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The introduction of a chlorine atom to a carbon center in an enantioselective manner via conventional C–Cl bond formation is difficult. Here we report a new approach to this class of tertiary alkyl chlorides with high optical purities. Instead of forming a new C–Cl bond, our approach involves carbene-catalyzed desymmetrization of 2-chloro-1,3-diols as the key step to set up the chiral carbon center with excellent enantiomeric excess.

We are reporting a regioselective and stereoselective route to N2-β-tetrazolyl aromatic donor/acceptor unnatural nucleosides as new class of possible DNA base analogs. The SN2 substitution reaction at the anomeric center of Hoffer's chlorosugar with various 5-substituted aromatic tetrazoles in THF in presence of K2CO3 proceeds with regioselectivity at N2-tetrazoles and stereoselectivity at α-chlorosugar with very good yield. The stereoelectronic and steric effects play a crucial role for the observed outcome which is also supported from a theoretical (DFT) study. The methodology is simple, eco-compatible and the tetrazolyl unnatural nucleosides might find applications in decorating DNA for various biotechnological and DNA based material science applications.

Chromenes (benzopyrans) which are components of many biologically active compounds1,2 are of increasing significance. They are used as anti-hypertensive,3 hypoglycemic,4 cardio-protective5, anti-tu...

The authors gratefully acknowledge the Royal Society (University Research Fellowship to C.S.J.C) for funding.

The reaction between nitriles and aminoalcohols to access 2-substituted oxazolines was investigated. Using copper-NHC complexes, various nitriles were successfully converted into the corresponding oxazolines, under milder and less wasteful conditions than those of previously reported methods.

The synthesis and characterization of abnormal N-heterocyclic carbene, cyclic (alkyl)(amino)carbene, and mesoionic carbene copper(I) complexes are reported. These organometallic species are obtained via a versatile and inexpensive synthetic pathway using readily available reactants, namely copper oxide and iminium salts. The catalytic activity of this series of complexes was evaluated in the [3+2] cycloaddition of alkynes with azides (CuAAC). Outstanding catalytic properties were observed for the abnormal NHC- and triazolylidene-based copper(I) complexes.

A chiral disulfonimide (DSI)-catalyzed asymmetric reduction of N-alkyl imines with Hantzsch esters as a hydrogen source in the presence of Boc2 O has been developed. The reaction delivers Boc-protected N-alkyl amines with excellent yields and enantioselectivity. The method tolerates a large variety of alkyl amines, thus illustrating potential for a general reductive cross-coupling of ketones with diverse amines, and it was applied in the synthesis of the pharmaceuticals (S)-Rivastigmine, NPS R-568 Hydrochloride, and (R)-Fendiline.

Although the chemistry of copper has a long history [1a-d] , the relatively recent discovery of N-heterocyclic carbene (NHC) as transition-metal supporting ligands has permitted novel vistas to be explored in copper reactivity and catalysis [1e,f] . Shortly after the seminal discovery of Arduengo, Raubenheimer reported a neutral copper carbene complex [1] , [2] . However, the field remained dormant for almost ten years. In the early 2000s, new breakthroughs were achieved: first, the synthesis of NHC–copper using Cu2O was reported by Danopoulos and followed by the first application in catalysis by Woodward [3] , [4] . The work by Buchwald and Sadighi appeared next, where the first catalysis using a well-defined complex was described [5] . The first reports in this field were based on systems used to mimic their phosphine relatives. NHCs have become ligands of significant interest due to their steric and electronic properties [6] , [7] , [8] . Combining the NHC ligand family and copper became, for some, an obvious and productive area [6] . Over the last decade alone, numerous systems have been developed. Copper–NHC complexes can be divided into two major classes: neutral mono-NHC and cationic bis-NHC derivatives: [Cu(X)(NHC)] [9] (X = halide, acetate, hydroxide, hydride, etc.) and [Cu(NHC)(L)][Y] (L = NHC or PR3; Y = PF6, BF4) [10] . The neutral-halide-bearing complexes have been widely used in catalysis, mainly due to their ease of synthesis [9] . In addition to halide-bearing complexes, notable important related compounds have been reported: Nolan and co-workers disclosed the first hydroxide derivative [Cu(OH)(IPr)] (IPr = N,N’-bis(2,6-di-isopropylphenyl)imidazol-2-ylidene) and Sadighi published alkoxides, hydrides and borate species, which permitted novel reactivity to be explored [9g-i] . With respect to cationic derivatives, homoleptic and heteroleptic bis-NHC complexes have been reported and have been efficiently used in catalysis allowing important improvements [10] . In this review, an overview of the two classes and their respective catalytic performance will be presented.

