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The design and operation of a new kind of high pressure/high temperature stirred IR cell is described. The cell is a stand-alone autoclave made of Hastelloy and effective stirring and gas diffusion are provided by a magnetically driven Teflon shaft. The length of the optical path can be regulated without the need of calibrated spacers and the problem of the sealing of the windows to the cell body has been solved by employing FEP (fluorinated ethylene propylene) encapsulated Viton O- rings, which, upon adapting to the cell when warmed, provide an excellent seal that is also tolerant of all standard solvents. The use of this kind of O-rings allows taking advantage of the chemical resistance of Teflon without needing to mechanically stress the fragile windows as it would be required if bulk Teflon O-rings were employed.

The reductive cyclization of suitably substituted organic nitro compounds by carbon monoxide is a very appealing technique for the synthesis of heterocycles because of its atom efficiency and easiness of separation of the only stoichiometric byproduct CO2, but the need for pressurized CO has hampered its diffusion. We have recently reported on the synthesis of indoles by reductive cyclization of o-nitrostyrenes using phenyl formate as a CO surrogate, using a palladium/1,10-phenanthroline complex as catalyst. However, depending on the desired substituents on the structure, the use of β-nitrostyrenes as alternative reagents may be advantageous. We report here the results of our study on the possibility to use phenyl formate as a CO surrogate in the synthesis of indoles by reductive cyclization of β-nitrostyrenes, using PdCl2(CH3CN)2 + phenanthroline as the catalyst. It turned out that good results can be obtained when the starting nitrostyrene bears an aryl substituent in the alpha position. However, when no such substituent is present, only fair yield of indole can be obtained because the base required to decompose the formate also catalyzes an oligo-polymerization of the starting styrene. The reaction can be performed in a single glass pressure tube, a cheap and easily available piece of equipment.

On the occasion of this Special Issue, I would like to present an editorial message on this good occasion [...]

The reductive cyclization of different organic nitro compounds by carbon monoxide, catalyzed by transition metal complexes, is a very efficient and clean strategy for the synthesis of many N-heterocycles. However, its use requires the use of autoclaves and pressurized CO lines. In this perspective, the authors will present the results obtained in their laboratories on the use of phenyl formate as a convenient CO surrogate, able to liberate carbon monoxide under the reaction conditions and allowing the use of a cheap glass pressure tube as a reaction vessel. In most cases, yields were better than those previously reported by the use of pressurized CO, proving that the use of CO surrogates can be a viable alternative to the gaseous reagent.

The first examples of heterogeneous Fe-catalysed cyclopropanation reactions are presented. Pyrolysis of in situ-generated iron/phenanthroline complexes in the presence of a carbonaceous material leads to specific supported nanosized iron particles, which are effective catalysts for carbene transfer reactions. Using olefins as substrates, cyclopropanes are obtained in high yields and moderate diastereoselectivities. The developed protocol is scalable and the activity of the recycled catalyst after deactivation can be effectively restored using an oxidative reactivation protocol under mild conditions.

In a recent paper on this Journal (J. Catal. 369 (2019) 257–266), we reported on the effect of ppm amounts of iron compounds on the palladium/iodide (and even palladium/chloride) catalytic system for the oxidative carbonylation of aniline to diphenylurea. In a “Polemic” against our work, Gabriele and coworkers argued against some of the conclusions we had drawn and even against our experimental practice. Here, we reply in detail to this polemic. Some of the content of the latter is due to some misunderstanding, whereas some assertions are untenable and in contrast with experimental data.

The palladium/iodide couple is the most investigated catalytic system for the oxidative carbonylation of amines to give ureas or carbamates. In reinvestigating it, we found that the most prominent role of iodide is to etch the stainless steel of the autoclave employed in most of previous works, releasing in solution small amounts of iron salts. The latter are much better promoters than iodide itself. Iron and iodide have a complex interplay and, depending on relative ratios, can even deactivate each other. The presence of a halide is beneficial, but chloride is better than iodide in this respect. The ideal Fe/Pd ratio is around 10, but even an equimolar amount of iron with respect to palladium (0.02 mol% with respect to aniline, corresponding to 12 ppm Fe with respect to the whole solution) is sufficient to boost the activity of the catalytic system. Such small amount may also come from Fe(CO)5 impurities present in the CO gas when stored in steel tanks. The role of the solvent has also been investigated. It was found that the reason for the better selectivity in some cases is at least in part due to a hydrolysis of the solvent itself, which removes the coproduced water.

