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

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

Intrinsic time resolution of 3D-trench silicon pixels for charged particle detection

In the last years, high-resolution time tagging has emerged as the tool to tackle the problem of high-track density in the detectors of the next generation of experiments at particle colliders. Time resolutions below 50ps and event average repetition rates of tens of MHz on sensor pixels having a pitch of 50$\mu$m are typical minimum requirements. This poses an important scientific and technological challenge on the development of particle sensors and processing electronics. The TIMESPOT initiative (which stands for TIME and SPace real-time Operating Tracker) aims at the development of a full prototype detection system suitable for the particle trackers of the next-to-come particle physics experiments. This paper describes the results obtained on the first batch of TIMESPOT silicon sensors, based on a novel 3D MEMS (micro electro-mechanical systems) design. Following this approach, the performance of other ongoing silicon sensor developments has been matched and overcome, while using a technology which is known to be robust against radiation degradation. A time resolution of the order of 20ps has been measured at room temperature suggesting also possible improvements after further optimisations of the front-end electronics processing stage.Comment: This version was accepted to be published on JINST on 21/07/202

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

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

Idrogenazioni selettive di substrati polinsaturi

Dottorato di ricerca in scienze chimiche. Relatore L. TonioloConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

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