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Cascade reactions involving nitrones and allenes are known to facilitate the rapid synthesis of several indole derivatives. The chemoselectivity of these complicated transformations can be influenced by substrate functionalization, reaction conditions, and catalyst control. While seminal studies established primary reactivity patterns, recent work has illustrated the impact of these cascade reactions for creating diverse libraries, increased the breadth of these methods with facilitated access to challenging nitrones, and shown that these transformations can be controlled by asymmetric catalysis.

A method for the synthesis of a large number of 1,2-benzothiazines bearing pyridyl as well as carbonyl groups is developed from rhodium-catalyzed carbene insertions into aromatic C–H bonds of S-aryl sulfoximines using pyridotriazoles by denitrogenative cyclization followed by the elimination of alcohols. The present method involves the N–H/C–H activation of simple alkyl aryl sulfoximines and has the advantages of a broad substrate scope, high functional group tolerance, and good regioselectivity.

Two new substituted polyoxotantalate clusters, [Ti2 Ta8 O28 ](8-) and [Ti12 Ta6 O44 ](10-) , considerably expand the pH range where tantalates persist in aqueous solution. The structures of [Ti2 Ta8 O28 ](8-) and [Ti12 Ta6 O44 ](10-) are reported as tetramethylammonium salts after synthesis at hydrothermal conditions in aqueous solution. These Ti-substituted polyoxotantalate clusters have analogues among recently discovered niobates, but are slightly larger and more persistent in solution. Most importantly, they exhibit a much wider range of pH stability than the familiar hexatantalate cluster, which is the only other tantalate known to be stable at highly basic pH conditions. These molecules are kinetically stable to near-neutral pH, making them excellent synthons for further development into materials and catalysts, and an significant advance in adapting tantalates for use in aqueous solutions.

Pyrrolo[2,1-f][1,2,4]triazin-4(3H)-ones 12 have been easily prepared via nucleophile-induced rearrangement of pyrrolooxadiazines 11 and regioselective intramolecular cyclization of 1,2-biscarbamoyl-substituted 1H-pyrroles 10. In this work, we demonstrated that the described synthetic approaches can be considered to be more facile and practical than previously reported procedures.

2-(2-Bromophenyl)-1H-indoles are carbonylatively cyclized under carbon monoxide pressure in toluene in the presence of a catalytic amount of PdCl2 and PPh3 along with a base to give 6H-isoindolo[2,1-a]indol-6-ones in high yields.

2-(2-Bromovinyl)benzimidazoles are carbonylatively cyclized under carbon monoxide pressure in toluene in the presence of a catalytic amount of PdCl 2 and PPh 3 along with a base to give 1 H -benzo[ d ]pyrrolo[1,2- a ]imidazolones in good yields.

Rh(III)-catalyzed tandem ortho C-H olefination of cyclic 4-aryl sulfamidates (1) and subsequent intramolecular cyclization are described. This reaction serves as a method for the direct and stereoselective synthesis of 1,3-disubstituted isoindolines (3) starting with enantiomerically enriched 4-aryl cyclic sulfamidates. In this process, the configurational integrity of the stereogenic center in the starting cyclic sulfamidate is completely retained. In addition, the process generates trans-1,3-disubstituted isoindolines exclusively.

A variety of flavones were expediently synthesized from readily accessible chromanones via a one-pot sequence involving Pd(II)-catalyzed dehydrogenation and oxidative boron-Heck coupling with arylboronic acid pinacol esters. In particular, the use of arylboronic acid pinacol esters was found to significantly improve the yield of the reaction.

The structure and absolute stereochemistry of cristazine (I), a new class of dioxopiperazine alkaloid, is presented.

Rutaecarpine is a pentacyclic indolopyridoquinazolinone alkaloid found in Evodia rutaecarpa and other related herbs. It has a variety of intriguing biological properties, which continue to attract the academic and industrial interest. Studies on rutaecarpine have included isolation from new natural sources, development of new synthetic methods for its total synthesis, the discovery of new biological activities, metabolism, toxicology, and establishment of analytical methods for determining rutaecarpine content. The present review focuses on the synthesis, biological activities, and structure-activity relationships of rutaecarpine derivatives, with respect to their antiplatelet, vasodilatory, cytotoxic, and anticholinesterase activities.

Two new dimeric monoterpene-linked coumarin glucosides, paratrimerins A (1) and B (2), and three known coumarins, 6-(6-hydroxy-3,7-dimethylocta-2,7-dienyl)-7-hydroxycoumarin (3), ostruthin (4), and ninhvanin (5), were isolated from the roots and stems of Paramignya trimera (OLIV.) GUILL. collected in Khanh Hoa province, Vietnam. Compound 1 comprises two 7-O-β-D-glucopyranoside coumarins linked at positions 6,6' via a 1,3,4,4-tetrasubstituted cyclohexene containing a monoterpene bridge, whereas compound 2 is a β-D-apiofuranosyl(1→6)-β-D-glucopyranosyl derivative of 1. The chemical structures of these compounds were determined by one dimensional (1D) and 2D-NMR and high resolution-electrospray ionization (HR-ESI)-MS spectroscopy.