A series of alkyl and aryl formate esters were evaluated as CO sources in the Pd- and Pd/Ru-catalyzed reductive cyclization of substituted nitro compounds to afford heterocycles, especially indoles. Phenyl formate was found to be the most effective, allowing to obtain the desired products in excellent yields, often higher than those previously reported with pressurized CO. Detailed experiments and kinetic studies discern between a metal-catalyzed and a base-mediated activation of phenyl formate confirming that just the base is effective in catalyzing its decarbonylation.

Reactions of various substituted bis(imino)acenaphthenes (R-BIAN) with FeCl2(thf)1.5 afforded the tetrahedral complexes (R BIAN)FeCl2 (2) from bulky α-diimines and the octahedral complexes [Fe(R-BIAN)3][FeCl4]2 (3) from less bulky ligands. The driving force of the formation of complexes 3 is the high ligand-field stabilization of the low-spin Fe(II). The two sets of complexes exhibit distinct CT band intensities and redox activities. (R BIAN)FeCl2 complexes showed reversible ligand-centered reductions at -0.9 V (vs. FcH/FcH+); further reduction led to decomposition. Irreversible oxidations were observed at 0.2 and 0.4 V associated with a reduction at -0.4 V as well as a ligand-centered redox event at 1.0 V. First applications of the Fe(BIAN) complexes to hydrogenations of alkenes documented good catalytic activity under mild conditions.

Ar-BIANs and related α-diimine Co complexes were wet impregnated onto Vulcan® XC 72 R carbon black powder and used as precursors for the synthesis of heterogeneous supported nanoscale catalysts by pyrolysis under argon at 800 °C. The catalytic materials feature a core-shell structure composed of metallic Co and Co oxides decorated with nitrogen-doped graphitic layers (NGr). These catalysts display high activity in the liquid phase hydrogenation of aromatic nitro compounds (110 °C, 50 bar H 2 ) to give chemoselectively substituted aryl amines. The catalytic activity is closely related to the amount and type of nitrogen atoms in the final catalytic material, which suggests a heterolytic activation of dihydrogen.

In the presence of carbon monoxide, the palladium/phenanthroline system catalyzes the intramolecular amination of thiophene rings following the reduction of a nitroalkene moiety directly attached to the S-heterocyclic ring. Optimization of the ligand and reaction conditions allowed the synthesis of a series of thienopyrroles aryl/alkyl-substituted at either the 2- or 3-position of the pyrrole ring. By using low pressures of carbon monoxide (5 bars), high yields of fused bicyclic compounds have been obtained (up to 98 % yield).

Use of homogeneous catalysts poses the problem of their recovery at the end of the reaction. A possible strategy to circumvent this problem is to make the ligand part of a polymer with limited solubility. In this work, we investigated the immobilization of complexes of Ar-BIAN ligands (Ar-BIAN = bis(arylimido)acenaphthene). We employed 4,4′-methylene-bis(aniline) as an amine able to bridge two acenaphthene moieties. However, the obtained product was a mixture of short-chain oligomers. A ruthenium complex of this mixture (Oligo-BIAN) was indeed catalytically active in the model hydrogenation of nitrobenzene to aniline by CO/H2O but the complexes were too soluble in the reaction mixture to allow for an easy recovery. We thus further extended the molecular weight of Oligo-BIAN by polymerizing it with terephthaloyl chloride obtaining a polyamide (Poly-BIAN). The latter was insoluble in all solvents but its ruthenium complex was catalytically inactive in the model reaction. An deeper investigation, showed that coordination mode of monomeric Ar-BIAN ligands and Oligo-BIAN to [Ru(CO)3Cl2(THF)] is differs from that of Poly-BIAN. This result was completely unexpected and constitutes a general warning not to give for granted the coordination mode of a complex to a functionalized polymer.

Novel unsaturated C10 diesters are produced via the alkoxycarbonylation of δ-lactone 1 (3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one), derived from the telomerization of CO2 and butadiene. The key for the selective valorization of 1 is the use of a catalytic system based on PdCl2, a chelating phosphine bearing electron-withdrawing groups and an acidic promoter. The unsaturated C10 methyl diester can be easily hydrogenated on Pd/C under mild conditions to afford its corresponding saturated diester. Subsequent hydrogenation using the homogeneous [Ru(acac)3]/Triphos catalysts gives 2-ethyloctane-1,8-diol in high yield. The overall procedure allows synthesizing new building blocks for the manufacturing of renewable polymers and polymer processing materials.