Two new and efficient dual catalytic procedures for the synthesis of tri- and tetrasubstituted alkenes using aryl bromides and chlorides are reported. The formation of these vinyl arenes occurs independently in a one-pot relay and a one-pot cooperative procedure using well-defined Pd and Cu N-heterocyclic carbene (NHC) complexes. Mechanistic studies were performed to elucidate the key role of the solvent in each procedure as well as the formation of the key intermediate, [Cu(alkenylboron)(NHC)], which allows transmetalation with the Pd-NHC co-catalyst in the cooperative catalysis.

Esterification of acid 2 with 2-hydroxyacetophenones 1 yielded compounds 3 which have been converted to β-diketones 4 by Baker-Venkatraman transformation. A series of 2-substituted chromones 5 have been obtained by acid catalysed intramolecular cyclization of β-diketones. Substituted pyrazoles 6 have been obtained from chromones 5. All the synthesized compounds have been confirmed by the spectroscopic techniques. Chromones and pyrazoles have been evaluated for their antibacterial and antifungal efficacy.

New compounds (IIa) and (IIb) exhibit promising antibacterial activities against Escherichia coli, Salmonella typhii, Bacillus subtilis and Staphylococcus aureus.

The title thiazolines (III) (25 examples) are obtained by base-catalyzed reaction of various nitriles (I) and cysteamine hydrochloride (II) under solvent-free conditions.

The title compound is characterized by high-pressure powder XRD and Raman scattering measurements up to 22 GPa, and by DFT calculations.

In this short review, we focus on the synthesis and applications of new phosphite-bearing ruthenium complexes in olefin metathesis. These complexes were designed to take advantage of a known synergistic effect between strong σ-donating NHC ligands and π-acidic phosphites. The resulting catalysts display higher stability compared to their phosphine-containing congeners. A comparative summary of their use in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization, as well as DFT calculations describing our mechanistic understanding, are presented.

Na2Li2Ti6O14 is prepared by an optimized molten salt synthesis via reaction of Na2CO3, Li2CO3 (5-20% excess to compensate for Li evaporation), and TiO2 in a eutectic NaCl/KCl flux (Al2O3 crucible, 700—900 °C, 2—16 h).

Two-dimensional (2D) materials have attracted a great deal of interest in recent years. This family of materials allows for the realization of versatile electronic devices and holds promise for next-generation (opto)electronics. Their electronic properties strongly depend on the number of layers, making them interesting from a fundamental standpoint. For electronic applications, semiconducting 2D materials benefit from sizable mobilities and large on/off ratios, due to the large modulation achievable via the gate field-effect. Moreover, being mechanically strong and flexible, these materials can withstand large strain (>10%) before rupture, making them interesting for strain engineering and flexible devices. Even in their single layer form, semiconducting 2D materials have demonstrated efficient light absorption, enabling large responsivity in photodetectors. Therefore, semiconducting layered 2D materials are strong candidates for optoelectronic applications, especially for photodetection. Here, we review the state-of-the-art in photodetectors based on semiconducting 2D materials, focusing on the transition metal dichalcogenides, novel van der Waals materials, black phosphorus, and heterostructures.