An efficient method for the synthesis of heterogeneous gold catalysts has been developed. These catalysts were easily assembled from readily available silica materials and gold complexes. The heterogeneous catalysts exhibited superior reactivity in various reactions where protodeauration is the rate-limiting step. Dramatic enhancement in regio- and enantioselectivity was observed when compared to the homogeneous unsupported gold catalyst. The catalysts are easily recovered and recycled up to 11 times without loss of enantioselectivity.

Metal dodecaborates M_2/_nB_(12)H_(12) (n denotes the valence of the metal M), containing icosahedral polyatomic anion [B_(12)H_(12)]^(2−), have been attracting increasing interest as potential energy materials, especially in the context of hydrogen storage and superionic conductivity. M_2/_nB_(12)H_(12) are commonly formed as dehydrogenation intermediates from metal borohydrides M(BH_4)_n, like LiBH_4 and Mg(BH_4)_2, which are well-known as potential high-density hydrogen storage materials. The strong B−B bond in the icosahedral [B_(12)H_(12)]^(2−), however, is regarded to be the key factor that prevents the rehydrogenation of dodecaborates. In order to elucidate the mechanism as well as to provide effective solutions to this problem, a novel solvent-free synthesis route of anhydrous M_2/nB_(12)H_(12) (here M means Li, Na, and K) has been developed. Thermal stability and transformations of the anhydrous single phase Li_2B_(12)H_(12) suggested the formation of the high temperature polymorph of Li_2B_(12)H_(12) during the dehydrogenation of LiBH_4, while concurrently emphasized the importance of further investigation on the decomposition mechanism of metal borohydrides and metal dodecaborates. The high stability of icosahedral [B_(12)H_(12)]^(2−), on the other hand, favors its potential application as solid electrolyte. Recently, Na^+ conductivity of Na_2B_(12)H_(12) was reported to be 0.1 S/cm above its order−disorder phase transition at ∼529 K, which is comparable to that of a polycrystalline β”-Al_2O_3 (0.24 S/cm at 573 K) solid state Na-electrolyte. Mechanistic understanding on the diffusion behavior of cation and further improvement of ionic conductivity at a lower temperature, however, are important in order to facilitate the practical application of metal dodecaborates as superionic conductors.

Diversely substituted oxindoles were obtained from atom economical direct C–C bond formation reactions of various substituted anilides and pyridinylamides with metal salts and oxides. The catalysts include CuO, Cu2O, FeCl3, Fe2O3, TiO2, ZnO, and Ag2O and their nanoparticles. The reaction proceeds under solvent-free and aerobic conditions in excellent yields. The reaction mechanism was proved to be a single electron transfer pathway with oxygen as the re-oxidant of the metal catalysts.

A synthetic route to a wide range of 2-alkoxyaryl-2-aryl enamines is developed from Rh-catalyzed alkoxyarylation of N-sulfonyl-4-aryl-1,2,3-triazoles with aryl ethers via the elimination of nitrogen molecule. In addition, 2-alkoxyaryl-2-aryl enamines are prepared via tandem Cu-catalyzed cycloaddition and Rh-catalyzed alkoxyarylation starting from alkynes, N-sulfonyl azides, and aryl ethers in one-pot.

Polyoxoniobate clusters that are stable in acidic solutions are rare and particularly useful in industrial processes. Here we report a new pentaphosphate niobate polyoxometalate cluster (TMA)9H3Nb9P5O41·28H2O (Nb9P5) that is stable over a wide pH range and that can be converted reversibly into the peroxo form.

A synthetic method of a wide range of cinnolin-3(2H)-one derivatives is developed from the reaction of symmetrical as well as unsymmetrical azobenzenes with diazotized Meldrum’s acid via Rh-catalyzed C–H alkylation followed by cyclization.

The reaction provides a new method for synthesizing pyrimidines starting from readily available ketones and amidine hydrochloride.

The title compounds are obtained by Rh-catalyzed cyclization of triazoles with bromocyanide (II).

An efficient phosphaannulation via palladium(II)-catalyzed CH activation/oxidative cyclization by the 6-endo mode is reported for the synthesis of 3-substituted phosphaisocoumarins from the reaction of arylphosphonic acids with unactivated alkenes under aerobic conditions. Also, α,α-disubstituted benzylphosphonic acids were phosphaannulated with unactivated alkenes, producing phosphaisochromanones having (Z)-alkylidenyl groups via anti-phosphoryloxypalladation by the 6-exo mode.

(Me4N)5 [HNb4P2O14(O2)4] ·9H2O (I) is prepared by hydrothermal reaction of Nb2O5, Me4NOH, and H3PO4 (autoclave, 130 °C, 16 h) followed by addition of 30% aq.