1,10-Phenanthrolines are widely employed as ligands, but their use on a large scale is constrained by their difficult purification, which usually requires lengthy chromatographic separations. Herein, we describe a purification strategy that takes advantage of the high stability and low solubility of phenanthroline complexes to separate them from the by products of their synthesis. The formation of ZnCl2 complexes was employed, from which the free ligand can be recovered by reaction with aqueous NH3 in a biphasic CH2Cl2/H2O system. The same strategy was also successfully employed to purify related quinolino-guanidine ligands, demonstrating that the procedure is of general applicability.

An improved hydrogenation of nitroarenes using nano-structured iron- and cobalt-based catalysts is presented. Modifications of the heterogeneous catalysts by N-doped graphene-flakes are crucial for the success of selective reductions. The use of polar solvents and basic additives has a significant positive influence on the rate of reduction of nitroarenes. This allows performing non-noble metal-catalysed hydrogenations under very mild reaction conditions (e.g. 70 °C and 20 bar). On the basis of the obtained catalytic results a heterolytic mechanism for the hydrogenation process is postulated, too.

The novel class of bis-arylaminoacenaphthylenes (Ar-BIANH2) was employed for the preparation of zirconium and yttrium complexes to be used as catalysts for cyclohydroamination of a number of primary and secondary aminoalkenes. The complex [(2,6-iPr2C6H3-BIAN)Zr(NMe2)2(Z1-NHMe2)] was isolated and completely characterized, including X-ray diffraction analysis. Despite its easy and almost quantitative isolation, it showed only moderate catalytic performance in the intramolecular hydroamination, irrespective of the cyclization precursor used. On the other hand, in situ generated YIII complexes obtained using the same class of ligands were found to be very active, leading to the hydroamination of substrates including those normally reluctant in undergoing cyclization such as those featuring an internal non-activated CQC double bond. Electron donating substituents and especially steric hindrance on the ligand improve the performance of the catalysts, allowing us to decrease the catalyst loading to 1 mol% in the latter case.

An efficient catalytic cyclization of β-nitrostyrenes to indoles was developed. The reaction was applied to the synthesis of 3-arylindoles and 2-alkylindoles. Given that in the latter case the starting β-nitrostyrenes can be easily obtained by a Henry reaction, the present method allows indoles to be obtained in a two-step sequence starting from cheap reactants.

Il Co.G.I.C.O. 2018 si è tenuto a Firenze tra il 18 e il 20 luglio 2018 e ha costituito un'occasione importante di confronto tra chimici organici e inorganici sulle tematiche di interesse comune. Quest'anno il congresso, pur mantenendo la sua indipendenza formale, è stato organizzato come sessione parallela di un convegno internazionale a partecipazione molto più elevata, la 28th International Conference on Organometallic Chemistry (ICOMC 2018), cosa che ha permesso a chi ha partecipato di esporre il proprio lavoro ad una platea molto più ampia.

In an effort to understand the first stages of the reduction of nitroarenes to anilines by palladium/phenanthroline complexes and suspecting that arylhydroxylaminato complexes may be intermediates in this process, we investigated the reactivity of [Pd(Neoc)(NO3)2] (Neoc = neocuproine = 2,9-dimethyl-1,10-phenanthroline) with 3,5-dichlorophenylhydroxylamine. Spectroscopic evidence indicates that the desired [Pd(Neoc)(ONHC6H3Cl2)(NO3)] is indeed formed, but the complex is not stable and decomposes within a few hours. Two of the decomposition products were characterized by single crystal X-ray diffraction. They are a N-aryl-N-nitrosohydroxylaminato complex, [Pd(Neoc)(ON(3,5-C6H3Cl2)NO)][NO3] (major decomposition product) and a nitro-nitrate complex [Pd(Neoc)(NO2)(NO3)]. The results indicate that the nitrate ion is not innocent in the starting complex and oxidize hydroxylamine, being reduced itself to NO2− and NO.

A new neutral chiral nitrogen ligand was obtained in one step from commercially available acenaphthenequinone and (R)-(+)-bornylamine. Use of titanium tetraisopropoxide is the key to obtain good yields of the condensed product. Ring strain in the bicyclic system helps in stabilizing the otherwise unstable Alkyl-BIAN type derivative, but is not enough to render the free ligand indefinitely stable. However, complexes of the ligand with the ZnCl2 and NiBr2 fragment were prepared and are stable. The single crystal X-ray structure of ((R)-(+)-Bornyl-BIAN)NiBr2 has been determined.