We review different electron transport methods to probe the magnetic properties, such as the magnetic anisotropy, of an individual Fe4 SMM. The different approaches comprise first and higher order transport through the molecule. Gate spectroscopy, focusing on the charge degeneracy-point, is presented as a robust technique to quantify the longitudinal magnetic anisotropy of the SMM in different redox states. We provide statistics showing the robustness and reproducibility of the different methods. In addition, conductance measurements typically show high-energy excited states well beyond the ground spin multiplet of SMM. Some of these excitations have their origin in excited spin multiplets, others in vibrational modes of the molecule. The interplay between vibrations, charge and spin may yield a new approach for spin control.

In this article, an overview of the application of selected metal nitrides as ammonia synthesis catalysts is presented. The potential development of some systems into nitrogen transfer reagents is also described.

A well-defined dimeric Pd-complex bearing a sterically very demanding NHC-ligand is synthesized, which appears to be the most active Pd-precatalyst reported to date for the synthesis of tetra-ortho-substituted biaryl compounds (18 examples) via cross-coupling of sterically demanding aryl halides with Grignard reagents.

Ultralow-density, ultra-high suface area Al2O3 and TiO2 bulk materials with interconnected nanotubular morphology are synthesized.

For the first time aminocatalyzed α-alkylation of α-branched aldehydes with benzyl bromides is developed.

A series of Pd dimers bearing an N-heterocyclic carbene ligand was studied in the Mizoroki–Heck reaction. [Pd(μ-Cl)Cl(SIPr)]2 (SIPr = {N,N′-bis[2,6-(diisopropyl)phenyl]imidazolidin-2-ylidene}) was shown to be highly efficient in this cross-coupling for a range of aryl and heterocyclic bromides, with low palladium loading (20–200 ppm).

Homogeneous Pd(0) complexes are powerful tools for numerous catalytic reactions. Recent work has demonstrated the unique properties displayed by [Pd(NHC)(PR3)] catalysts in the activation of ammonia borane (AB) and formic acid, with the subsequent formation of hydrogen. An understanding of the mechanism allowed for the design of a new dehydrogenation–hydrogenation tandem process using ‘hydrogen storage materials’. The hydrogenations of alkenes and alkynes were successfully performed at low catalyst loadings of Pd(0) species and mild conditions. Such tandem process represents a safe and innovative alternative to classic hydrogenation protocols.

Five sequences demonstrate the usefulness for the construction of a range of bi- and tricyclic functionalized lactones with control of stereochemistry and a minimum of synthetic steps, involving an acid-catalyzed cyclopropylester to γ-lactone skeletal rearrangement.

N-Heterocyclic carbene ligated copper complexes act as catalysts in a variety of reactions. A brief overview of this rich chemistry is given here. Of particular note is the ability of Cu(NHC) complexes to functionalize carbonyls, alkenes and alkynes. With growth in the number of Cu(NHC) derived complexes, the catalytic possibilities involving these complexes are ever growing. We feel the full potential of these (for the most part) simply accessed complexes has yet to be fully achieved. The litany of reactions which Cu(NHC) catalyst facilitate are outlined here.

A highly efficient catalytic system for the tandem dehydrogenation of ammonia borane coupled with hydrogenation of alkenes (I), enones (III), and alkynes (V) is described.

The described pre-catalyst can be used with di- and trisubstituted dienes in ring-closing metathesis reactions achieving high yields.

This review discusses the synthesis and application of glycosyl thioimidates in chemical glycosylation and oligosaccharide assembly. Although glycosyl thioimidates include a broad range of compounds, the discussion herein centers on S-benzothiazolyl (SBaz), S-benzoxazolyl (SBox), S-thiazolinyl (STaz), and S-benzimidazolyl (SBiz) glycosides. These heterocyclic moieties have recently emerged as excellent anomeric leaving groups that express unique characteristics for highly diastereoselective glycosylation and help to provide a streamlined access to oligosaccharides.

The use of a mixed phosphite/N-heterocyclic carbene bearing ruthenium precursor permits the synthesis of unprecedented four-coordinate Ru(II) and Ru(III) cationic complexes adopting an unusual sawhorse structure.

A novel ruthenium phosphite complex is prepared and efficiently applied as catalyst in ring closing metatheses of alkenes (I), (III), and (V).

Gold(I)-aryl complexes (III) are synthesized under mild conditions from a gold(I) hydroxo precursor without the need for silver co-catalysis.

