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trans-3-Benzyloxycarbonylamino-1-methyl-3-(methylcarbamoyl)azetidine-1-oxide was prepared by stereoselective oxidation of the corresponding azetidine precursor. The stable molecule was characterized in a low-polarity solution by IR, 1H-NMR and 13C-NMR, and in the solid state as a co-crystal with water by X-Ray diffraction. The N-oxide function made a strong intramolecular 7-membered ring hydrogen bond with the methyl amide NH in solution and formed an intermolecular H-bond with the carbamate NH in a neighboring molecule in the solid state. [ABSTRACT FROM AUTHOR]

A broadly applicable diastereo‐ and enantioselective inverse‐electron‐demand Diels–Alder reaction of 2‐pyrones and acyclic enol ethers is reported herein. Using a copper(II)‐BOX catalytic system, bridged bicyclic lactones are obtained in very high yields (up to 99 % yield) and enantioselectivities (up to 99 % ee) from diversely substituted 2‐pyrones and acyclic enol ethers. Mechanistic experiments as well as DFT calculations indicate the occurrence of a stepwise mechanism. The synthetic potential of the bridged bicyclic lactones is showcased by the enantioselective synthesis of polyfunctional cyclohexenes and cyclohexadienes, as well as a carbasugar unit. [ABSTRACT FROM AUTHOR]

A broadly applicable diastereo‐ and enantioselective inverse‐electron‐demand Diels–Alder reaction of 2‐pyrones and acyclic enol ethers is reported herein. Using a copper(II)‐BOX catalytic system, bridged bicyclic lactones are obtained in very high yields (up to 99 % yield) and enantioselectivities (up to 99 % ee) from diversely substituted 2‐pyrones and acyclic enol ethers. Mechanistic experiments as well as DFT calculations indicate the occurrence of a stepwise mechanism. The synthetic potential of the bridged bicyclic lactones is showcased by the enantioselective synthesis of polyfunctional cyclohexenes and cyclohexadienes, as well as a carbasugar unit. [ABSTRACT FROM AUTHOR]

We describe here an asymmetric aldol reaction based on the principle of Memory of Chirality. From α‐amino acids such as leucine and methionine, we have synthesized in two steps quaternary α‐amino acid derivatives with high diastereoselectivity and enantioselectivity, using the chirality of the initial α‐amino acid as the only chirality source. Furthermore, we were able to determine the relative and absolute configurations of the aldol products thanks to crystallographic structures and thus showed that the relative configuration depended on the aldehyde employed. We proposed a stereoselectivity explanation and obtained also quaternary β‐hydroxy α‐amino acids after acidic hydrolysis. [ABSTRACT FROM AUTHOR]

A catalytic enantioselective vinylogous domino reaction has been achieved from ketone‐derived benzylidene Meldrum's acid and α‐ketolactones to provide spirolactone dihydropyranones with more than 99% ee. An Auto Tandem Catalysis (ATC) process resulting from dual and complementary role of (DHQ)2PHAL organocatalyst resulted in a sequence involving an asymmetric vinylogous formal (4+2) cycloaddition of benzylidene and the subsequent kinetic resolution operating through a 1,3‐prototropic shift leading to good yields (>50%) and the high selectivity. [ABSTRACT FROM AUTHOR]

New mononuclear non‐heme FeII complexes derived from a well‐known pentadentate amine/pyridine ligand were synthesized. The new ligand bears an additional OH group on one pyridyl aimed at developing second sphere hydrogen bonds. Two binding modes of the ligand were observed that can be selectively obtained through the choice of the counterion: the OH group develops an intramolecular H‐bond with the 6th exogenous ligand in the classical mode, or an intermolecular one with the unbound triflate counterion in the alternative mode. The complexes were studied by cyclic voltammetry in the reductive activation of O2. The addition of an H‐bond improves the O2 activation potential with a gain of 90 mV in the classical case and 220 mV in the alternative one. The difference is ascribed to the development of stabilizing H‐bonds within the FeIII‐peroxo intermediate with the proximal O atom of peroxo (classical mode) or the distal one (alternative mode). Ultimately, the complex in the alternative mode activates O2 at −0.5 V vs SCE (500 mV gain compared to free O2). We took advantage of this significantly reduced energetic cost to carry out and achieve the electroassisted oxidation of thioanisole by O2 at −0.5 V vs SCE. [ABSTRACT FROM AUTHOR]