The accurate electron density distribution in Pd(Neoc)Cl2 (CO) (Neoc = 2,9-dimethyl-1,10-phenanthroline) was measured and calculated to investigate the chemical bonding features, the electrostatic forces and the polarizable bonds in this complex, which is a prototype of the proposed intermediate in the catalytic carbonylation of amines and nitroarenes. The quantum theory of atoms in molecules enables to investigate the nature of the elusive fifth coordination in the complex, which is approximately intermediate between a bypiramid penta-coordination and a square planar tetra-coordination. The analysis of the electrostatic potential and of the distributed atomic polarizabilities enables to address the sites that are more prompt to react, in particular in the context of the catalytic cycle. © 2017 Wiley Periodicals, Inc.

An unprecedented reactivity of aryl azides toward alkynes is presented herein. The reaction performed well in the presence of 2 mol % of ruthenium porphyrin catalysts and afforded substituted indoles instead of triazoles. The procedure is particularly appealing for the synthesis of C3-functionalized indoles which bear EWG on the fragment coming from the azide. The method allowed the synthesis of 15 derivatives with yields up to 95%, high regioselectivity, and without requiring the time-consuming prefunctionalization of reagents and the addition of oxidants and/or additives.

The article describes the organizational model of the social and health services chosen by Marche Region both at regional and local level. At regional level the planning function prevails, while locally the prevailing function is based on management. The article also gives an analysis of the implementation state of the social-health integration’s regional system.

A new nonsymmetric bis(aryl-imino)acenaphthene (Ar-BIAN) ligand, featured by a subtle steric and electronic unbalance of the N-donor atoms, is reported. With the new ligand and the corresponding symmetrically substituted derivatives, both neutral and monocationic PdCH3 compounds have been synthesized and characterized. The series of the monocationic complexes [Pd(CH3)(L)(Ar-BIAN)][PF6] (L=CH3CN, dmso) has been extended to dimethyl sulfoxide derivatives. The monocationic complexes are tested as precatalysts for the ethylene/methyl acrylate cooligomerization under mild reaction conditions of temperature and ethylene pressure. The catalytic product is a mixture of ethylene/acrylate cooligomers and higher alkenes. The catalysts containing the new nonsymmetric ligand are found to be more productive than those with the symmetric Ar-BIANs. The Pd–dmso catalysts are more productive and show a longer lifetime than their Pd–NCCH3 counterparts.

New copper complexes of several thiosemicarbazones have been prepared and characterized. All complexes have been prepared by employing Cu (II) acetate hydrate, but analytical and spectroscopical data for the isolated complexes revealed that in most cases a reduction to copper (I) occurred. Cyclopropanation reactions of several olefins by ethyldiazoacetate (EDA) in the presence of catalytic amounts of the complexes were examined. The reported results showed that all complexes are competent catalysts for the cyclopropanation reaction of unactivated olefins. Cyclopropanes were obtained in high yields (up to 97%, TON up to 18,400) with moderate to excellent diastereoselectivities (up to >99%).

Shedding light on azides: [Ru(TPP)CO] (TPP=tetraphenyl porphyrin dianion), white light and O(2) were found to be a suitable catalyst combination to perform the annulation of several biaryl azides. The high chemoselectivity of the process allows the synthesis of phenanthridines and dihydrophenanthridines in good yield and purity.

This paper describes the synthesis of allylic amines by aryl azides (ArN3) catalysed by [Ru(TPP)CO] (TPP = dianion of tetraphenylporphyrin). The employment of aryl azides renders the methodology sustainable as the formation of molecular nitrogen is the only stoichiometric byproduct. The isolation of catalytic intermediates and spectroscopic and kinetic studies revealed interesting information about the reaction mechanism, which could improve its catalytic efficiency in future research. An important result is the X-ray characterisation of [Ru(TPP)(ArN)2] [Ar = 3,5-(CF3)2C6H3], which is active in both stoichiometric and catalytic nitrene transfer reactions. The proposed involvement of carbonyl-monoimido-ruthenium porphyrin complexes in the catalytic cycle is also derived from our kinetic and experimental results. All the data indicate the coexistence of two mechanisms, where the electronic nature of the engaged aryl azide and olefin concentration determine one mechanism or the other.

The synthesis and characterization of copper(I) complexes of the novel pyridine-containing macrocyclic ligand (PC-L) and their use as catalysts in the Henry reaction are reported. The pyridine-based 12-membered tetraaza macrocyclic (PC-L) ligand 1 can be obtained in good overall yield (85%) from commercially available starting materials. The Cu(I) complexes showed good catalytic activities in the Henry reaction of different aldehydes and nitroalkanes. Remarkable diastereoselectivity was observed when isatine was reacted with nitroethane under catalytic conditions. Copyright © 2011 John Wiley & Sons, Ltd.

