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A highly stereoselective ring opening of vinyl-substituted cyclic carbonates using water as a nucleophilic reagent gives (Z)-but-2-ene-1,4-diols.

A broad spectrum of substituted carbonate substrates is subjected to aminolysis in the presence of TBD.

The diastereoselective one-pot synthesis of hexahydrocyclopenta[b]pyrrole derivatives (bicycloprolines) has been achieved by base-mediated reactions of (E)-tert-butyl 6-bromo-2-hexenoate with α-imino esters. The catalytic asymmetric version of this process has been efficiently achieved using the CuI/(R)-DTBM-Segphos complex as a catalyst following a two-step 1,3-dipolar cycloaddition/intramolecular alkylation sequence.

Palladium catalysis enables the regioselective difunctionalization of alkenes using saccharin as the nitrogen source in the initial step of aminopalladation. Depending on the reaction conditions, diamination or aminooxygenation pathways can be accessed using hypervalent iodine reagents as the terminal oxidants. The aminooxygenation of allylic ethers originates from an unprecedented ambident behavior of saccharin. The participating palladium catalysts contain a palladium–saccharide unit. Two representative complexes of this type could be isolated and characterized.

Substituted epoxy alcohols and amines allow substrate-controlled conversion of CO2 into a wide range of heterocyclic structures through different mechanistic manifolds. This new approach results in an unusual scope of CO2-derived products by initial activation of CO2 through either the amine or alcohol unit, thus providing nucleophiles for intramolecular epoxy ring opening under mild reaction conditions. Control experiments support the crucial role of the amine/alcohol fragment in this process with the nucleophile-assisted ring-opening step following an SN i pathway, and a 5-exo-tet cyclization, thus leading to heterocyclic scaffolds.

The high platinum loadings required to compensate for the slow kinetics of the oxygen reduction reaction (ORR) impede the widespread uptake of low-temperature fuel cells in automotive vehicles. We have studied the ORR on eight platinum (Pt)–lanthanide and Pt-alkaline earth electrodes, Pt5M, where M is lanthanum, cerium, samarium, gadolinium, terbium, dysprosium, thulium, or calcium. The materials are among the most active polycrystalline Pt-based catalysts reported, presenting activity enhancement by a factor of 3 to 6 over Pt. The active phase consists of a Pt overlayer formed by acid leaching. The ORR activity versus the bulk lattice parameter follows a high peaked “volcano” relation. We demonstrate how the lanthanide contraction can be used to control strain effects and tune the activity, stability, and reactivity of these materials.

Trans carbamates have been prepared in a diastereoselective approach by a judicious one-pot combination of organic carbonates, prepared in situ, and suitable amine reagents under appropriate reaction conditions. This unprecedented approach allows for stereodivergence from a single oxirane substrate with easy access to both cis and trans carbamate isomers with high stereoselectivity (>19:1 d.r.). Key to the control of the diastereoselective nature of the conversions that lead to the trans carbamates is the in situ formation of trans-configured oligo/polycarbonates through Al catalysis, which provides the targeted products after aminolysis. The present results demonstrate the valorization of a renewable carbon-based reagent (CO2) into new valuable scaffolds and an unusual stereocontrol exerted through carbonate intermediates. A series of control experiments support the proposed mechanistic rationale towards the trans carbamate products, which is based on the trapping of an in situ formed trans-configured oligo/polycarbonate.

The chemoselective coupling of oxetanes and carbon dioxide to afford functional, heterocyclic organic compounds known as six-membered cyclic carbonates remains a challenging topic. Here, an effective method for their synthesis relying on the use of Al catalysis is described. The catalytic reactions can be carried out with excellent selectivity for the cyclic carbonate product tolerating various (functional) groups present in the 2- and 3-position(s) of the oxetane ring. The presented methodology is the first general approach towards the formation of six-membered cyclic carbonates (6MCCs) through oxetane/CO2 coupling chemistry. Apart from a series of substituted six-membered cyclic carbonates, also the unprecedented room-temperature coupling of oxetanes and CO2 is disclosed giving, depending on the structural features of the substrate, a variety of five- and six-membered heterocyclic products. A mechanistic rationale is presented for their formation and support for the intermediary presence of a carbonic acid derivative is given. The presented functional carbonates may hold great promise as building blocks in organic synthesis and the development of new, biodegradable polymers.

Depending on the catalyst either exo- or endo-products are obtained preferentially, usually with ≥98% d.e.