Two new symmetrical and unsymmetrical diiron(III) complexes were synthesized and characterized by X-ray diffraction analysis, mass spectrometry, UV-visible and Mössbauer spectroscopies. They proved to be good catalysts for alkene and alkane oxidation reactions by H2O2 in acetonitrile solution, and interesting effects of both the nature and the symmetry of the complexes were observed on catalysis in the presence of water. [ABSTRACT FROM AUTHOR]

We describe a simple and sustainable MgBr2‐mediated electrochemical dearomative dihydroxylation and hydroxycyclization reactions of indoles with water. MgBr2 is used in substoichiometric amount and acts as an electrolyte and potentially as a redox mediator to indirectly oxidize the indole nucleus into a bromonium ion which is involved in the aforementioned reactions. [ABSTRACT FROM AUTHOR]

Herein, we report the preparation of bridged tetrahydrobenzo[b]azepines, which was accomplished through an aza‐Piancatelli cyclization/Michael addition sequence in a one‐pot fashion from readily available precursors. It is noteworthy that a general method to access these scaffolds was hitherto unprecedented. Additionally, the multifaceted aspects of this process have been exemplified through its application to the synthesis of 2‐azabicyclo[3.2.1]octanes and bridged tetrahydrobenzo[b]oxepines, along with post‐derivatizations. [ABSTRACT FROM AUTHOR]

Herein, we report the preparation of bridged tetrahydrobenzo[b]azepines, which was accomplished through an aza‐Piancatelli cyclization/Michael addition sequence in a one‐pot fashion from readily available precursors. It is noteworthy that a general method to access these scaffolds was hitherto unprecedented. Additionally, the multifaceted aspects of this process have been exemplified through its application to the synthesis of 2‐azabicyclo[3.2.1]octanes and bridged tetrahydrobenzo[b]oxepines, along with post‐derivatizations. [ABSTRACT FROM AUTHOR]

The synthesis and solid‐state characterization of an array of well‐defined low‐coordinate C1‐symmetric β‐diketiminatoiron(II) alkyl complexes B3–B6 featuring steric and electronic variations on one of the N‐aryl substituents of the β‐diketiminate ligand scaffold are reported. All complexes display unique catalytic abilities of promoting the selective exo‐cyclohydroamination of unprotected 2,2‐diphenylpent‐4‐en‐1‐amine (1 a) under mild reactions conditions. The incorporation of a potentially coordinative ortho‐methoxy substituent on one of the N‐aryl rings of the β‐diketiminate skeleton, in conjunction with a more crowded 2,6‐diisopropylphenyl group on the other, affords a far more active catalyst (B3) than our previously reported C2‐symmetric β‐diketiminatoiron(II) alkyl complex B (Ar1=Ar2=2,4,6‐(Me)3C6H2)/cyclopentylamine system. Comparative studies let us postulate that this superior activity of B3, when compared with B4‐B6, is likely arising from steric effects and/or the coordinating ability of the ortho‐methoxy substituent. The scope and limitations of this novel C1‐symmetric β‐diketiminatoiron(II) alkyl complex B3 are also presented. [ABSTRACT FROM AUTHOR]

We report our efforts to apply an N-iodosuccinimide-mediated dearomative oxidative coupling of indoles and phenols to benzofuroindoline- containing polycyclic scaffolds related to the natural product bipleiophylline. Suitable conditions from N-substituted indoles are developed and applied to the synthesis of a hexacyclic model starting from a tetracyclic ABCE precursor. [ABSTRACT FROM AUTHOR]

