Search

The isomerism of dimethyl 2,2′‐(7,8‐dichloro‐1H‐benzo[b][1,4]diazepine‐2,4‐(3H,5H)diylidene)diacetate (1a) and dimethyl 2,2′‐(7,8‐dichloro‐3‐methyl‐1H‐benzo[b][1,4]diazepine‐2,4‐(3H,5H)diylidene)diacetate (1b) was investigated by 1H, 13C and 15N nuclear magnetic resonance (NMR) spectroscopy. In CDCl3 solution, inversion of the diazepine ring was observed, whereas in (D6)DMSO and (D7)DMF solution, besides the ring inversion, a partial cleavage of one chelate ring appeared connected with (E/Z) isomerization about one of the exocyclic C=C bonds. Gibbs free energies (ΔG) and free activation energies (ΔG≠) were calculated based on B3PW91‐SCRF/ZVP DFT computations. Agreement between NMR data and density functional theory (DFT) computations was found. [ABSTRACT FROM AUTHOR]

The iridium catalyzed transfer vinylation of bio‐based polyols and of other alcohols and phenols with interesting structural motifs was accomplished with vinyl acetate in 2‐MeTHF as a green solvent. The optimized synthetic procedure has as main advantages the use of catalytic instead of stoichiometric amounts of base and high selectivities towards the formation of bis‐vinyl ethers as a result of the suppression of the acetal formation reaction that typically occurs in the vinylation of diols. In addition, the thermodynamically preferred transesterification reaction leading to the acetate esters and bis‐esters was completely suppressed. DFT calculations revealed an iridium‐acetate complex as the active catalytic species and they disclosed the importance of the carbonyl group of vinyl acetate for the formation of a six‐membered cyclic intermediate. [ABSTRACT FROM AUTHOR]

The tautomerism and isomerism of several ethyl 2‐(4‐(perfluoroalkyl)dihydro‐2H‐benzo(naphtho)[b][1,4]diazepin‐2‐ylidene)acetates were investigated by 1H‐, 13C‐, 15N‐ and 19F‐NMR spectroscopy and DFT computations. Depending on the polarity and basicity of the solvent a different behaviour was observed. In CDCl3, (D6)acetone and CD3CN solution two chelate hydrogen bonded tautomers, the enaminoimine and the diaminodiene, were found to exist. In the polar and more basic solvents (D6)DMSO and (D7)DMF two further species, the chelate ring‐opened isomers, were detected. The ratio of the isomers is influenced by the solvents and the substituents at the chelate ring. The chelate enaminoimine is favoured in the less polar chloroform, whereas the chelate diaminodiene predominates with increasing polarity of solvents. The length of the perfluoroalkyl chain and the substituents of the phenyl ring do not influence the isomeric equilibrium as much as the chlorine atom in 4‐position. The structures of the isomers were unambiguously confirmed by one‐ and two‐dimensional techniques (1H,1H‐COSY, 1H,1H‐NOESY (EXSY), 1H,13C‐ and 1H,15N‐chemical shift correlation spectra (HSQC and HMBC)). The observed 15N NMR data are typical for enamines, amides and diazepines and additionally confirm the proposed structures of the four isomers. The time‐dependent course of the equilibration in DMSO solution was followed by recording 1H and 19F spectra. Calculated Gibbs free energies (ΔG) correlate essentially with our experimental findings. [ABSTRACT FROM AUTHOR]

The isomerism of 1,5-benzodiazepin-2-ones 3 containing a perfluorinated side chain was investigated by 1H-, 13C-, 15N- and 19F NMR spectroscopy in different solvents. Compounds 3 exist in CDCl 3 , (D 6)acetone, CD 3 CN and (D 5)pyridine solution as one species, whereas in (D 6)DMSO and (D 7)DMF partial (E / Z) isomerisation about the exocyclic C2=C3 bond occurs resulting in two isomers. Gibbs free energies (ΔG) and Free activation energies (ΔG≠) were calculated based on BP86 and BP86-SCRF DFT computations. Image 1 • Fluorine containing 1,5-Benzodiazepin-2-ones exist in solution as one isomeric form due to an intramolecular hydrogen bond. • In solvents that are both polar and basic a second isomer appears to a certain amount. • The new isomer is formed by breaking off the hydrogen bond and (E / Z) isomerisation about an exocyclic double bond. • The isomerism was investigated by 1H-, 13C-, 15N- and 19F-NMR spectroscopy in different solvents. • Gibbs free energies (ΔG) and Free activation energies (ΔG≠) were calculated based on DFT computations. [ABSTRACT FROM AUTHOR]

