A Green and Efficient Solvent- and Catalyst-Free Ultrasonic Dibenzylation Procedure

A greener improvement was achieved for the synthesis of diverse N,N-dibenzylated compounds from the reaction of various aromatic amines with benzyl bromide using the ultrasound irradiation in solvent- and catalyst-free conditions. The dibenzylation reactions were carried out in different solvents and solvent-free conditions under ultrasound irradiation at various temperatures. The yields were very low in all applied solvents, while in the solvent-free condition and at room temperature, the yields were excellent. Due to obtaining the high reaction yields, the catalyst was not used.

Reductive Alkylation of Azides and Nitroarenes with Alcohols: A Selective Route to Mono- and Dialkylated Amines

Herein, we demonstrated an efficient protocol for reductive alkylation of azides/nitro compounds via a borrowing hydrogen (BH) method. By following this protocol, selective mono- and dialkylated amines were obtained under mild and solvent-free conditions. A series of control experiments and deuterium-labeling experiments were performed to understand this catalytic process. Mechanistic studies suggested that the Ir(III)-H was the active intermediate in this reaction. KIE study revealed that the breaking of the C-H bond of alcohol might be the rate-limiting step. Notably, this solvent-free strategy disclosed a high TON of around 5600. Based on kinetic studies and control experiments, a metal-ligand cooperative mechanism was proposed.

Reductive Amination Revisited: Reduction of Aldimines with Trichlorosilane Catalyzed by Dimethylformamide─Functional Group Tolerance, Scope, and Limitations

Aldimines, generated in situ from aliphatic, aromatic, and heteroaromatic aldehydes and aliphatic, aromatic, and heteroaromatic primary or secondary amines, can be reduced with trichlorosilane in the presence of dimethylformamide (DMF) as an organocatalyst (≤10 mol %) in toluene or CH₂Cl₂ at room temperature. The reduction tolerates ketone carbonyls, esters, amides, nitriles, sulfones, sulfonamides, NO₂, SF₅, and CF₃ groups, boronic esters, azides, phosphine oxides, C═C and C≡C bonds, and ferrocenyl nucleus, but sulfoxides and N-oxides are reduced. α,β-Unsaturated aldimines undergo 1,2-reduction only, leaving the C═C bond intact. N-Monoalkylation of primary amines is attained with a 1:1 aldehyde to amine ratio, whereas excess of the aldehyde (≥2:1) allows second alkylation, giving rise to tertiary amines. Reductive N-alkylation of α-amino acids proceeds without racemization; the resulting products, containing a C≡C bond or N₃ group, are suitable for click chemistry. This reaction thus offers advantages over the traditional methods (borohydride reduction or catalytic hydrogenation) in terms of efficiency and chemoselectivity. Solubility of some of the reacting partners appears to be the only limitation. The byproducts generated by the workup with aqueous NaHCO₃ (i.e., NaCl and silica) are environmentally benign. As a greener alternative, DMA can be employed as a catalyst instead of DMF.

Tandem transformations and multicomponent reactions utilizing alcohols following dehydrogenation strategy

In this review, the progress of tandem transformation of nitro, nitrile and azide functionalities is summarised to develop new C–C and C–N bonds as well as multi-component reactions using alcohols.

Self-Suspended Nanoparticles for N-Alkylation Reactions: A New Concept for Catalysis

The catalytic activity of snowman-like and core-shell Fe3O4/Au nanoparticles (NPs), obtained through a "wet chemistry" approach which directly restitutes nanocatalysts stable and highly active in the reaction medium, was tested towards N-alkylation reactions. The nanocatalysts were tested for the synthesis of secondary amines. The core-shell NPs, thanks to the surface properties, homogeneous dispersion and intimate connection with reagents in the catalyst medium, exhibited an excellent catalytic activity (e. g. >99 % yield and conversion of aniline in very short time and mild conditions). Owing to the magnetic part, the nanoparticles can be easily separated and reused, showing an almost stable activity after 10 cycles.

Pd@[nBu₄][Br] as a Simple Catalytic System for N-Alkylation Reactions with Alcohols

Palladium nanoparticles, simply and briefly generated in commercial and cheap onium salts using supercritical carbon dioxide, have been found to be an effective catalytic system for additive free N-alkylation reaction using alcohols via cascade oxidation/condensation/reduction steps.

