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.

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.

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.

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.

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.