A diphenyl-boron β-diketonate complex was synthesized. Its photophysical properties were studied in solution and in the solid-state, and compared to those of its parent diketone and the corresponding difluoro-boron complex. TD-DFT calculations show that the molecular orbitals involved in the first Franck–Condon transition are very different for the three compounds studied. The difluoro-boron complex is strongly fluorescent in solution, and remains fluorescent in the solid-state. The free diketone turns to be very weakly fluorescent in solution and displays significant Aggregation Induced Enhanced Emission (AIEE) in the crystalline state, which can be explained by a rigidification of the molecule, while the diphenyl-boron complex is weakly fluorescent in solution as well as in the solid-state. For the free diketone and the difluoro-boron complex a mechanofluorochromic response is observed upon grinding the crystalline powder in a mortar, while for the diphenyl-boron complex no fluorescence emission change is detected under these conditions. Overall, this study shows that the nature of the chelating group has a crucial influence on the photophysical and mechanofluorochromic properties of β-diketonate complexes, leading to a wide variety of behaviors within the closely related structures of such derivatives. [ABSTRACT FROM AUTHOR]

• The gas-phase structure of a cyclic dipeptide is determined by laser spectroscopy. • Cyclo Tyr-Phe-exists in two geometries, with one ring folded and the other extended. • Minor structural differences happen depending on the chirality of the residues. • The solid-state structure is studied by vibrational circular dichroism. • Dimers involving a double hydrogen bond account for the solid-state results. The structures of the diastereomer diketopiperazine dipeptides cyclo(LTyr-LPhe) and cyclo-(DTyr-LPhe) are studied in the gas phase using resonance-enhanced two-photon ionization, IR/UV double resonance spectroscopy and quantum chemical calculation. Both diastereomers exhibit two conformations, with the tyrosine ring folded over the DKP ring and the phenylalanine ring extended outwards, or vice versa. The two diastereomers differ only slightly by the nature of weak CH···π and NH···π interactions. The crystal structure of cyclo(LTyr-LPhe) is determined by X-ray crystallography and is composed of monomers with folded tyrosine ring. The vibrational circular dichroism spectrum is interpreted by the existence of dimers in the solid state. Quantum chemical calculation shed light on the structural modifications between the gas phase and the solid state. [Display omitted] [ABSTRACT FROM AUTHOR]

We report the access to the benzofuro[3,2-b]indoline framework of phalarine from benzofuran-2-ones via the Fischer indolization reaction which was interrupted at the deamination step. Unexpectedly, allyl nucleophiles did not add to the aminal position of these benzofuro[3,2-b]indoline amines but to the adjacent ring junction center in the presence of trifluoroborane to deliver 3,3-disubstituted indolines containing a difluoroboron-containing six-membered ring with fluorescence properties. [ABSTRACT FROM AUTHOR]

We report the cyclization of 3-substituted N-acetylindoles for the straightforward synthesis of 3,3-spiroindolines via the Friedel-Crafts reaction of an appended aryl group or the formal [2 + 2] cycloaddition of an appended alkene. Our strategy involves an Umpolung of the C2=C3 bond of the indole nucleus during FeCl3-mediated hydroarylation or annulation reactions. [ABSTRACT FROM AUTHOR]

We report the Friedel-Crafts coupling of a tyrosine unit with tryptophan-derived pyrrolindolenium ions which are configurationally stable. The reaction allowed the stereoselective and divergent access to the required quaternary stereocenters found in diazonamide A and azonazine at the junction of the tyrosine and tryptophan units. [ABSTRACT FROM AUTHOR]

By reacting IPr ⋅InBr3 with AgSbF6 in dichloroethane at room temperature, we could obtain single crystals comprising [{(IPr ⋅InBr3)(Ag ⋅(CH2Cl)2)}2][SbF6]2 ( 1) and two identical HSbF6 units. It is presumed that the reaction gave rise to [IPr ⋅InBr3− x][SbF6] x ( x=1, 2, or 3) which reacted with adventitious water to give HSbF6 and [IPr ⋅InBr3− x(OH)][SbF6] x−1. The experiment was reproduced at 60 °C, eventually leading to the indium hydroxide [{IPr ⋅In(OH)0.5(H2O)4.5}2][SbF6]5 ( 2). [ABSTRACT FROM AUTHOR]