Herein we present a new strategy for the oxidative synthesis of formamides from various types of amines and bioderived formyl sources (DHA, GLA and GLCA) and molecular oxygen (O2) as oxidant on g‐C3N4 supported Cu catalysts. Combined characterization data from EPR, XAFS, XRD and XPS revealed the formation of single CuN4 sites on supported Cuphen/C3N4 catalysts. EPR spin trapping experiments disclosed ⋅OOH radicals as reactive oxygen species and ⋅NR1R2 radicals being responsible for the initial C−C bond cleavage. Control experiments and DFT calculations showed that the successive C−C bond cleavage in DHA proceeds via a reaction mechanism co‐mediated by ⋅NR1R2 and ⋅OOH radicals based on the well‐equilibrated CuII and CuI cycle. Our catalyst has much higher activity (TOF) than those based on noble metals. [ABSTRACT FROM AUTHOR]

Herein we present a new strategy for the oxidative synthesis of formamides from various types of amines and bioderived formyl sources (DHA, GLA and GLCA) and molecular oxygen (O2) as oxidant on g‐C3N4 supported Cu catalysts. Combined characterization data from EPR, XAFS, XRD and XPS revealed the formation of single CuN4 sites on supported Cuphen/C3N4 catalysts. EPR spin trapping experiments disclosed ⋅OOH radicals as reactive oxygen species and ⋅NR1R2 radicals being responsible for the initial C−C bond cleavage. Control experiments and DFT calculations showed that the successive C−C bond cleavage in DHA proceeds via a reaction mechanism co‐mediated by ⋅NR1R2 and ⋅OOH radicals based on the well‐equilibrated CuII and CuI cycle. Our catalyst has much higher activity (TOF) than those based on noble metals. [ABSTRACT FROM AUTHOR]

The racemization tendency of acyclic P‐chirogenic phosphanes is investigated experimentally and theoretically. Results of these investigations are important for the construction and use of P‐chirogenic ligands and organocatalysts frequently used in asymmetric syntheses. Proof is given that triaryl phosphanes undergo easier racemization than compounds in which the phosphorus atom is linked to alkyl substituents. Interestingly, bulky ortho aryl substituents have only a marginal effect, whereas P‐naphthyl rings destabilize the compound. [ABSTRACT FROM AUTHOR]

The mechanism of acetonitrile and methyl benzoate catalytic hydrogenation using pincer catalysts M(H)2(CO)[NH(C2H4P iPr2)2] ( 1M) and M(H)(CO)[N(C2H4P iPr2)2] ( 2M) (M = Fe, Ru, Os) has been computed at various levels of density functional theory. The computed equilibrium between 1Fe and 2Fe agrees perfectly with the experimental observations. On the basis of the activation barriers and reaction energies, the best catalysts for acetonitrile hydrogenation are 1Fe/2Fe and 1Ru/2Ru, and the best catalysts for methyl benzoate hydrogenation are 1Ru/2Ru. The best catalysts for the dehydrogenation of benzyl alcohol are 1Ru/2Ru. It is to note that the current polarizable continuum model is not sufficient in modeling the solvation effect in the energetic properties of these catalysts as well as their catalytic properties in hydrogenation reaction, as no equilibrium could be established between 1Fe and 2Fe. Comparison with other methods and procedures has been made. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)‐BEt3 adducts. By applying complexes 3 with KHBEt3 as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N‐heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt3 as cocatalyst. [ABSTRACT FROM AUTHOR]

The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)‐BEt3 adducts. By applying complexes 3 with KHBEt3 as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N‐heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt3 as cocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: We herein report on the different coordination behavior of phosphite–olefin ligands containing either a terminal olefin moiety or a related compound containing an internal olefin moiety to a CpCo(I)-center. While the former coordinates to the metal center via P atom and olefin moiety upon irradiation, photolysis of the latter led to the subsequent formation of the phosphorus-free [CpCo(η4-1,3-butadiene)] complex (6). A mechanistic rational of the decomposition reaction based on an Arbuzov-like rearrangement is suggested. [Copyright &y& Elsevier]