Spiers Memorial Lecture. Heterogeneous catalysis: understanding the fundamentals for catalyst design

Taking the chemoselective hydrogenation of substituted nitroaromatics as a base case, it will be shown that it is possible to design improved and new catalysts by attacking the problem in a multidisciplinary way. By combining molecular modeling with in situ operando spectroscopy, and with micro-kinetic and isotopic studies, it is possible to determine how and where on the catalysts the reactant molecules interact. Then, materials synthesis methods can be applied to prepare catalysts with the desired surface active sites and their selective interaction with the reactants.

Supported bimetallic nano-alloys as highly active catalysts for the one-pot tandem synthesis of imines and secondary amines from nitrobenzene and alcohols

All-in-one: supported nanoalloys as efficient heterogeneous catalysts for the one-pot synthesis of imines and secondary amines directly from nitrobenzene and benzylic alcohols using a hydrogen auto transfer strategy.

Palladium-catalyzed N-arylsulfonamide formation from arylsulfonyl hydrazides and nitroarenes

Various N-arylsulfonamides were prepared from nitroarenes and arylsulfonyl hydrazides via hydrogen transfer methodology.

One-pot synthesis of secondary amines from alcohols and nitroarenes on TiO2 loaded with Pd nanoparticles under UV irradiation

TiO₂ loaded with Pd nanoparticles, when irradiated by UV light in alcohols with nitroarenes, successfully produces the corresponding secondary amines with almost quantitative yield, via tandem photocatalytic and catalytic reactions.

Alumina-entrapped Ag catalyzed nitro compounds coupled with alcohols using borrowing hydrogen methodology

Time-yield plots for the N-alkylation of nitroarenes with benzyl alcohol in the presence of Ag/Al₂O₃. (■) conversion; (⋄) N-phenylbenzylamine 3; (▲) N-benzylideneaniline 4; (□) azobenzene 5; and (+) aniline 6.

Supported gold-catalyzed and ammonia-promoted selective synthesis of quinazolines in aqueous media

A highly efficient and selective synthesis of 2,4-disubstituted quinazolines via a hydrogen-transfer strategy was developed under the catalysis of nano-Au/TiO₂ and the assistance of nitrogen source-promotion.

Chlorine as an indicator in the controllable preparation of active nano-gold catalyst

The controllable preparation of nano-gold catalyst maintains a challenge. Except the parameters have been revealed before, here we'd like to show that controllable preparation of active nano-gold catalyst can be achieved using chlorine as an indicator. By tracing the chlorine concentration in the washing step, a series of Au/Fe₂O₃ catalysts were prepared with co-precipitation method. The applying of these catalysts in CO oxidation and reductive nitrobenzene N-alkylation suggested the active catalysts were prepared from solutions containing ~2 ppm chlorine. The catalytic activity dropped dramatically if the chlorine concentration is >4–6 or ≪1 ppm. Extensive characterizations revealed that the active catalyst was composed by nano-gold on the edge of Fe₂O₃ particle with 8.92 Au-Au coordination numbers. Although the real role of chlorine in the variation of catalyst structure and activity was still ambiguous, the current results should promote the controllable preparation of active nano-Au catalyst.

Nanoporous palladium catalyzed silicon-based one-pot cross-coupling reaction of aryl iodides with organosilanes

One-pot cross-coupling of aryl iodides with organosilanes is realized using dealloyed nanoporous palladium as a sustainable and heterogeneous catalyst.

Half-encapsulated Au nanoparticles by nano iron oxide: promoted performance of the aerobic oxidation of 1-phenylethanol

Au nanoparticles half-encapsulated in nano iron oxide are prepared and loaded on alumina as a support. The donation of electrons from nano iron oxide to Au nanoparticles is detected and both the properties of gold and iron oxide are adjusted by the donation. The properties are different from the bulk iron oxide supported gold catalysts, in which the iron oxide is little influenced by the electronic interaction between the two components. The catalyst shows noticeably promoted activity for the aerobic oxidation of 1-phenylethanol over Au-Al2O3 and Au-bulk FeOx. The enhanced catalytic behavior may result from the cooperative effect between the Au nanoparticles and nano iron oxide.