We present the study of nano- and microparticles of the Fe(Me2-bpy)2(NCSe)2 spin-crossover complex prepared from the diamagnetic precursor [Fe(Me2-bpy)3](NCSe)2·S. Two solvates of the latter were characterized by single-crystal X-ray structures at 100 K (S = 2MeOH or 3H2O). The extraction of one Me2-bpy per metal ion in [Fe(Me2-bpy)3](NCSe)2·S was achieved either by thermolysis at temperature higher than 150 °C or by precipitation in an anti-solvent, leading to a polycrystalline or particulate powder of Fe(Me2-bpy)2(NCSe)2. This chemical conversion was investigated by TGA, powder X-ray diffraction, IR, Raman and magnetic measurements. The S = 0 ↑S = 2 spin-crossover of Fe(Me2-bpy)2(NCSe)2 centered at ca. 340 K is almost complete at low temperature (HS residue ≤ 5% below 250 K) while at 370 K, the HS fraction can be estimated at ∼0.7. These features are essentially preserved whatever be the size of particles (56, 460 and 1200 nm) as a consequence of the weak cooperativity of the process occurring at high temperature, the crystallinity and the molecular nature of particles. This approach leading to dispersion of small particles in a polymer is suitable for the preparation of materials of optical quality, via the stabilization and processing of nanoparticles in convenient matrices to form thin films. [ABSTRACT FROM AUTHOR]

Using a β,γ-diamino acid, several small hybrid α/γ peptides have been synthesized and their conformations investigated through extensive NMR studies and molecular dynamics. A tripeptide and a tetrapeptide have thus shown several hydrogen bonds in solution, including a 13-membered ring involving the β-nitrogen. [ABSTRACT FROM AUTHOR]

Inspired by the biogenetic synthesis of benzofuroindoline-containing natural products, we designed an oxidative coupling between phenol and N-acetyl indoles. This straightforward and direct radical process, mediated by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and FeCl3 allowed the regioselective synthesis of benzofuro[3,2-b]indolines, whose structure is found in the natural product phalarine. [ABSTRACT FROM AUTHOR]

Inspired by the biogenetic synthesis of benzofuroindoline-containing natural products, we designed an oxidative coupling between phenol and N-acetyl indoles. This straightforward and direct radical process, mediated by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and FeCl3 allowed the regioselective synthesis of benzofuro[3,2-b]indolines, whose structure is found in the natural product phalarine. [ABSTRACT FROM AUTHOR]

Solid‐State Vibrational Circular Dichroism (VCD) can be used to determine the absolute structure of chiral crystals, but its interpretation remains a challenge in modern spectroscopy. In this work, we investigate the effect of a twofold screw axis on the solid‐state VCD spectrum in a combined experimental and theoretical analysis of P21 crystals of (S)‐(+)‐1‐indanol. Even though the space group is achiral, a single proper symmetry operation has an important impact on the VCD spectrum, which reflects the supramolecular chirality of the crystal. Distinguishing between contributions originating from molecular chirality and from chiral crystal packing, we find that while IR absorption hardly depends on the symmetry of the space group, the situation is different for VCD, where completely new non‐local patterns emerge. Understanding the two underlying mechanisms, namely gauge transport and direct coupling, will help to use VCD to distinguish polymorphic forms. [ABSTRACT FROM AUTHOR]

Solid‐State Vibrational Circular Dichroism (VCD) can be used to determine the absolute structure of chiral crystals, but its interpretation remains a challenge in modern spectroscopy. In this work, we investigate the effect of a twofold screw axis on the solid‐state VCD spectrum in a combined experimental and theoretical analysis of P21 crystals of (S)‐(+)‐1‐indanol. Even though the space group is achiral, a single proper symmetry operation has an important impact on the VCD spectrum, which reflects the supramolecular chirality of the crystal. Distinguishing between contributions originating from molecular chirality and from chiral crystal packing, we find that while IR absorption hardly depends on the symmetry of the space group, the situation is different for VCD, where completely new non‐local patterns emerge. Understanding the two underlying mechanisms, namely gauge transport and direct coupling, will help to use VCD to distinguish polymorphic forms. [ABSTRACT FROM AUTHOR]

A method for the direct and rare umpolung of the 3 position of indoles is reported. The activation of N-acetylindole with iron(III) chloride allows the CH addition of aromatic and heteroaromatic substrates to the C2C3 double bond of the indole nucleus to generate a quaternary center at C3 and leads regioselectively to 3-arylindolines. Optimization, scope (50 examples), practicability (gram scale, air atmosphere, room temperature), and mechanistic insights of this process are presented. Synthetic transformations of the indoline products into drug-like compounds are also described. [ABSTRACT FROM AUTHOR]