Abstract: The behaviour on keto–enol tautomeric equilibration of ethyl 2-benzoyl-5-(2-furyl)-3-hydroxy-penta-2,4-dienoate (1) and ethyl 2-acetyl-3-hydroxy-5-phenyl-penta-2,4-dienoate (2) was investigated by 1H and 13C NMR spectroscopy in different solvents and BP86/TZVP density functional theory computations. The spectral assignment to enol and keto tautomers was performed with one- and two-dimensional techniques. The percentage of the keto form in the tautomeric equilibrium depends on solvents and rises by increasing solvent polarity. The enol–enol tautomerism is also discussed on the basis of the coupling constants 2 J C,OH, 3 J C,OH and 4 J H,OH, respectively. [Copyright &y& Elsevier]

Iridium catalysis, vinyl ethers, transfer vinylation, bio-based alcohols, 2-MeTHF Front Cover Picture: Use of Iridium-Catalyzed Transfer Vinylation for the Synthesis of Bio-Based (bis)-Vinyl Ethers (Adv. Keywords: Iridium catalysis; vinyl ethers; transfer vinylation; bio-based alcohols; 2-MeTHF EN Iridium catalysis vinyl ethers transfer vinylation bio-based alcohols 2-MeTHF 1211 1211 1 04/01/22 20220330 NES 220330 The B front cover picture b depicts bio-based bis-vinyl ether structures which were synthesized through a catalytic transfer vinylation reaction, where a cationic iridium complex was used as the catalyst, sodium acetate as the base, vinyl acetate as the vinylating agent, and 2-MeTHF as a green solvent. [Extracted from the article]

• Investigation of degradation products of clopidogrel hydrogen sulfate under ICH prescribed peroxide-mediated oxidative stress testing conditions. • First report regarding the characterization and NMR spectral assignment of the diastereomeric degradation product N -oxide. • The signals of the CH 2 groups in the diastereomeric degradation appear influenced by the polarization of the N O bond. • DFT calculations were used to understand the intramolecular magnetic effects. In this work, we enriched the major oxidative degradation product of clopidogrel hydrogen sulfate with the addition of 2.0 equiv. of peroxymonosulfate and analyzed the diastereomers in situ with 1D NMR (1H and 13C) and 2D NMR (1H−1H COSY, 1H−13C HSQC and 1H−13C HMBC). We observed that the signal from the CH 2 groups at the positions 4, 6 and 7 in the degradation products (S)-5-((S)-1-(2-chlorophenyl)-2‑methoxy-2-oxoethyl)-5‑hydroxy-4,5,6,7-tetrahydrothieno[3,2-c]pyridin-5-ium and their analog diastereomer (5 R ,10 S) are associated with the polarization of the N O bond in the piperidine ring. Depending on the conformation of this cyclic moiety, an intramolecular anisotropic effect between the phenyl ring and the methylene groups H-4 and H-6 affected the multiplicities and the chemical shifts of these oxidative degradation products in the 1H and 13C NMR spectra. We used DFT calculations to understand the pattern of the 1H NMR chemical shifts, the energies of diastereomers conformations and their intramolecular magnetic effects. [ABSTRACT FROM AUTHOR]

CpCoI-olefin-phosphite and CpCoI-bisphosphite complexes were systematically prepared and their reactivity in [2+2+2] cycloaddition reactions compared with highly active [CpCo(H2CCHSiMe3)2] ( 1). Whereas 1 is an excellent precursor for the synthesis of [CpCo(olefin)(phosphite)] complexes ( 2 a- f), [CpCo(phosphite)2] complexes ( 3 a- e) were prepared photochemically from [CpCo(cod)]. The complexes were evaluated in the cyclotrimerization reaction of diynes with nitriles yielding pyridines. For [CpCo(olefin)(phosphite)], as well as some of the [CpCo(phosphite)2] complexes, reaction temperatures as low as 50 °C were sufficient to perform the cycloaddition reaction. A direct comparison showed that the order of reactivity for the complex ligands was olefin2>olefin/phosphite>phosphites2. The complexes with mixed ligands favorably combine reactivity and stability. Calculations on the ligand dissociation from [CpCo(olefin)(phosphite)] proved that the phosphite is dissociating before the olefin. [CpCo(H2CCHSiMe3){P(OPh)3}] ( 2 a) was investigated for the co-cyclization of diynes and nitriles and found to be an efficient catalyst at rather mild temperatures. [ABSTRACT FROM AUTHOR]

