Metal-Catalyzed, Photo-Assisted Selective Transformation of Tertiary Alkylbenzenes and Polystyrenes into Carbonyl Compounds.

Every year, thousands of tons of polystyrene are produced and discarded, filling landfills and polluting the marine environment. Although several degradation alternatives have been proposed, the need for an effective procedure for the chemical recycling of polystyrene still remains. Here, a vanadium-catalyzed reaction, assisted by visible light, promoted the direct, selective conversion of tertiary alkylbenzenes into acetophenone and other ketone derivatives. Likewise, standard polystyrene samples as well as polystyrenes from insulation and packaging waste could be chemically recycled into acetophenone in a scalable way regardless of their molecular weight, polydispersity, or form. Preliminary mechanistic investigations revealed the participation of singlet oxygen, superoxide, and hydroxyl radical species in this homogenously catalyzed process. Acetophenone could be used as an additive to accelerate the reaction and to increase the yields in some cases.

Direct Arylation in the Presence of Palladium Pincer Complexes.

Direct arylation is an atom-economical alternative to more established procedures such as Stille, Suzuki or Negishi arylation reactions. In comparison with other palladium sources and ligands, the use of palladium pincer complexes as catalysts or pre-catalysts for direct arylation has resulted in improved efficiency, higher reaction yields, and advantageous reaction conditions. In addition to a revision of the literature concerning intra- and intermolecular direct arylation reactions performed in the presence of palladium pincer complexes, the role of these remarkably active catalysts will also be discussed.

New Copper, Palladium and Nickel Catalytic Systems: An Evolution towards More Efficient Procedures.

Metal-catalysed reactions are a fundamental tool in synthetic chemistry. Increasingly challenging transformations can be accomplished only by means of certain metal catalysts. However, there still remains the need for a substantial decrease of the amount of catalyst, for better reuse or recycling of such active species, and for the avoidance of relatively toxic solvents in favour of environmentally friendly media. These facts apply to copper-, palladium-, and nickel-catalysed cross-coupling reactions, direct arylations, and oxidative processes. This account summarises our research on the last reactions, featuring an evolution towards more sustainable procedures in this field.

Synthesis, structure, and catalytic applications for ortho- and meta-carboranyl based NBN pincer-Pd complexes.

o- and m-Carborane-based NBN pincer palladium complexes (oCB-L1)Pd, (oCB-L2)Pd, and (mCB-L1)Pd are synthesized in two steps from commercially available starting materials. The pincer complexes were prepared by the reaction of bis-[R(hydroxy)methyl]-1,2-dicarba-closo-dodecaborane (R = 2-pyridyl oCB-L1, 6-methyl-2-pyridyl oCB-L2) or bis-[2-pyridyl (hydroxy)methyl]-1,2-dicarba-meta-dodecaborane (mCB-L1) with [PdCl2(MeCN)2] under mild conditions. The X-ray structure determination of all carboranyl pincer complexes shows unambiguously B-H activation of the carborane cages. The results agree with the Pd-B bonds in all complexes exhibiting strong σ-electron donation. Theoretical calculations reveal the importance of considering the solid state intermolecular hydrogen bonding when investigating the trans influence in organometallic chemistry. A localized orbitals approach has also been applied to analyze the metal oxidation state in the carboranyl pincer complexes. Catalytic applications of (oCB-L1)Pd and (mCB-L1)Pd have shown the complexes are good catalyst precursors in Suzuki coupling in water and with very low amounts of catalyst loadings.

Direct access to pyrazolo(benzo)thienoquinolines. Highly effective palladium catalysts for the intramolecular C-H heteroarylation of arenes.

A short and atom-efficient strategy to obtain a series of pyrazolo(benzo)thienoquinolines is developed. Alternative catalytic systems for the key intramolecular direct heteroarylation of arenes are presented and include the first example of C-H (hetero)arylation of (hetero)arenes catalyzed by very low catalyst loadings of a palladium source.

An straightforward entry to new pyrazolo-fused dibenzo[1,4]diazepines.

A series of novel pyrazolodibenzo[1,4]diazepines has been synthesized with good overall yields. The diarylpyrazole intermediates, with structure similarity to biologically relevant compounds such as currently marketed drugs like rimonabant or celecoxib, were prepared by a tandem sequence amine-exchange/heterocyclization starting from readily available enaminones and arylhydrazines. The key step of this efficient methodology was C(aryl)-N bond construction, accomplished by a palladium-catalyzed intramolecular N-arylation reaction, which was conducted in both homogeneous and polymer-supported versions. Reaction scope of such protocols and recycling of the heterogeneous catalyst were also examined.

Ligand-free copper(I)-catalysed intramolecular direct C-H functionalization of azoles.

The first examples of copper-catalysed intramolecular direct C-arylation of azaheterocycles for the synthesis of complex heterofused compounds is presented, featuring an unprecedented arylation via C-H activation of 9H-purine and 4-azabenzimidazole.

Toward safer processes for C-C biaryl bond construction: catalytic direct C-H arylation and tin-free radical coupling in the synthesis of pyrazolophenanthridines.

A series of pyrazolo[1,5-f]phenanthridine derivatives has been efficiently synthesized by a short, straightforward sequence. A tandem amine-exchange/heterocyclization of enaminones was successfully applied to the regioselective preparation of 1,5-diarylpyrazole intermediates with structure resemblance to relevant nonsteroidal anti-inflammatory drugs such as celecoxib or tepoxalin. The final key step, cyclization by intramolecular biaryl bond formation, was accomplished by two alternative methodologies: radical coupling and catalytic direct arylation via C-H activation. The scope and limitations of the two methodologies have been explored and their complementariness has been established. In addition, polymer-supported heterogeneous catalysts have been compared with homogeneous analogues. In the radical process, toxic tin derivatives have been avoided in order to employ environmentally safer protocols.