A chiral 1-isopropenyl-1-(3-oxopropyl)disilane derivative undergoes a type II ene reaction under Lewis acid catalyzed conditions to afford the silacyclic compound and an unexpected rearranged product with high diastereoselectivities. This rearrangement occurs through 1,2-migration of a trimethylsilyl group. A common intermediate was proposed to explain the formation of both products. [ABSTRACT FROM AUTHOR]

A series of 5,11,17-triazatrinaphthylene (TrisK) derivatives, large disk-like π-conjugated molecules with C3 h symmetry, has been synthesised by following an optimised synthetic pathway. The synthesis was performed by a four-step protocol based on the N-arylation of 1,3,5-tribromobenzene with appropriate anthranilate derivatives. This strategy permits the generation of either chlorinated ( TrisK-Cl-OC n) or non-chlorinated ( TrisK-H-OC n) alkoxy-substituted derivatives (OC nH2 n+1 with n=3, 10, 12 and 16), thus providing additional versatility in the control of the structure-property relationships. The electronic properties of the various TrisK compounds have been characterised in solution by absorption and emission spectroscopies as well as cyclic voltammetry. The crystal structure of 2,8,14-propyloxy-5,11,17-triazatrinaphthylene TrisK-H-OC3 has been determined by X-ray diffraction analysis, which revealed the presence of stabilising weak intermolecular H bonds. Scanning tunnelling microscopy (STM) at the liquid/solid interface has revealed the remarkable 2D self-assembling properties of the TrisK compounds. In particular, it has shown that TrisK-H-OC12 forms three concomitant self-organised 2D phases with different row-packing arrangements. This 2D polymorphism arises from slow ordering due to the presence of three long dodecyloxy chains on the molecular backbone. Individual molecules can be imaged with spectacular intramolecular resolution, thus providing the possibility of correlating the STM features with the calculated charge density distribution. [ABSTRACT FROM AUTHOR]

A family of lanthanide complexes has been synthesized by the subcomponent self-assembly methodology. Molecular architectures, which were stable in solution and under ambient conditions, were designed by the in situ formation of ligands around lanthanide ion templates. Magnetic studies indicated that, despite the low C2 symmetry, 1 and 2 display single molecule magnet (SMM) behavior, with 1 exhibiting an effective energy barrier of the relaxation of the magnetization Ueff/kBa = 50 K and the pre-exponential factor τ0 = 6.80 X 10-7 s. Step-like features in the hysteresis loops indicate the presence of quantum tunneling of the magnetization (QTM). [ABSTRACT FROM AUTHOR]

Abstract: The photophysics of a red-emitting push–pull triarylamine compound (fvin) comprising a triphenylamino electron donor core and a dicyanovinylene electron acceptor group is investigated by steady-state absorption and emission and femtosecond time-resolved absorption spectroscopy in room-temperature n-hexane, toluene, ethanol, and acetonitrile solvents. Fvin is strongly fluorescent in apolar solvents upon excitation of the S0 →S1 intramolecular charge transfer (ICT) transition, but hardly emissive in polar solvents. Time-resolved spectra reveal a strong dependence of the excited-state dynamics on both the solvent polarity and viscosity. Unlike n-hexane solutions where the fluorescent ICT excited state remains weakly solvated and keeps a structure close to that of the Franck–Condon level, significant stabilization of the ICT state operates in toluene, leading to a relaxed fluorescent ICT′ form with stronger charge transfer character. This was featured by a notable dynamic Stokes shift of the stimulated emission (SE) band occurring in 15ps. However the similarly high fluorescence quantum yield and lifetime in n-hexane and toluene excludes any large structural distortion on going from ICT to ICT′. In acetonitrile and ethanol, the SE shift dynamics is enhanced and clearly biphasic. The first step can be ascribed to an ICT→ICT′ conformational relaxation as in toluene. The second step, accompanied by a drastic drop of the SE intensity and a strong evolution of the excited-state absorption spectrum (time-constant 1.5ps in acetonitrile, 9ps in ethanol), corresponds to the appearance of a new ICT″ state with enhanced charge localization and separation, most probably associated with a rotation of the phenyldicyanovinylene group. This large-amplitude distortion is followed by fast internal conversion to the ground state (9ps in acetonitrile, 21ps in ethanol), accounting for the almost nonemissive character of fvin in polar solvents. [Copyright &y& Elsevier]