A general and efficient method for the palladium-catalyzed carbonylative coupling of aryl iodides to benzyl acetylenes has been developed. Various furanones have been prepared in excellent yields from their corresponding benzyl acetylenes at room temperature under a CO atmosphere. For aliphatic alkynes, their corresponding alkynones were obtained in good yields. Detailed DFT calculations have also been carried out to understand the reaction pathway and the most probable reaction mechanism has been proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first example of allylic silylation of allyl acetate via silyl radical enabled by a dual photoredox/nickel catalysis. • The challenge of the compatibility between the photo-induced formation of silyl radicals and nickel catalysis was overcome. • Various critical substance class of allysilanes with broad substrate scope were obtained in moderate to excellent yields. • Mechanistic studies and DFT computation explained the plausible pathway and the control of regioselectivity and the stereoselectivity. The compatibility between photogenerated silyl radicals and transition metal catalysis remains one of the foremost challenges in modern synthetic organic chemistry. Herein, we present the cooperation of photoredox/nickel catalyzed allylic silylation of diverse allyl acetates (even with multiple alkenyl groups) via a silyl radical intermediate. This protocol successfully surmounts the long-standing challenge and provides straightforward, modular synthetic access to substituted allylsilanes from silanecarboxylic acids. Moreover, this strategy has advantages of green and mild conditions over established nucleophilic substitution methods via a silanion pathway. Mechanistic study shows that the formation of silyl radical initiated by photo-induced decarboxylation of silanecarboxylic acids, and the nickel-catalyzed oxidative addition of allyl acetate, followed by silyl radical addition are critical processes. DFT computation reveals that the regioselectivity is controlled by the silyl radical attack of the sterically less hindered or less substituted terminal allylic carbon atom. [ABSTRACT FROM AUTHOR]

Abstract: The epimerization of chiral lactides was studied in the presence of various homogeneous and heterogeneous bases. Some solvent/base systems were found to promote epimerization at room temperature efficiently. Side reactions such as polymerization were not observed or occurred only slowly. This new protocol offers the opportunity of the transformation of meso-lactide into rac-lactide. Therefore it can reduce the overall manufacturing costs of polylactides, a problem which currently hampers the broad application of those environmentally friendly polymers in a large scale. [Copyright &y& Elsevier]

Abstract: Adsorption of reaction intermediates appearing during CO hydrogenation at the sulfur covered MoS2(10−10) surfaces, Mo-termination with 42% S coverage and S-termination with 50% S coverage, are investigated systematically using periodic density functional theory methods. Computed vibrational frequencies of all intermediates are compared with observed data from infrared (IR) spectroscopy allowing a detailed interpretation and assignment of the different features in the experimental spectra. The pathway for CO hydrogenation on both terminations has been studied in detail where the most likely reaction path involves C1 type surface species in the sequence CO→CHO→CH2O→CH2OH→CH2 →CH3 →CH4 in agreement with the experiment. [Copyright &y& Elsevier]

Abstract: Various Ru(L1)(L2) (1) complexes (L1 =2,2′-bipyridines, 2,2′:6′,2″-terpyridines, 6-(4S)-4-phenyl-4,5-dihydro-oxazol-2-yl-2,2′-bipyridinyl or 2,2′-bipyridinyl-6-carboxylate; L2 =pyridine-2,6-dicarboxylate, pyridine-2-carboxylate or 2,2′-bipyridinyl-6-carboxylate) have been synthesized (or in situ generated) and tested on epoxidation of olefins utilizing 30% aqueous H2O2. The complexes containing pyridine-2,6-dicarboxylate show extraordinarily high catalytic activity. Based on the stereoselective performance of chiral ruthenium complexes containing non-racemic 2,2′-bipyridines including 6-[(4S)-4-phenyl-4,5-dihydro-oxazol-2-yl]-[2,2′]bipyridinyl new insights on the reaction intermediates and reaction pathway of the ruthenium-catalyzed enantioselective epoxidation are proposed. In addition, a simplified protocol for epoxidation of olefins using urea hydrogen peroxide complex as oxidizing agent has been developed. [Copyright &y& Elsevier]

