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We show that latent oxalyl thioester surrogates are a powerful means to modify peptides and proteins in highly dilute conditions in purified aqueous media or in mixtures as complex as cell lysates. Designed to be shelf‐stable reagents, they can be activated on demand to enable ligation reactions with peptide concentrations as low as a few hundred nM at rates approaching 30 M−1 s−1. [ABSTRACT FROM AUTHOR]

A series of new trivalent rare-earth allyl-borohydride complexes with the formula [RE(BH4)2(C3H5)(thf) x] (RE=Sc ( 1), x=2; RE=Y ( 2) and La ( 3), x=3) were synthesized by reaction of the corresponding rare-earth trisborohydrides [RE(BH4)3(thf) x] with half an equivalent of bis(allyl)magnesium. The complexes were fully characterized by determining their X-ray structure. Similar to their previously described Nd ( 4) and Sm ( 5) analogues, these complexes display a monomeric structure with two terminal trihapto BH4 groups, one π-η3 allyl ligand, three THF molecules for complexes 2 and 3, and two THF molecules for complex 1. The catalytic behavior of complexes 1- 5 toward the ring-opening polymerization (ROP) of l-lactide ( l-LA) and ϵ-caprolactone (ϵ-CL) was assessed. The Nd complex featured the best activity toward l-LA (turnover frequency (TOF)=1300 h−1) and the order was Nd>La>Sm>Y>Sc. Complexes 1- 3 were found very active for the ROP of ϵ-CL (TOF=166 000 h−1), which is in line with the already established exceptionnally high performance of complexes 4 and 5. With both monomers, it was shown that the borohydride moiety was the preferentially initiating group, rather than the allyl one. The random copolymerization of l-LA and ϵ-CL was performed with complexes 1- 5, in the absence or in the presence of benzyl alcohol as a chain-transfer agent, affording copolymers with ϵ-caprolactone up to 62 % inserted. The copolymers synthesized display a variety of microstructures, that is, blocky, random, or quasi-alternating. [ABSTRACT FROM AUTHOR]

In the present study, we report the first silver-dependent enantiodivergent gold-catalysed reaction. The asymmetric intramolecular hydroamination of alkenes catalysed by the combination of a single chiral binuclear gold(I) chloride complex and silver perchlorate can afford both enantiomers of the products by a simple solvent change from toluene to methanol. Such an enantiodivergent reaction is strictly independent of the reaction temperature or of the nature of the catalyst anion and displays the same first-order kinetic rate law with respect to substrate concentration in both solvents. Beyond a simple solvent effect the enantioinversion is controlled by gold-silver chloride adducts which occur only in methanol and allow a dual activation of the reagent. While one single gold atom activates the alkene moiety, the other gold atom forms an oxophilic gold-silver chloride adduct which is likely to interact with the carbamate function. By comparison with toluene, which affords ( S)-enantiomer, this proximal and bimetallic activation would allow an opposite stereodifferentiation of the two diastereomeric intermediates during the final protodeauration step and lead therefore to the ( R)-enantiomer. [ABSTRACT FROM AUTHOR]

The catalytic acceptorless dehydrogenative oxidation of biosourced alcohols into carboxylic acid salts was achieved using earth-abundant Fe and Mn complexes that feature aliphatic PNP pincer ligands in good to excellent yields. The Fe derivatives were characterized by using 57Fe NMR spectroscopy. Mn pincer catalysts are catalytically more efficient than their Fe counterparts thanks to their robustness under basic conditions. Attempts to generate aldehydes from alcohols were not successful using the Fe and Mn species, but a commercially available Ru analogue achieves this transformation selectively under very mild conditions in the presence of a large excess of acetone as a hydrogen acceptor. [ABSTRACT FROM AUTHOR]

Readily accessible cationic IrIII metallacycles catalyze efficiently the chemoselective hydrosilylation of tertiary and secondary amides to amines. The catalyst described herein operates at low loadings using inexpensive 1,1,3,3-tetramethyldisiloxane and allows fast reactions with high yields, selectivities, and turnover numbers. A transient iminium intermediate has been observed for the first time by using mass spectrometry, and the activation of the catalyst and the silane reagent have been studied by using DFT calculations. These fundamental insights support the present and future improvements of IrIII metallacycles through proper ligand modifications and enable further broad applications of catalysts based on metallacycles. [ABSTRACT FROM AUTHOR]

The combination of an iridium(III) metallacycle and 1,3,5-trimethoxybenzene catalyses rapidly and selectively the reduction of esters to aldehydes at room temperature with high yields through hydrosilylation followed by hydrolysis. The ester reduction involves the trapping of transient silyl cations by the 1,3,5-trimethoxybenzene co-catalyst, supposedly by formation of an arenium intermediate whose role was addressed by DFT calculations. [ABSTRACT FROM AUTHOR]

