Fast and Efficient Nitration of Salicylic Acid and Some Other Aromatic Compounds over H_3PO_4/TiO_2-ZrO_2 Using Nitric Acid

TiO₂‐ZrO₂ (1/1)‐surf with Ti and Zr molar ratio of 1/1 was prepared with surfactant through a sol‐gel method. The optimum experimental condition was investigated for nitration of salicylic acid. Then, a number of nitration reactions were carried out with a variety of aromatic compounds in the optimum condition. The 25 wt% H₃PO₄/TiO₂‐ZrO₂ (1/1)‐surf catalyst showed good selectivity and yield in a short time for the nitration of salicylic acid and some other aromatic compounds.     

An Efficient Method for the Synthesis of N-Acylsulfonamides: One-pot Sulfonylation and Acylation of Primary Arylamines under Solvent-Free Conditions

Summary. The preparation of N-acylsulfonamides is described using primary amines, arylsulfonyl chlorides and acyl chlorides. Reaction of primary aryl amines with arylsulfonyl chlorides in the presence of NaHCO₃ produced N-arylsulfonamides, which reacted in situ with benzoyl chloride furnishing the corresponding N-benzoyl-N-arylsulfonamides in 72–96% yields. Accordingly, 4-nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were used as acylating agents. All the reactions were carried out under solvent-free conditions at room temperature and the products were isolated after simple work-up in high yields and purity.     

P2O5/SiO2 as an efficient and recyclable catalyst for N-Acylation of sulfonamides under heterogeneous and solvent-free conditions

A convenient synthetic method for N-acylation of sulfonamides in the presence of P₂O₅/SiO₂ is described. Carboxylic acid anhydrides and carboxylic acid chlorides were used as acylating agents and the reactions were carried out in CH₂Cl₂ or solventfree conditions. The catalyst can be recovered by simple filtration and can be used in the subsequent reactions.     

In situ trapping of Boc-2-pyrrolidinylmethylzinc iodide with aryl iodides: direct synthesis of 2-benzylpyrrolidines

Addition of (S)-(+)-tert-butyl 2-(iodomethyl)pyrrolidine-1-carboxylate to activated zinc, aryl halides, and a catalyst derived from Pd(2)(dba)(3) (2.5 mol %) and SPhos (5 mol %) in DMF allows trapping of the corresponding organozinc reagent, with formation of Boc-protected 2-benzylpyrrolidines (20-72%).     

A novel and efficient solvent-free and heterogeneous method for the synthesis of primary, secondary and bis-N-acylsulfonamides using metal hydrogen sulfate catalysts

Some metal hydrogen sulfates were used as acid catalysts in the N-acylation of different sulfonamides using carboxylic acid chlorides and anhydrides as acylating agents under both heterogeneous and solvent-free conditions. Al(HSO₄)₃ and Zr(HSO₄)₄ were found to have the highest activity and catalyze the reactions efficiently to furnish the primary N-acyl sulfonamides (RCONHSO₂R′), secondary N-acylsulfonamides (RCONR″SO₂R′) and bis-N-acylsulfonamnides [RCO(SO₂R′)N-R″-N(SO₂R′)COR] in good to high yield. The mild reaction conditions, inexpensive and low toxicity of catalysts and easy work-up procedure make this method attractive.     

Highly Selective Vapor-Phase Acylation of Veratrole over H_3PO_4/TiO_2-ZrO_2: Using Ethyl Acetate as a Green and Efficient Acylating Agent