A variety of activated as well as nonactivated alkenes react with the title compounds via aerobic oxidative Heck reactions to 3-alkenylphosphacoumarins.

A range of arylmethyl-substituted pyrrolidines and tetrahydrofurans were produced by FeCl2-catalyzed tandem cyclization and cross-coupling reactions of alkyl iodides and aryl Grignard reagents. The substituents on alkenes had a profound effect on the progress of the tandem reactions, with di- and tri-substituted alkenes affording cyclized pyrrolidines. Several experimental results, such as cyclopropyl ring opening, the stereochemical outcome of the reaction with a secondary iodide substrate, and intermediate identification with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), support the conclusion that a radical process is involved in this catalytic system. Moreover, deuterium labeling experiments indicated that radical disproportionation could occur in the termination reactions of the cyclized alkyl radical species.

Bi2O2Te is prepared by solid state reaction of a stoichiometric mixture of Bi, Bi2O3, and Te (evacuated silica tubes, 873 K, 10 h; complex heating schedule).

β-Bromo-α,β-unsaturated carboxylic acids were coupled and cyclized with 1,3-diketones by microwave irradiation in the presence of a catalytic amount of copper powder and base to give the corresponding 2H-pyran-2-ones in good to high yields.

Mild conditions and a short reaction time result in a successful preparation of the title compounds, required as important synthetic intermediates.

Polyethylene glycol was found to be an inexpensive non-toxic and effective medium for the one-pot synthesis of benzo[a]xanthen-11-ones in the presence of TiO2–SiO2 as the catalyst in good to excellent yield. The salient features of this protocol are the simplicity of the procedure, the ready accessibility of the catalyst, its cost effectiveness, and reusable catalyst in relatively short reaction times.

A new method for the synthesis of 1,4-enamino ketones through rearrangement of dialkenylhydroxylamines generated in situ by addition of N-alkenylnitrones to allenes is described.

The described synthesis starts from the commercially available furan-3-one derivative (I) which undergoes a reductive dehydration and conversion to a triflate derivative.

A palladium-catalyzed cyclization reaction of aryl halides containing an allylic moiety leads to azepine skeletons.

Dynamic kinetic resolution driven, asymmetric transfer hydrogenation reactions of a wide range of 2-substituted α-alkoxy-β-ketophosphonates 3 were observed to proceed efficiently to give the corresponding 2-substituted α-alkoxy-β-hydroxy phosphonates 4 with excellent levels of diastereo- and enantioselectivity. These processes are promoted by using well-defined, commercially available, chiral transition metal catalysts and a 0.2:1 mixture of formic acid and triethylamine as the hydrogen source and solvent.

Ring opening of chiral aziridines (I) with Et3N·3HF gives both possible regioisomeric fluoroamines in ratios depending on the C-2 substituent in the starting aziridine.

ConspectusThe importance of spin state changes in organometallic reactions is a topic of significant interest, as an increasing number of reaction mechanisms involving changes of spin state are consistently being uncovered. The potential influence of spin state changes on reaction rates can be difficult to predict, and thus this class of reactions remains among the least well understood in organometallic chemistry. Ultrafast time-resolved infrared (TRIR) spectroscopy provides a powerful tool for probing the dynamics of spin state changes in organometallic catalysis, as such processes often occur on the picosecond to nanosecond time scale and can readily be monitored in the infrared via the absorptions of carbonyl reporter ligands. In this Account, we summarize recent work from our group directed toward identifying trends in reactivity that can be used to offer predictive insight into the dynamics of coordinatively unsaturated organometallic reaction intermediates.In general, coordinatively unsaturated 16-...

Size controlled LiNi0.8Co0.15Al0.05O2 cathode powders are prepared by co-precipitation followed by calcination between 750 and 850 °C.

β-Bromo α,β-unsaturated carboxylic acids were coupled and cyclized with amidine hydrochlorides by microwave irradiation in the presence of catalytic amounts of copper powder and a base to give the corresponding pyrimidinones in high yields.

The first access to (R)-configured epoxides from para-substituted styrenes in excellent stereoselectivity, using enzyme catalysis is revealed.

Pd-nanoparticles deposited inside silica nanotubes efficiently catalyze cross coupling reactions of aryl halide (II) and thiazoles (IV) with arylboronic acids in water.

Especially, nanocompositesbetween transient metal oxides and ordered mesoporouscarbon (OMC) have become more attractive due to theirbeneficial characteristics: i) abundant lithium storage sitesand fast lithium diffusion in nanosized metal oxides andOMC; ii) facile electrolyte penetration owing to orderedmesopores iii) higher electric conductivity through carbonframework.

The Lindqvist-type compound (NMe4)5 [H2TeNb5O19]·20H2O is prepared by hydrothermal reaction of Te(OH)6, Nb2O3, and (NMe4)OH (autoclave, 110 °C, 5 d).