In nature, the commonly occurring reactive metal oxides of titanium, chromium, aluminium, and vanadium often chemically combine with the transition metal oxides such as iron oxides and form complex minerals. Physico-chemical separation of transition metal oxides from the remaining reactive metal oxides is therefore an important step in the purification of reactive oxide constituents. Each purification step has quite a high energy requirement at present. Current practice in industry yields sulphate and neutralized chloride waste from titanium dioxide enrichment, red mud from bauxite refining, slag and leach residues from vanadium extraction and chromite ore process residue (COPR) from chromate processes. In this review article, a novel alkali-based oxidative roasting and aqueous leaching for the extraction of mineral oxides is explained in the context of the original work of Le Chatelier in 1850, which was unsuccessful in the industrialization of bauxite processing for alumina extraction. However, much later in the 19th century the alkali-based oxidative mineral roasting was successfully developed for industrial scale manufacturing of chromate chemicals, which yields COPR. The crystal chemistry of mineral oxides, namely alumina, titanium dioxide, and chromium oxide in naturally occurring minerals is briefly reviewed in the context of chemical extraction, which is then developed as a model for developing thermodynamic chemical equilibrium principles for analyzing the physical separation and enrichment of such reactive metal oxides by forming water-soluble and water-insoluble alkali complexes. The involvement of the alkali roasting chemistry of non-magnetic titaniferous mineral waste is also reported in the initial separation of rare-earth oxide mixtures for subsequent separation of individual oxides. The paper concludes with a generic approach to process chemistry which minimizes waste generation and therefore helps in reducing the overall process and energy costs. Examples of recovering alkali from high pH solution using carbon dioxide are also demonstrated.

Efficient procedures are described for the reaction of cyclic epoxides with carbon dioxide to give cyclic carbonates generally with exclusive or high cis-diastereoselectivity.

A copper(II)-mediated diamination of 1,3-butadienes is reported. The reaction employs an inorganic base, copper dibromide as a reagent, and saccharin as the nitrogen source. The diamination proceeds for a series of 1,3-butadienes under relatively mild conditions with complete selectivity in favor of the 1,4-oxidation products.

The stereoselective construction of cyclopropane spirooxindoles is carried out by means of a vinylogous cascade reaction, integrating a vinylogous iminium ion/dienamine tandem sequence.

A convenient synthetic procedure for the preparation of chiral thiohydantoins derived from natural α-amino acids is reported. Salient features of this method include ready availability of the starting materials, mild reaction conditions, and high yields of the desired products. The prepared thiohydantoins were tested as organocatalysts in asymmetric Michael addition reactions, under solvent-free reaction conditions. Thiohydantoin 10 d turned out to be the most efficient catalyst, and its catalytic activity can be significantly enhanced by the use of an equimolar amount of salicylic acid as additive. Furthermore, highest diastereo- and enantioselectivity is achieved when the reaction is carried out at −5.5 °C, without detriment of the reaction rate. Regarding the reaction’s scope, the asymmetric Michael reaction catalyzed by 10 d was found to maintain its efficiency with various Michael acceptors. Se reporta un procedimiento conveniente para la preparacion de las tiohidantoinas quirales 10 a–f derivadas de α-aminoacidos y conteniendo el segmento de (S)-prolina. Caracteristicas sobresalientes de esta metodologia incluyen la alta disponibilidad de las materias primas, las condiciones de reaccion suaves y los altos rendimientos de los productos deseados. Los compuestos 10 a–f se probaron como organocatalizadores en la reaccion de adicion de Michael asimetrica, bajo condiciones de reaccion sin disolvente. La tiohidantoina 10 d resulto ser el catalizador mas eficiente, y su actividad catalitica mejora significativamente con el uso de una cantidad equimolar de acido salicilico como aditivo. Ademas, se consigue una mayor diastereo- y enantioselectividad cuando la reaccion se lleva a cabo a −5.5 °C, sin detrimento de la velocidad de reaccion. En cuanto al alcance de la reaccion, se encontro que en general la reaccion de Michael asimetrica catalizada por 10 d mantiene su eficacia con varios aceptores de Michael.

α-Heteroarylpyrrolidines have been efficiently prepared via 1,3-dipolar cycloaddition between silylimines and activated olefins. In the presence of Cu(CH3CN)4PF6/Walphos as catalytic system, high levels of enantioselectivity (up to ≥99% ee) and diastereoselectivity were achieved (major formation of C-2/C-4 trans-substituted pyrrolidines). The reaction is compatible with a broad variety of dipolarophiles including maleimides, maleates, fumarates, nitroalkenes, and vinylsulfones. The resulting cycloadducts can be transformed into bioactive pyrrolidine derivatives.

Al(III) complexes of amino-tris(phenolate) ligand scaffolds (I) are prepared to attain effective Lewis acidic catalysts.