nder noble (Au, Pt, Ru) and group 13 (Ga, In) metals catalysis, 1,6-arenynes rearrange to give 1,2-dihydronaphthalenes in a high yielding, regiocontrolled fashion. When the reaction is carried out in the presence of electron-rich arenes (anisole, phenol, indole derivatives), Friedel-Crafts addition may follow the cycloisomerization step. Only GaX3 salts proved able to catalyze these two C-C bond formation events. This specificity of gallium has been exploited for the synthesis of valuable polycyclic compounds that would be very difficult to prepare otherwise. For instance, tetrahydroisoquinolines and tetrahydrobenzoazepines have been obtained by selective 6-exo-dig or 7-endo-dig cyclization of N-tethered 1,6-arenynes. DFT calculations were carried out to shed light on the mechanism and provide a rationale for this regiodivergency. Computations also reveal the fundamental role of the tether in the stabilization of carbocationic species. Differential reactivities of other types of substrates in gallium- and gold-catalyzed cascades are also exposed, showing that the two approaches are complementary. In particular, bimolecular Friedel-Crafts additions are facilitated under gallium catalysis. [ABSTRACT FROM AUTHOR]

Abstract: Two new ligands of transition metal cations based on galactose-derived scaffolds were synthesised: 1,5-anhydro-2-deoxy-3,4,6-tri-O-(2-picolyl)-d-galactitol and methyl 2-deoxy-3,4,6-tri-O-(2-picolyl)-α-d-galactopyranoside. These ligands permitted the isolation as single crystals of a Co(II) and a Ni(II) complex, respectively. The structures of both complexes were determined by X-ray crystallography showing a coordination sphere including sugar-bound oxygen atoms. The sugar-derived ligands were found to be in both cases in high energy conformations in the crystal structures of the complexes. These conformations contain an arrangement of sugar-bound oxygen atoms similar to those observed in polyol–metal and carbohydrate–metal complexes. [Copyright &y& Elsevier]

Abstract: The synthetic route towards a novel tetradentate ligand bearing two amido and imidazole rings is reported. This ligand has been designed to study the relationship between the protonic state of the ligand through the imidazole moieties towards the electronic behaviour of metal complexes. [Copyright &y& Elsevier]

Abstract: The condensation of a series of arylacetonitriles with aldehydes can be carried out by mixing equivalent amounts of reagents with neat powdered KOH at room temperature for 3–60min depending on the aldehyde steric hindrance. At higher temperature (110°C), yields were generally higher and purity increased within very short reaction times (1–5min). With pentamethylphenylacetonitrile, a phase transfer agent was necessary to give a satisfactory yield. [Copyright &y& Elsevier]

Studies the experimental and theoretical charge density of DL-alanyl-methionine. Collection of X-ray diffraction data up to d=0.50 A resolution at 100 Kelvin for DL-alanyl-methionine single crystal using a charge coupled device area detector; Multipolar crystallographic refinement and analysis of the electron density of the molecule.

We report two new FeIII complexes [L1FeIII(H2O)](OTf)2 and [L2FeIII(OTf)], obtained by replacing pyridines by phenolates in a known non‐heme aminopyridine iron complex. While the original, starting aminopyridine [(L52)FeII(MeCN)](PF6) complex is stable in air, the potentials of the new FeIII/II couples decrease to the point that [L2FeII] spontaneously reduces O2 to superoxide. We used it as an O2 activator in an electrochemical setup, as its presence allows to generate superoxide at a much more accessible potential (>500 mV gain). Our aim was to achieve substrate oxidation via the reductive activation of O2. While L2FeIII(OTf) proved to be a good O2 activator but a poor oxidation system, its association with another complex (TPEN)FeII(PF6)2 generates a complementary tandem couple for electro‐assisted oxidation of substrates, working at a very accessible potential: upon reduction, L2FeIII(OTf) activates O2 to superoxide and transfers it to (TPEN)FeII(PF6)2 leading in fine to the oxidation of thioanisole. [ABSTRACT FROM AUTHOR]