A simple sol‐gel method with and without surfactant was applied to prepare TiO₂‐ZrO₂ mixed oxides containing Ti and Zr at a molar ratio of 1:1. Several catalysts containing w=15% –35% H₃PO₄ were set up using these mixed oxides. The physical and chemical properties of catalysts were investigated by BET, SEM and pyridine adsorption‐desorption. The catalytic performance of each material was determined for the vapor‐phase acylation of veratrole (1,2‐dimethoxybenzene) to 3,4‐dimethoxyacetophenone (3,4‐DMAP), which was found to be the major product of the reaction of veratrole with ethyl acetate, with alkylated products being the minor products. 2,3‐Dimethoxyacetophenone (2,3‐DMAP) was not detected in the product stream. In the best experimental conditions, the alkylated products were less than 0.7%. This reaction may represent an environmentally friendly alternative to use the ethyl acetate as the acylating reagent. The feed molar ratios of veratrole/ethyl acetate were varied over a wide range of 0.1 to 1, and the optimum feed ratio of veratrole/ethyl acetate was 1:3. Space velocity employed in the veratrole acylation reported as WHSV (veratrole) was 1.2 h^?1. The acylation reactions were carried out in the temperature range of 423 to 673 K and the optimum H₃PO₄ content for acylation was w=15%.     

Gas-phase study of new organozinc reagents by IRMPD-spectroscopy, computational modelling and tandem-MS

An extensive set of organozinc iodides, useful for Negishi-type cross-coupling reactions, are investigated as respective cations after formal loss of iodide in the gas phase. Firstly, two new alkylzinc compounds derived from Tyrosine (Tyr) and Tryptophan (Trp) are closely examined. Secondly, the influence of specific protecting groups on the subtle balance between intra- and intermolecular coordination of zinc in these reagents is probed through trifluoroacetyl (TFA)-derivatized alkylzinc compounds. Finally, the influence of the strongly coordinating bidentate ligand N,N,N',N'-tetramethylethylenediamine (TMEDA) on the structure of alkylzinc cations is further explored in order to better understand the stability of the respective complexes towards water. A combination of electrospray (ESI)-MS/MS, accurate ion mass measurements, infrared multiple-photon dissociation (IRMPD) spectroscopy and computational modelling allowed the full characterisation of all dimethylformamide (DMF)-solvated and TMEDA-coordinated alkylzinc cations in the gas phase. The calculations indicate that the zinc cation in gas-phase alkylzinc-DMF or TMEDA-complex ions preferentially adopts a tetrahedral coordination sphere with four ligands. Additionally, conformers with only three binding partners bound to zinc but with effectively combined hydrogen-bond interactions are also found. Collision induced dissociation (CID) patterns demonstrate that the zinc-DMF interaction in tetrahedral four-coordinate mono-DMF-zinc complex ions as well as the interaction between TMEDA and zinc in the corresponding complex ions is even stronger than typical covalent bonds. In most cases, all major features of the IRMPD spectra are consistent with only a single major isomer, allowing secured identification and assignment.     

Study of acoustic bubble cluster dynamics using a lattice Boltzmann model

The search for the development of a reliable mathematical model for understanding bubble dynamics behavior is an ongoing endeavor.A long list of complex phenomena underlies the physics of this problem.In the past decades,the lattice Boltzmann method has emerged as a promising tool to address such complexities.In this regard,we have applied a 121-velocity multiphase lattice Boltzmann model to an asymmetric cluster of bubbles in an acoustic field.A problem as a benchmark is studied to check the consistency and applicability of the model.The problem of interest is to study the deformation and coalescence phenomena in bubble cluster dynamics,as well as the screening effect on an acoustic multibubble medium.It has been observed that the LB model is able to simulate the combination of the three aforementioned phenomena for a bubble cluster as a whole and for every individual bubble in the cluster.     

Chemoselective and scalable preparation of alkyl tosylates under solvent-free conditions

The improved method for the efficient tosylation of alcohols has been reported using two procedures (A and B). Procedure A: methanol, ethanol, benzyl alcohols, and valuable ethylene glycols can be converted into their corresponding alkyl tosylates in very fast, simple, and efficient grinding method using potassium carbonate as solid base. Other primary and secondary alcohols need to add potassium hydroxide to reaction mixture (procedure B). High selectivity of tosylation was observed for these two procedures. Scale up ability was found in this method even in 100 mmol of substrate. The present method is the example of solid-state tosylation using tosyl chloride, and is a green chemical process due to solvent-free conditions.