One-pot oximation–Beckmann rearrangement of ketones and aldehydes to amides of industrial interest: Acetanilide, caprolactam and acetaminophen

High yielding one-pot oximation–Beckmann rearrangement of ketones to amides in ktrifluoroacetic acid has been conducted on several ketones and aldehydes. The substrate reactivity showed to depend on both oximation and Beckmann rearrangement reaction rate. In this synthetic procedure, trifluoroacetic acid acts as solvent, acid catalyst and organocatalyst and can be easily recycled

Experimental investigation of a novel formulation of a cyanoacrylate based adhesive for self-healing concrete technologies

The selection of an appropriate healing agent is critical to the success of vascular and mini-vascular networks. In self-healing concrete technology, commercially available cyanoacrylate (CA) adhesives have been shown to produce good strength recoveries; however, their rapid curing rate and short shelf-life make them unsuitable for site application. The aim of this study was to develop a modified cyanoacrylate (n-CA) with an extended shelf-life suitable for incorporation in a self-healing system. A series of n-CAs were formed from a commercial Ethyl Cyanoacrylate adhesive mixed with acrylic acid (AA) and nitro-anthraquinone (nAq) in varying ratios. When encapsulated within 3D printed mini-vascular networks (MVNs), the n-CAs remained dormant in liquid form for up to 5 days. The contact angle between the n-CAs and the cement mortar substrate, as measured via the sessile drop technique, decreased significantly with increasing AA content. The mechanical properties (bond strength) and the polymerization hardening of the n-CAs were evaluated over a curing period of 7–21 days, via a series of pull-off tests using cement mortar cubes. The 4:1:02 (CA:AA:nAq) n-CA formulation showed a significant increase in bond strength from 14 to 21 days, with a ceiling value of 2.6 MPa, while the 2:1 (CA:AA) n-CA formulation exhibited a good bond strength after 21 days (1 MPa). Nuclear Magnetic Resonance (NMR) conducted on the n-CAs suggested the formation of several new polymeric species, whilst differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) on the pre- and post-printed MVN material confirmed no significant changes in chemistry with no evidence of polymer degradation. Considered together, the experimental results show the potential for different n-CA formulations to act efficiently as a healing agent

Phosgene-free synthesis of 1,3-diphenylurea via catalyzed reductive carbonylation of nitrobenzene

1,3-Diphenylurea (DPU) has been proposed as a synthetic intermediate for phosgene-free synthesis of methyl N-phenylcarbamate and phenyl isocyanate, which are easily obtained from the urea by reaction with methanol. Such an alternative route to synthesis of carbamates and isocyanates necessitates an improved phosgene-free synthesis of the corresponding urea. In this work, it is reported that Pd(II)-diphosphine catalyzed reductive carbonylation of nitrobenzene in acetic acid (AcOH)-methanol proceeds in high yield and selectivity as a one-step synthesis of DPU. We have found that the catalytic activity and selectivity of this process depends on solvent composition and on the bite angle of the diphosphine ligands. Under optimum reaction conditions, yields in excess of 90 molar % and near-quantitative selectivity can be achieved

Sorption and separation of palladium, platinum and gold chlorocomplexes by means of a dipicolinic acid polystyrene-based chelating resin

A chelating ion-exchange resin containing dipicolinic acid as functional group and based on microporous chloromethylated cross-linked polystyrene-divinylbenzene (2 %) copolymer has been prepared. Its sorption and desorption characteristics for Pd(II), Pt(II), Pt(IV) and Au(III) have been studied in aqueous chloride solutions under a number of experimental conditions, both in batch and in column, at room temperature and constant ionic strength (μ = 1 mol/l, KCl/ HCl). In column operations at pH 6, Pd(II) can be separated from Pt(H) or Pt(IV) owing to the different rate of formation of the immobilized chelated species. From a mixture of Pd(II, Pt(IV) and Au(III) at pH 6, Pt(IV) flows unaffected, whereas Au(III) and Pd(II) are both retained and successively separated by selective elution. From the same mixture at pH ≤ 0 only Au(III) is sorbed by anionic exchange. © 1991

Terpolymerisation of 1-olefin and ethene with CO catalysed by the [PdCl2(dppp)] complex in methanol as a solvent [dppp = 1,3-bis(diphenylphosphino)propane]

The catalytic activity of the [PdCl2(dppp)] complex in the 1-olefin/ethene (E)/CO terpolymerisation has been studied in MeOH (containing 1000 ppm of H2O) as a solvent. The 1-olefins tested were propene (P), 1-hexene (Hex), 1-decene (D) and styrene (S). At 90 °C and 45 atm (E/CO = 1/1), the system [PdCl2(dppp)]/TsOH (p-toluenesulfonic acid) = 1/8 catalyses efficiently the reactions leading to 5000 g PECO/(g Pd h), 5600 g HexECO/(g Pd h), 5650 g DECO/(g Pd h) and 4100 g SECO/(g Pd h). In particular, it has been studied deeper the effect of Hex and S concentrations on productivities, average molecular weights and melting temperatures of HexECO and SECO, respectively. A mechanism of reaction has been also proposed and discussed, supported by IR, and NMR characterizations

One-pot oximation–Beckmann rearrangement of ketones and aldehydes to amides of industrial interest: Acetanilide, caprolactam and acetaminophen