The catalytic conversion of alcohols into carboxylic acid salts in water was performed in the presence of ruthenium complexes supported by aliphatic PNP pincer ligands preformed or formed in situ. High activity toward a wide substrate scope was achieved with turnover number values of up to 4000. The air-stable catalytic system can be recycled by using toluene as a catalyst-immobilizing phase; the activity is maintained after five consecutive runs. Finally, mechanistic studies allowed some fundamental aspects related to water activation to be unveiled and to the mechanism postulated. [ABSTRACT FROM AUTHOR]

A selected diphosphine binuclear gold(I) chloride complex was combined with a silver salt to catalyze efficiently, for the first time, the asymmetric intramolecular hydroamination of alkenes with high conversions and enantioselectivities, in mild conditions and in presence of water. Both enantiomers of the products could be obtained by controlling the molecular ion-pairs through the solvent polarity. The gold(I) cationic active species was characterized unambiguously at the solid state by X-ray analysis and in solution by DOSY 1H NMR experiments. No contribution of silver chloride was observed on the bonding mode of the catalyst. [ABSTRACT FROM AUTHOR]

Copper sulfides and copper selenides have recently been reported as new and promising low-cost and environmentally friendly thermoelectric materials. Here, it is shown that these materials have actually been studied for more than 190 years and the absence of commercial thermoelectric modules based on them stems from some major intrinsic issues related to these chalcogenides. Further development of these semiconductors will require addressing and solving these problems before large scale utilization can be considered. [ABSTRACT FROM AUTHOR]

The preparation of optically active lactams from 3-aryl-2-piperidinone is reported. The quaternary carbon stereocentres were formed using palladium-catalysed asymmetric allylic alkylation reactions. The resulting enantioenriched compounds are useful intermediates for the synthesis and development of neurokinin antagonists. [ABSTRACT FROM AUTHOR]

A set of O-alkylated or O-arylated β-iodo ethers has been synthesized from isosorbide. Isosorbide is a competitive starting material for various valuable derivatives by functionalization and/or substitution since it is a renewable and carbon neutral material that is produced on an industrial scale from sorbitol. The key step was the iodoetherification of isosorbide-derived glycals with a variety of oxygenated nucleophiles in the presence of N-iodosuccinimide. trans-Iodo ethers and acetate were obtained in good yields and the removal of iodide affords isosorbide derivatives. The usefulness of this new approach is illustrated by the synthesis of a surfactant having a dimer of isosorbide as hydrophilic group and by the preparation of a structurally unusual bicyclic anhydro carbohydrate. [ABSTRACT FROM AUTHOR]

The 3,5-diacetyl-4-methylpyrazole diketone has been synthesized and its crystal structure has been determined. This diketone reacts with hydroxylamine hydrochloride to give the dioxime derivative. This reaction, conducted in presence of copper II ions, leads to the formation of L2M2 copper II complexes. J. Heterocyclic Chem., (2010). [ABSTRACT FROM AUTHOR]

The high-temperature phase I of anhydrous caffeine was obtained by heating and annealing the purified commercial form II at 450 K. This phase I can be maintained at low temperature in a metastable state. A powder X-ray diffraction pattern was recorded at 278 K with a laboratory diffractometer equipped with an INEL curved position-sensitive detector CPS120. Phase I is dynamically orientationally disordered (the so-called plastic phase). The Rietveld refinements were achieved with rigid-body constraints. It was assumed that on each site, a molecule can adopt three preferential orientations with equal occupation probability. Under a deep undercooling of phase I, below 250 K, the metastable state enters in a glassy crystal state. [ABSTRACT FROM AUTHOR]

Such rare‐earth (RE) complexes (RE=La, Nd, Sm, Y, Sc) contain allyl and borohydride groups that are both potential initiators towards the ring‐opening polymerization of cyclic esters. They display high activity towards homo‐ and co‐polymerization of l‐LA and ϵ‐CL, producing a wide range of copolymers. The borohydride moiety is shown to preferentially initiate the polymerization. For more information see the Full Paper by F. Bonnet, M. Visseaux et al. on page 15644 ff. [ABSTRACT FROM AUTHOR]

