developed. This short review covers the most relevant literature on enantioselective Friedel–Crafts reactions with naphthols and phenols. 1 Introduction 2 Friedel–Crafts Reactions Involving 1,2-Nucleophilic Addition to C=X Bonds 3 Friedel–Crafts Reactions Involving Conjugate Nucleophilic Addition to Electrophilic C=C Bonds 4 Friedel–Crafts Reactions Involving π-Allylic Complexes as Electrophiles 5 ipso-Friedel–Craft…