A pair of novel C3-epimeric sugar-derived ligands (glycoligands) with a neutral N40 donor set was synthesized. Copper(ll) complexes of both ligands were obtained and characterized by X-ray crystallography. Cyclic voltammetry, electron paramagnetic resonance, and UV-vis spectroscopies showed similar electronic properties. Mirror-image CD spectra were obtained for the Cu" d-d band, indicating an enantiomeric character of the coordination sphere, which has been rationalized structurally. This example shows the possible predetermination of stereochemistry for complexes by ligands based on a glycoscaffold. [ABSTRACT FROM AUTHOR]

Abstract: Azabicyclo[3.1.0]hexane-1-ols, easily obtained by Ti(IV)-mediated cyclopropanation of amino acid derivatives, constitute versatile, and unprecedented intermediates for the asymmetric synthesis of pharmacologically active products. Indeed, through selective rearrangement, these compounds undergo unusual ring cleavage to lead to pyrrolidinones. Fe(III)-promoted ring opening followed by basic dehydrohalogenation furnishes optically active dihydropyridinones, while Ce(IV)-promoted ring opening provides chiral tricyclopiperidinones via a radical process. [Copyright &y& Elsevier]

Abstract: The synthesis of a dissymmetric biscompartmental ligand holding a salophenic and a bisoxamate coordinating cavities is described. The electrochemical behaviour and X-ray crystallographic data of the dinuclear nickel(II) complex are reported. [Copyright &y& Elsevier]

In the context of bioinspired OAT catalysis, we developed a tetradentate dipyrrinpyridine ligand, a hybrid of hemic and non-hemic models. The catalytic activity of the iron(III) derivative was investigated in the presence of iodosylbenzene. Unexpectedly, MS, EPR, Mössbauer, UV-visible and FTIR spectroscopic signatures supported by DFT calculations provide convincing evidence for the involvement of a relevant FeIII–O–NPy active intermediate. [ABSTRACT FROM AUTHOR]

Three new amine/pyridine FeII complexes bearing pentadentate ligand with one, two or three electron enriched 4‐methoxy‐3,5‐dimethylpyridine were used as catalysts for the oxidation of small organic molecules by hydrogen peroxide. The distribution of products formed suggests that these ligands are not enough electron donating to promote the O−O heterolytic cleavage of the oxidant in order to generate selective FeV(O) species. Using acetic acid in the reaction mixtures results in a significant increase of the efficiency of these catalytic systems. Our investigations show that the use of AcOH leads to the protonation/dissociation of a pyridyl moiety and the formation of (N4)FeII(OAc)(OH) species. These complexes readily react with excess hydrogen peroxide to yield (N4)FeIII(OAc)(OOH) intermediates. These latter intermediates are proposed to evolve into (N4)FeIV(OAc)(O), which are more efficient than the usual (N4)FeIV(O) and (N5)FeIV(O). [ABSTRACT FROM AUTHOR]

We describe here a new process for the synthesis of very high quality 2D Covalent Organic Frameworks (COFs), such a C2N and CN carbon nitrides. This process relies on the use of a metallic surface as both a reagent and a support for the coupling of small halogenated building blocks. The conditions of the assembly reaction are chosen so as to leave the inorganic salts by-products on the surface, to further confine the assembly reaction on the surface and increase the quality of the 2D layers. We found that under these conditions, the process directly returns few layers material. The structure/quality of these materials is demonstrated by extensive cross-characterizations at different scales, combining optical microscopy, Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). The availability of such very large, high-quality layers of these materials opens interesting perspectives, for example in photochemistry and electronics (intrinsic transport properties, high gap substrate for graphene, etc...). [ABSTRACT FROM AUTHOR]

For the first time, azaoxyallyl cations were used as cycloaddition partners with tropone derivatives to access nitrogen-containing [7,6]-fused bicycles in a metal-free process under mild reaction conditions. DFT computations have been used to shed light on the selectivities observed during the course of the reaction. [ABSTRACT FROM AUTHOR]

We report an efficient and environmentally friendly electrochemical approach to perform the bromo cyclization of tryptophol, tryptamine and tryptophan derivatives. The 3a-bromofuranoindolines and 3a-bromopyrroloindolines obtained are of interest in the total synthesis of natural products. This dearomative procedure relies on the generation of an electrophilic bromine reagent by the electrochemical oxidation of MgBr2. No organic byproducts are generated with this protocol which avoids the use of an additional electrolyte. [ABSTRACT FROM AUTHOR]