In the presence of fluoroform-derived CuCF3 a wide range of aromatic iodides and bromides are found to undergo trifluoromethylation with high chemoselectivity and efficiency.

The (+)-α-pinene derived N-protected amino acid (I) is used in the synthesis of several constrained pyrrolidine derivatives.

The stereochemical outcome of the reaction is determined by the configuration of the substrate.

The synthesis of new dinuclear iodine(III) compounds and their application in the intermolecular diamination of alkenes are described.

An aluminum complex based on an amino triphenolate ligand scaffold shows unprecedented high activity (initial TOFs up to 36 000 h–1), broad substrate scope, and functional group tolerance in the formation of highly functional organic carbonates prepared from epoxides and CO2. The developed catalytic protocol is further characterized by low catalyst loadings and relative mild reaction conditions using a cheap, abundant, and nontoxic metal.

The presented new enantioselective direct vinylogous aldol reaction of cyclohexenone with various α-keto esters uses the bifunctional primary amine-thiourea catalyst ATU.

The method employs catalytic amounts of potassium bromide and sodium chlorite as oxidant and avoids any use of transition metal catalyst.

Diels—Alder reaction of various keto-containing dienophiles and 3-(2-methylindol-3-yl)acrylaldehydes leads to the stereoselective formation of tetrahydrocarbazoles.

Trifluoromethylation of various aryl iodides is achieved using two new Cu(I) trifluoromethylating agents (I) and (IV).

Bis(2,4,6-trimethoxybenzonitrile)gold(I) hexafluoroantimonate is shown to be an air stable, highly versatile precatalyst of active and robust gold complexes which catalyze the cyclopropanation of enyne (I), the methoxy cyclization of enyne (IV), and the skeletal rearrangement of enyne derivatives (IV) and (VIII).

An enantioselective aza-Michael reaction for the preparation of a series of indoline amino acid esters (II) and (IV) from corresponding alkenes (I) and (III), resp., is elaborated using well defined ruthenium sulfonamide complexes as catalyst.

Both pyridine systems and a p-nitroaryl substituent are essential for a successful reaction.

Three distinct aminocatalytic cascade reactions leading to enantiomerically pure spirocyclic benzofuranones ar developed.

(Z)- and (E)-2-alkoxyindolenines (V) and (VI) are synthesized by treating bromoindole (II) with alcohols in the presence of molecular sieves.

The result of the indirect electrochemical oxidation of cyclic ketones in methanol in an undivided cell in the presence of sodium halides depends on the ring size of ketone and the type of mediator. Selectivity of the reaction in some cases and current efficiency are increased by addition of supporting electrolyte - sodium hydroxide. Formation of cyclic 2,2-dimethoxycycloalkanols and the electrochemically induced Favorskii rearrangement with the formation of methyl cycloalkencarboxylates containing in the ring one carbon atom less than starting ketone are the main ways of the indirect electrochemical oxidation of cyclic ketones.

Cycloaddition of benzyne to 2-pyrones affords the corresponding naphthalene derivatives, the intermediate bicyclic adduct not being detected. Benzopyrones do not react with benzyne under similar conditions probably because this would require the fused aromatic ring to lose aromaticity in the Diels-Alder transition state, which is therefore destabilized. 4-Bromo-2-naphthoic acid methyl ester (obtained by cycloaddition of benzyne to 3-bromo-5-carboxymethylpyran-2-one) can be transformed into 3,3′-dicarboxymethyl-1,1′-binaphthyl by Ni-mediated dimerization.

The monoterpene alkaloid (±)-actinidine 10 is prepared in 5 steps from 3,4-dimethylpyridine using a pyridine radical cyclisation for the formation of the cyclopentano[c]pyridine skeleton.

Found at the core of many discotic liquid crystals, triphenylenes can now be synthesized efficiently by the palladium-catalyzed trimerization of arynes, including those containing donor and acceptor substituents [Eq. (a); R=OMe, F].

The allylation and propargylation of 3-bromo-4-formylpyridine under zinc-mediated Barbier conditions is described. The homoallylic alcohols produced are cyclised via the derived 3-pyridyl radical to give cyclopentannulated pyridines. One of these bicyclic compounds is converted into an advanced intermediate in a previous synthesis of the monoterpene alkaloid (±)-oxerine.

The formation and structure of the title aggregates are paradigms of the self-assembly of amphiphilic molecular building blocks in supramolecular chemistry. This review summarizes the research in the University of Barcelona on the homoassociation of the water soluble meso 4-sulfonatophenyl-and phenyl substituted porphyrins.