A nonsymmetric pincer-catalyzed Suzuki-Miyaura arylation of benzyl halides and other nonactivated unusual coupling partners.

The catalytic activity of a PCN-type palladium pincer complex is evaluated in the construction of C(sp(2))-C(sp(2)) and C(sp(2))-C(sp(3)) bonds by Suzuki-Miyaura cross-couplings employing nontypical substrates such as benzyl halides, alpha-haloenones, or alkylboronic acids as coupling partners. Most of the reported reactions are achieved in aqueous media, with all of the advantages implied.

Palladium and copper-catalysed arylation reactions in the presence of water, with a focus on carbon-heteroatom bond formation.

Palladium and copper-catalysed arylation of amines, alcohols and thiols, powerful tools for the construction of C-N, C-O and C-S bonds, are typically carried out in organic (and often toxic) solvents. Therefore the use of such a sustainable, benign solvent as water in this context has gained growing attention. This tutorial review presents the most recent advances dealing with palladium and copper-catalysed carbon-heteroatom bond formation performed in total or partial aqueous media. The particular and distinctive features of water which are apparently responsible for the acceleration and greater chemoselectivity of the aqueous protocols will also be discussed.

[Progress in cardiac pacing 2006]. / Novedades en estimulación cardiaca 2006.

This article summarizes progress in cardiac pacing that has taken place in the last year, such as the incorporation of navigation technology into programmers, systems for monitoring hemodynamic parameters, and new developments in patient follow-up, principally home monitoring and the use of treatment guidelines. In addition, the article covers recent findings in resynchronization therapy, paroxysmal atrial fibrillation, and the management of patients with pacemakers who need to undergo magnetic resonance imaging.

Simple and efficient recyclable catalytic system for performing copper-catalysed S-arylation reactions in the presence of water.

A novel protocol for the copper-catalysed S-arylation of thiophenol derivatives with aryl halides leading to diaryl sulfides is reported. The reactions were catalysed by a combination of a copper salt and a 1,2-diamine derivative (acting both as the ligand and as the base) using exclusively water as the solvent. The recovery and successful reutilisation of the aqueous medium containing the active catalyst is described. Furthermore, one example of a "one-pot" process involving Br/I exchange of an aryl bromide and further S-arylation is presented.

Intramolecular PIFA-mediated alkyne amidation and carboxylation reaction.

The hypervalent iodine reagent PIFA promotes the intramolecular electrophilic cyclization of easily accessible alkynylamides and alkynyl carboxylic acids, leading to the formation of pyrrolidinone and lactone skeletons, respectively, in a very efficient way. A synthetic study and a mechanistic proposal for these transformations are presented.

Novedades en estimulación cardiaca 2006 / Progress in cardiac pacing 2006

En esta revisión se resumen los avances tecnológicos en estimulación cardiaca en el último año, como han sido la incorporación de navegadores a los programadores, los sistemas de detección de parámetros hemodinámicos y las novedades en el seguimiento, principalmente el seguimiento domiciliario y la guía terapéutica. Asimismo, se abordan los avances en resincronización, fibrilación auricular paroxística o el tratamiento actual de los pacientes portadores de marcapasos a los que se les desea realizar una resonancia magnética

This article summarizes progress in cardiac pacing that has taken place in the last year, such as the incorporation of navigation technology into programmers, systems for monitoring hemodynamic parameters, and new developments in patient follow-up, principally home monitoring and the use of treatment guidelines. In addition, the article covers recent findings in resynchronization therapy, paroxysmal atrial fibrillation, and the management of patients with pacemakers who need to undergo magnetic resonance imaging

Novel alternative for the N-S bond formation and its application to the synthesis of benzisothiazol-3-ones.

[reaction: see text] The synthesis of a series of benzisothiazolone derivatives starting from the readily available methyl thiosalicylate is presented. The key cyclization step features the formation of a N-acylnitrenium ion, generated by the hypervalent iodine reagent PIFA, and its succeeding intramolecular trapping by the thiole moiety leading to the construction of the title compounds by formation of a new N-S bond.

A metal-free approach to the synthesis of indoline derivatives by a phenyliodine(III) bis(trifluoroacetate)-mediated amidohydroxylation reaction.

A novel approach to the synthesis of indoline derivatives is presented. The key cyclization step features the phenyliodine(III) bis(trifluoroacetate)- (PIFA-) mediated formation of a N-acylnitrenium ion and its succeeding intramolecular trapping by the olefin fragment. In addition, difunctionalization of the alkene moiety is achieved since the in situ generation of an additional hydroxy group at the terminal position of the original double bond accompanies the intramolecular C-N bond formation.

Novel alternative for the N-N bond formation through a PIFA-mediated oxidative cyclization and its application to the synthesis of indazol-3-ones.

The synthesis of a series of N,N'-disubstituted indazolone derivatives starting from methyl anthranilates is presented. This general approach features a novel and easy way for access to the target N-heterocycles by formation of a new N-N single bond. The key cyclization step embraces the formation of an N-acylnitrenium intermediate, mediated by the hypervalent iodine reagent PIFA, and its succeeding intramolecular trapping by the amine moiety under rather mild experimental conditions.

On-water chemistry: copper-catalyzed straightforward synthesis of benzo[b]furan derivatives in neat water.

[reaction: see text] A more sustainable protocol leading to 2-alkyl- or 2-aryl-substituted benzo[b]furans is reported, involving a copper-TMEDA complex which catalyzes the transformation of readily available ketone derivatives into the corresponding benzofurans in good to excellent yields. The reaction is accomplished using water as the solvent without organic cosolvents, and one example of catalyst reutilization is also presented.