High yielding one-pot oximation–Beckmann rearrangement of ketones to amides in ktrifluoroacetic acid has been conducted on several ketones and aldehydes. The substrate reactivity showed to depend on both oximation and Beckmann rearrangement reaction rate. In this synthetic procedure, trifluoroacetic acid acts as solvent, acid catalyst and organocatalyst and can be easily recycled

Synthesis of phenyl isocyanate and derivates via oxidative carbonylation of aniline catalyzed by Pd(II)-based redox systems

One of the challenges in current day catalysis is to replace wasteful and dangerous industrial processes by more environmentally friendly and safer ones. An example of such a challenge is to replace the highly toxic and corrosive phosgene often used as carbonylating agent. An important example, from an industrial point of view, is represented by the synthesis of isocyanates, starting materials for the production of polyurethanes, actually performed by treating amines with phosgene. Among the numerous phosgene-free methods reported in the literature to produce isocyanates, carbamates and ureas, the reductive carbonylation of nitro compounds and the direct oxidative carbonylation of amines represents a valid alternative to the traditional methods. The Pd-catalyzed carbonylation of aniline to phenylisocyanate, phenylcarbamate or 1,3-diphenylurea has been deeply studied and appears particularly attractive from the standpoint of atom economy. In such a systems, the catalyst consists of a Pd(II) salt that, to form the desiderated products, is reduced to inactive Pd(0) species. The reoxidation of such species to Pd(II) active ones is a key step which permits the restarting of the catalytic cycle. As a matter of fact, the direct reoxidation of Pd(0) species by molecular oxygen is so slow that the precipitation of inactive palladium metal (palladium black) often competes with the reoxidation itself, making inefficient the catalysis. Several methods have been proposed and developed to circumvent this problem mainly based on two strategies which can work at the same time: 1) the stabilization of reoxidable Pd(0) complexes, avoiding the formation of Pd metal; 2) the increasing of the Pd(0) reoxidation rate. An interesting proposal widely adopted in literature is to increase the rate of Pd(0) reoxidation step by inserting an electron-transfer mediator (ETM) between the substrate-selective catalyst and O2 or H2O2 as terminal oxidant. This ETM would then carry the electrons from the metal to the oxidant along a low-energy pathway which would compete kinetically with side reactions of the reduced form of the metal (precipitation, decomposition). Actually, the ETM’s (redox cocatalysts) proposed in literature are mainly metal compounds of varying valences. Salts of Cu, Fe, Ag and heteropolyacids like H3PMo12O40 are the most frequently used cocatalysts, which are able to oxidize Pd(0) to Pd(II), allowing to restart the main reaction cycle. In the present work we synthesized directly phenyl isocyanate through the oxidative carbonylation of aniline catalyzed by a Pd(II)-based multistep redox system in which oxygen is used as terminal oxidant

Influence of formic acid and water on the [Pd(OAc)2(dppp)] catalyzed ethene–carbon monoxide copolymerization carried out in aprotic organic solvents

The copolymerization of ethene with carbon monoxide catalyzed by [Pd(OAc)2(dppp)] in an aprotic solvent such as 1,4-dioxane or nitromethane is efficiently promoted both by H2O and HCOOH and yields a perfectly alternating polyketone (PK). The influence of the concentration of the promoters, pressure and temperature on the catalyst productivity and the limiting viscosity number (LVN) has been studied. The productivity increases with the increase of temperature and pressure. The LVN increases upon increasing the pressure and lowering the temperature. At 363 K and 9.0 MPa, in HCOOH/H2O/1-4,dioxane (2.7/1.35/1 molar ratio), the productivity is 37.50 kgPK (gPd h)−1 (LVN 2.77 dL g−1). LVN lowers upon increasing the concentration of the acid, suggesting that it is involved in the protonolysis chain-transfer process

The coupling of carbon dioxide with ethene to produce acrylic acid sodium salt in one pot by using Ni(II) and Pd(II)-phosphine complexes as precatalysts

The use of CO2 as a feedstock for chemical synthesis is considered as a viable alternative option to some traditional processes. One of the most interesting challenge for the industry is represented by the CO2 coupling with olefins to produce acrylate. Only recently, with the choice of suitable ligands and the use of a sacrificial base, a selective catalytic reaction was established by using Ni(0)-based complexes. The one-pot reaction, which leads to the highest TON (107 mol/mol Ni, in 20 h) reported so far, was successfully developed starting from Ni(0)-based precursors in the presence of disphosphine ligands, a large excess of base and of finely powdered zinc. In the present paper, we carried out the catalytic synthesis of sodium acrylate from CO2 and ethene, in one-pot, by using Ni(II)-chloride and Pd(II)-chloride phosphine-complexes as precatalyst. The reaction occurs under basic conditions and without adding any external reductants. The Ni(II) complexes lead to higher TON than the respective Pd(II) precursors and the best results are obtained by using diphosphines having high bite angles. Such catalysis is favored by aprotic and polar solvents in which a TON of 290 mol/mol Ni is reached by using the [NiCl2 (dppp)] precursor in DMSO. Furthermore the TON could be increased by increasing the temperature, the base concentration and by using diphosphine ligands having high bite angle