A review of synthetic methodologies reported in the last five years that yield N-heterocyclic products by intramolecular cyclization of organic azides with a particular emphasis on transformations catalyzed by metal complexes is presented. These reactions have been classified according to the ring size of the formed heterocycle.

We report herein the synthesis of the porphyrins 5,10,15,20-tetrakis(4-carboxybiphenyl)-porphyrin (H2TCBP) and 5,10,15,20-tetrakis(4-carboxy-2,6-dimethylbiphenyl)porphyrin (H2TCDMBP) bearing diphenyl units on meso-positions, and of their cobalt and silver derivatives. The silver complexes of H2TCDMBP and of H2TCPP ( H2TCPP = 5 ,10,15,20-tetrakis(4-carboxyphenyl)porphyrin) were investigated by X-ray crystallography and their supramolecular organization elucidated. Co(TCBP) was reacted with copper formate, yielding a polymeric compound that showed a catalytic activity in the benzylic amination of hydrocarbons using arylazide as aminating agent.

Benzylic amines are synthesized in yield up to 90% by the Ru(TPP)CO -catalyzed amination of both exocyclic and endocyclic benzylic C-H bonds. The choice of arylazides as nitrogen sources confers to the methodology a good sustainability due to the formation of molecular nitrogen as the only stoichiometric by-product. A preliminary mechanistic investigation evidenced a critical role of the hydrocarbon concentration to drive the chemoselectivity of the reaction.

Polymeric membranes embedding a metal complex have been previously employed as reusable catalysts under relatively mild conditions. Herein, the first example of a polymeric catalytic membrane employed under very forcing conditions (160 °C and 5 MPa CO) is reported. The reaction investigated was the reduction of nitrobenzene to aniline by CO/H 2 O, catalyzed by ruthenium bis(arylimino)acenaphthene (Ar-BIAN) complexes. To better retain the complex in the membrane, a modified ligand, with long alkyl chains in the para positions of the aryl rings, was prepared. Among several polymers tested as membranes, PEEK-WC, a modified polyether ether ketone, gave the best results. Attempts to embed the ligand only in the membrane and functionalize it with the metal later, analogously to the in situ generation of the active species practiced for the homogeneous system, failed and it was necessary to synthesize new complexes that could be reduced under the reaction conditions. Best results were obtained using [Ru(Ar-BIAN)(CO) 2 Cl 2 ] + Et 3 N. During the reaction, the complex is transformed into a mixture of [Ru 3 (CO) 12 ] and a reduced form of the ligand, Ar-BIANH 2 . The latter was independently prepared and shown to be able to reduce nitrobenzene even in the absence of any metal. A new kind of support was designed to allow the placing of the membrane in a stirred autoclave. Using only water as solvent, no metal or ligand leaching was detected and several recycles were performed. All employed membranes were thoroughly characterized by different techniques.

Inspired by the results of a previous mechanistic study, a series of mostly new nonsymmetric phenanthrolines were synthesized and tested as ligands in the palladium-catalyzed reductive carbonylation reaction of nitrobenzene to methyl phenylcarbamate. Very good results were obtained when the asymmetry was of an electronic nature (a donating substituent in the para position of one of the two pyridinic rings and an electron-withdrawing or no substituent on the para position of the other pyridinic ring), but steric hindrance in the ortho or meta position retarded the reaction. The TOF for the modified system is the highest ever reported for any carbonylation reaction of nitroarenes.

In this paper we report the preparation of catalytic polymeric membranes having the complex [( N,N ′- bis (3- tert -butyl-5-(heptadecafluorooctyl)salicylidene)- trans -1,2-cyclohexanediamine)Co] embedded into Hyflon AD60X, PES and PSf and their use in the cyclopropanation reaction of olefins with ethyl diazoacetate (EDA). A study of the reaction in the homogeneous phase was also performed. The kinetics of the cyclopropanation reaction is first-order in the diazoacetate and the catalyst and zero order in the olefin, but we observed a more complex dependence on the additive, NMI ( N -methylimidazole). The positive effect of the additive is completely reversed at NMI concentration higher than 6·10 −2 M.

The addition of Ru3(CO)12, dimethyl carbonate, or both to the reaction mixture improves the selectivity of the palladium/phenanthroline-catalyzed reaction of nitroarenes, arylalkynes, and CO to give 3-arylindoles. When 4-fluorophenylacetylene and nitrobenzene are used as substrates, the indole skeleton of Fluvastatin and other pharmaceutically active compounds is obtained in one step.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)