A facile synthesis of variously substituted pyrroles is achieved by 5-endo-dig cyclization of 3-alkynyl-hydroxyalkanamine derivatives and subsequent in situ dehydration of the resulting hydroxy-dihydropyrroles.

The major constituents of leaf extracts of Iris fulva KER GAWL. comprised a known flavone C-glycoside, 5,4′-dihydroxy-7-methoxyflavone-6-C-(6‴-O-(E)-p-coumaroyl-β-glucopyranosyl)(1‴→2″)-β-glucopyranoside (1) and the new monoterpene glycoside, linalyl-6′-O-(3″-hydroxy-3″-methylglutaroyl)-β-D-glucopyranoside (2), both of which were prominent components of Iris brevicaulis RAF. leaf extracts. The structure of a new polyacylated sucrose derivative (3a) obtained from the rhizomes of I. fulva was elucidated as 3-O-(E)-p-coumaroyl-β-D-fructofuranosyl-(2↔1′)-[2″,4″,6″-tri-O-acetyl-β-D-glucopyranosyl-(1″→3′)-(2′,6′-di-O-acetyl-4′-O-(E)-p-coumaroyl-α-D-glucopyranoside)]. Selective hydrolysis of the 4″-O-acetyl moiety of the terminal β-glucopyranosyl residue of 3a occurred after several hours in solution giving 3-O-(E)-p-coumaroyl-β-D-fructofuranosyl-(2↔1′)-[2″,6″-di-O-acetyl-β-D-glucopyranosyl-(1″→3′)-(2′,6′-di-O-acetyl-4′-O-(E)-p-coumaroyl-α-D-glucopyranoside)] (3b), which subsequently underwent further deacetylation.

The title compound is synthesized by solid state reaction of stoichiometric amounts of V2O5 and Cr2O3 at 630 °C and its crystal structure is determined by powder XRD.

Transition-metal-mediated carboxylation of N H and C H bonds represents a nascent area in organic chemistry, because these reactions enable the efficient construction of valuable synthons. Palladium-catalyzed N-carbonylation–oxidation sequences are well-documented, but they often require high catalyst loadings and the use of either gaseous carbon monoxide or Group VI metal–carbonyl complexes. An analogous transformation sequence is also promoted by molybdenum and tungsten carbonyl amine species under forcing temperatures. Important advances in C-carboxylation reactions have been made using ruthenium and nickel complexes; however, examples under mild conditions are elusive. The carboxylation of allylstannanes, organozincs, and organoboronic esters have been described as a new method to improve functional group tolerance, but the stoichiometric consumption of an organometallic reagent remains a disadvantage. The reactivity of allylstannanes and organozinc compounds necessitates handling under an inert atmosphere, while organoboronic esters are expensive. A protocol has recently been developed for the C-carboxylation of simple aromatic groups under very mild reaction conditions. In this case the strongly basic [Au(IPr)(OH)] (IPr=1,3-bis(diisopropyl)phenylimidazol-2-ylidene) complex (pKaDMSO= 30.3(2)) was used, [11] which contains an N-heterocyclic carbene (NHC) ligand [Eq. (1)].

Novel ruthenium complexes are prepared and tested as catalysts in ring closing and cross-metathesis.

Catalysts generated by the addition of carbon, nitrogen or phosphorus to transition metals have interesting properties and potential applications. The addition of carbon, nitrogen or phosphorus can lead to substantial modification of the catalytic efficacy of the parent metal and some carbides and nitrides are claimed to be comparable to noble metals in their behaviour. Amorphous boron transition metal alloys are also a class of interesting catalyst, although their structures and phase composition are more difficult to define. In this critical review, the preparation of these catalysts is described and brief details of their application given. To date, attention has largely centred upon the application of these materials as alternatives for existing catalysts. However, novel approaches towards their utilisation can be envisaged. For example, the extent to which it is possible to utilise the “activated” carbon and nitrogen species within the host lattices of carbides and nitrides, respectively, as a reactant remains largely unexplored (195 references).