Peptide models built from cis‐ and trans‐2‐aminocyclobutane‐1‐carboxylic acids (ACBCs) are studied in the solid phase by combining Fourier‐transform infrared spectroscopy (FTIR) absorption spectroscopy, vibrational circular dichroism (VCD), and quantum chemical calculations using density functional theory (DFT). The studied systems are N‐tert‐butyloxycarbonyl (Boc) derivatives of 2‐aminocyclobutanecarboxylic acid (ACBC) benzylamides, namely Boc−(cis‐ACBC)−NH−Bn and Boc−(trans‐ACBC)−NH−Bn. These two diastereomers show very different VCD signatures and intensities, which of the trans‐ACBC derivative being one order of magnitude larger in the region of the ν (CO) stretch. The spectral signature of the cis‐ACBC derivative is satisfactorily reproduced by that of the monomer extracted from the solid‐state geometry of related ACBC derivatives, which shows that no long‐range effects are implicated for this system. In terms of hydrogen bonds, the geometry of this monomer is intermediate between the C6 and C8 structures (exhibiting a 6‐ or 8‐membered cyclic NH⋯O hydrogen bond) previously evidenced in the gas phase. The benzyl group must be in an extended geometry to reproduce satisfactorily the shape of the VCD spectrum in the ν (CO) range, which qualifies VCD as a potential probe of dispersion interaction. In contrast, reproducing the IR and VCD spectrum of the trans‐ACBC derivative requires clusters larger than four units, exhibiting strong intermolecular H‐bonding patterns. A qualitative agreement is obtained for a tetramer, although the intensity enhancement is not reproduced. These results underline the sensitivity of VCD to the long‐range organisation in the crystal. [ABSTRACT FROM AUTHOR]

We describe here a new process for the synthesis of very high quality 2D Covalent Organic Frameworks (COFs), such a C2N and CN carbon nitrides. This process relies on the use of a metallic surface as both a reagent and a support for the coupling of small halogenated building blocks. The conditions of the assembly reaction are chosen so as to leave the inorganic salts by-products on the surface, to further confine the assembly reaction on the surface and increase the quality of the 2D layers. We found that under these conditions, the process directly returns few layers material. The structure/quality of these materials is demonstrated by extensive cross-characterizations at different scales, combining optical microscopy, Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). The availability of such very large, high-quality layers of these materials opens interesting perspectives, for example in photochemistry and electronics (intrinsic transport properties, high gap substrate for graphene, etc...). [ABSTRACT FROM AUTHOR]

[22][23] In the present case, the principle required the preparation of a set of oligomers of an easy-to-use surrogate amino acid, with transformation of all residues present into Aatc(Me) residues in the final step. Keywords: azetidines; late-stage modification; peptides; reductive amination; protected amino acid; oligomers EN azetidines late-stage modification peptides reductive amination protected amino acid oligomers 1787 1790 4 08/29/23 20230915 NES 230915 Graph In the context of a collaborative interdisciplinary program, we were recently given a particular synthetic challenge. Finally, tetramer B 9 b was deprotected as before without incident, but the resulting tetraamine tetrahydrochloride only provided small amounts (<10%) of tetramer B 4 b when subjected to the same reductive amination conditions as above. [29] While the target molecules in our work implicated Aatc(Me) as the constituent amino acid, we took the opportunity to conduct two related experiments on derivative B 6 b (Scheme 3). [Extracted from the article]

The catalytic properties of an iron complex bearing a pentadentate cross-bridged ligand backbone are reported. With H2O2 as an oxidant, it displays moderate conversions in epoxidation and alkane hydroxylation and satisfactory ones in aromatic hydroxylation. Upon addition of an acid to the reaction medium, a significant enhancement in aromatic and alkene oxidation is observed. Spectroscopic analyses showed that accumulation of the expected FeIII(OOH) intermediate is limited under these conditions, unless an acid is added to the mixture. This is ascribed to the inertness induced by the cross-bridged ligand backbone, which is partly reduced under acidic conditions. [ABSTRACT FROM AUTHOR]