In the background is featured Ginkakuji (Silver Pavilion), a Zen temple along Kyoto′s eastern mountains (Higashiyama) in Japan. In the foreground is featured a chemistry sketch based on the Yin and Yang symbol. As many possible dualities (such as light and dark, fire and water…) are thought of as physical manifestations of the duality symbolised by Yin and Yang, parallels can be drawn with organic chemistry and the gold(I)‐catalysed asymmetric hydroamination of alkenes. An enantiodivergent reaction is possible depending on the presence of silver. Whereas a gold‐catalysed hydroamination reaction afforded (S)‐product in toluene, the use of methanol led to an enantioinversion and the generation of (R)‐product through solvation of silver and bimetallic activation of the amino‐alkene reagent. For more information see the Full Paper by F. Agbossou‐Niedercorn, C. Michon and co‐workers on page 10777 ff. [ABSTRACT FROM AUTHOR]

The Cover picture shows how ruthenium pincer complexes catalyze the oxidation of alcohols into carboxylic acids in water, which acts as the oxygen source while H2 is released as the only by‐product, as illustrated by the bubbles. More details can be found in the Full Paper by Zhang et al. on page 1413 in Issue 12, 2016 (DOI: 10.1002/cssc.201600243). [ABSTRACT FROM AUTHOR]

In the title compound, C17H16N2O, the fused benzimidazol-2(3H)-one system is essentially planar, the largest deviation from the mean plane being 0.006 (2) Å for the carbonyl C atom. Its mean plane is almost perpendicular to the benzyl plane and to the allyl group, making dihedral angles of 80.6 (1) and 77.4 (3)°, respectively. The benzyl group and the allyl subsituent lie on opposite sides of the fused ring system. In the crystal, mol-ecules are linked by bifurcated C-H⋯O hydrogen bonds in which the carbonyl O atom acts as accepter to two aromatic C-H groups, forming a two-dimensional network parallel to (001).

In the title compound, C24H18ClN3O2, the benzimidazole plane is nearly perpendicular to the phenyl ring and to the isoxazole ring, making dihedral angles of 75.95 (7) and 73.04 (8)°, respectively, but the two residues point in opposite directions with respect to the benzimidazole plane. The dihedral angle between the chloro-phenyl and isoxazole rings is 7.95 (8)°. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds into inversion dimers.

In the title compound, C14H16BrN3O5, the N atoms adjacent to the carbonyl group in the five-membered ring are substituted by (1,3-dioxolan-2-yl)methyl groups. The fused ring system is essentially planar, with the largest deviation from the mean plane being 0.014 (2) Å for the C atom bearing the Br atom. The first oxolane ring, attached on the side of the N atom belonging to the pyridine ring, has an envelope conformation with one of the O atoms as the flap, whereas the second oxolane ring displays a twisted boat conformation. The two oxolane rings display envelope and twisted boat conformations. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, building chains parallel to the a-axis direction.

The fused imidazole and pyridine rings in the title compound, C13H10BrN3O, are linked to a benzyl group. The fused ring system is essentially planar, the largest deviation from the mean plane being 0.006 (2) Å. The phenyl ring is not coplanar with the fused ring system, as indicated by the dihedral angle of 67.04 (12)°. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers.

The fused five- and three six-membered rings of the anthra[1,2-d]imidazole-trione part of the title compound, C27H20N4O4, show two different substituents at the imidazole N atoms, viz. an allyl group and a [3-(pyridin-4-yl)-4,5-di-hydro-isoxazol-5-yl]methyl group. The fused-ring system is approximately planar [r.m.s. deviation = 0.232 (2) Å], but is slightly buckled along the common edge of the two pairs of adjacent rings, with a dihedral angle between them of 11.17 (6)°. The isoxazole ring makes dihedral angles of 27.2 (2) and 12.7 (2)° with the imidazole and pyridine rings, respectively. Weak C-H⋯O and C-H⋯N hydrogen bonds ensure the cohesion of the crystal structure, forming a three-dimensional network.

In the title compound, C21H12N2O3, the fused-ring system is roughly planar, the largest deviation from the mean plane being 0.084 (2) Å. The two prop-2-yn-1-yl groups are almost perpendicular to the fused ring plane, making C-C-N-C torsion angles of -103.4 (2) and -105.3 (2)°, and point in opposite directions with respect to the plane. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming a three-dimensional network.

The title compound, C(23)H(20)N(2)O(7), consists of three fused six-membered rings (A, B and C) and one five-membered ring (D), linked to two ethyl acetate groups. The four fused rings are slightly folded around the O=C⋯C=O direction of the anthraquinone system, with a dihedral angle of 3.07 (8)° between the fused five- and six-membered rings (C and D) and the terminal ring (A). The planes through the atoms forming each acetate group are nearly perpendicular to the mean plane of the anthra[1,2-d]imidazole system, as indicated by the dihedral angles between them of 79.94 (9) and 85.90 (9)°. The crystal packing displays non-classical C-H⋯O hydrogen bonds.

The title compound, C(37)H(24)N(2)O(3), is a 1H-anthra[2,1-d]imidazole-2,6,11(3H)-trione derivative having naphthyl-methyl substitutents attached to the imidazole N atoms. The anthraquinone part of the mol-ecule is somewhat folded along the the line connecting the carbonyl bonds. The dihedral angle between the two benzene rings is 7.8 (1)°. The two naphthyl systems of the substituents of the imidazole ring are positioned on the same side of the five-membered ring; these are approximately coplanar, the dihedral angle between the napthyl systems being 4.3 (2)°.

The title compound, C(37)H(26)N(4)O(7), is a 1H-anthra[2,1-d]imidazole-2,6,11(3H)-trione derivative having isoindolindionylpropyl substitutents attached to the imidazole N atoms. The anthraquinone fragment is buckled, the dihedral angle between the two benzene rings being 1.6 (1)°. The two isoindoline rings of the substituents of the imidazole ring are positioned on opposite sides of the five-membered ring; these are nearly mutually perpendicular [dihedral angle between isoindoline rings = 88.3 (1)°].

The bidentate 1,3,4-thia-diazole ligand, namely, 2,5-bis-(2-pyrid-yl)-1,3,4-thia-diazole (denoted L), untested as a polydentate ligand, has been found to form the monomeric title complex, [Ni(C(12)H(8)N(4)S)(2)(H(2)O)(2)](BF(4))(2). The complex shows an octa-hedral environment of the nickel cation in which the Ni(2+) ion is located on a center of symmetry, linked to two ligands and two water molecules. In this 1:2 complex (one metal for two organic ligands) each thia-diazole ligand uses one pyridyl and one thia-diazole N atom for chelate binding. In the second pyridyl substituent, the N atom is oriented towards the same direction as the S atom of the 1,3,4-thiadiazole ring. The mean plane of the thia-diazole and pyridyl rings linked to the nickel cation forms a dihedral angle with the other pyridine ring of 18.63 (8)°. The tetra-fluorido-borate ions can be regarded as free anions in the crystal lattice. Nevertheless, they are involved in an infinite two-dimensional network parallel to ([Formula: see text]01) through O-H⋯F hydrogen bonds.

The mol-ecular structure of the title compound, C(28)H(20)N(4)O(6), consists of three fused six-membered rings (A,B,C) and one five-membered ring (D). The latter is linked to an isoxazole ring (E) via a methyl-ene unit. A 4-nitro-phenyl substituent (F) is attached to the isoxazole. The fused five and six-membered rings (C,D) are almost coplanar with an r.m.s. deviation of 0.0345 Å and make a dihedral angle of 9.40 (8)° with ring A. The isoxazole and 4-nitro-phenyl rings (E,F) are also almost coplanar with the imidazole and the fused adjacent ring (C,D), forming a dihedral angle of 11.4 (6)°. The crystal packing displays inter-molecular C-H⋯O hydrogen bonding. An intra-molecular C-H⋯O inter-action also occurs.

The mol-ecule of the title compound, C(29)H(20)N(2)O(3), contains four fused rings, three are six-membered rings and one is the five-membered imidazole ring. The fused-ring system is linked to two benzyl groups. The four fused rings are folded around the O=C⋯C=O direction of the anthraquinone, with a dihedral angle of 16.36 (8)° between the two terminal rings (A and D). The imidazole ring (D) is almost perpendicular to the two benzyl groups (E and F) with dihedral angles of 86.69 (17) and 83.15 (13)°, respectively. In the crystal, adjacent mol-ecules are linked by inter-molecular C-H⋯O hydrogen bonding.

The imidazopyridine ring system in the title compound, C(9)H(8)BrN(3)S, is almost planar [r.m.s. deviation of the C and N atoms = 0.007 (1) Å]. The S and methyl-ene C atoms connected to the five-membered ring lie within this plane. The remaining two methyl-ene groups of the thia-zine ring are disordered over two sets of sites in a 0.817 (5):0.183 (5) ratio.

The title compound, C(7)H(6)BrN(3)O, was obtained from the reaction of 6-bromo-1H-imidazo[4,5-b]pyridin-2(3H)-one with methyl iodide. All non-H atoms lie in a common plane [r.m.s deviation = 0.017 (1) Å]. The amino group is a hydrogen-bond donor to the carbonyl group of an inversion-related mol-ecule, the pair of hydrogen bonds giving rise to a hydrogen-bonded dimer.