The reaction of (Cp*ReH2)2B4H4 with monoborane leads to the sequential formation of (Cp*Re)2BnHn (n = 7-10, 1-4). These species adopt closed deltahedra with the same total connectivities as the closo-borane anions [BnHn]2-, n = 9-12, but with flattened geometries rather than spherical shapes. These rhenaborane clusters are characterized by high metal coordination numbers, Re-Re cross-cluster distances within the Re-Re single bond range, and formal cluster electron counts three skeletal electron pairs short of that required for a canonical closo-structure of the same nuclearity. An open cluster, (Cp*ReH)2B2H9 (5), is isolated that bears the same structural relationship to arachno-B2H15 as 1-4 bear to the closo-borane anions. Chloroborane permits the isolation of (Cp*ReH)2B5Cl5 (6), an isoelectronic chloroanalogue of known open (Cp*WH2)2B5Cl5 and (Cp*Re)2B6H4Cl2 (7), a triple-decker complex containing a planar, six-membered 1 ,2-B6H6C12 ring. Both are putative five- and six-boron intermediates in the formation of 1. Electronic structure calculations (extended Hückel and density functional theory) yield geometries in agreement with the structure determinations, large HOMO-LUMO gaps in accord with the high stabilities, and 11B chemical shifts accurately reflecting the observed shifts. Analyses of the bonding in 1-4 reveal that the Cp*Re...Cp*Re interaction generates fragment orbitals that are able to contribute the "missing" three skeletal electron pairs required for skeletal bonding. The necessity of a Re...Re interaction for strong cluster bonding requires a borane fragment shape change to accommodate it, thereby explaining the noncanonical geometries. Application of the debor principle of borane chemistry to the shapes of 1-4 readily rationalizes the observed geometries of 5 and 6. This evidence of the scope of transition metal fragment control of borane geometry suggests the existence of a large class of metallaboranes with structures not found in known borane or metal clusters. [ABSTRACT FROM AUTHOR]

B3LYP/6-31G* density functional theory calculations have been carried out on the structure and stability of seven B24N24 clusters. It is found that the new proposed isomer with two octagons, sixteen hexagons and eight squares in S8 symmetry is more stable than the isomer with six octagons, eight hexagons and twelve squares in O symmetry by 60.4 kcal/mol, and the isomer with twenty hexagons and six squares in S4 symmetry by 2.8 kcal/mol. The fullerene-like isomer is much higher in energy (148.6 kcal/mol). [Copyright &y& Elsevier]

Evaluates the aromaticity and antiaromaticity of oligocyclic annelated five-membered ring systems, and related compounds. Identification of the five-membered ring systems; Observation of pentalene upon matrix isolation at -196 degrees Celsius; Demonstration of the existence of the highly strained acepentalene with 10pi electrons.

Compares many nitrogen species and identifies pentazole derivatives as being the thermodynamically most stable polynitrogen compounds. Result of experiments on polynitrogen molecules at high levels of ab initio and density functional theory (DFT); Ab initio and DFT computations; Relative stability and geometry; Computed energetic increments for polynitrogen compounds.

Assesses the aromaticity and antiaromaticity of the cations and anions derived from cyclopentadiene, indene and fluorene. Utilization of high level ab initio and density functional theory computations; Aromaticity of the anions with benzene, naphthalene and anthracene; Magnitude of the delocalization energies of aromatic cations.

Predicts the appreciable electrostatic acceleration of the cyclization of 1,3-cis-5-hexatriene to 1,3-cyclohexadiene by Li+ complexation. Magnetic criterion of aromaticity of the cyclization transition state; Influence of solvent complexation; Acceleration of 1,5-H shift in cyclopentadiene (CPD).

Reports that the presence of two (4n+2)-electron conjugated systems in perpendicular planes results in considerable aromatic stabilization. How the 3,5-dehydrophenyl cation is stabilized; Possibility of analogous refoil 3c-2e bonding in other systems with pi perimeters.

Valuable formamides were "pulled out of the hat" upon reaction of amines with biomass‐based starting materials such as 1,3‐dihydroxyacetone, glycolaldehyde and glycerolaldehyde by avoiding any waste products using environmentally benign oxygen as oxidant, as reported by Haijun Jiao, Feng Shi, Jabor Rabeah, Angelika Brückner et al. in their Research Article (e202402241). This reaction may be regarded as "green" and somehow "magic"...By Xingchao Dai; Yunyan Han; Haijun Jiao; Feng Shi; Jabor Rabeah and Angelika BrücknerReported by Author; Author; Author; Author; Author; Author [Extracted from the article]

Valuable formamides were "pulled out of the hat" upon reaction of amines with biomass‐based starting materials such as 1,3‐dihydroxyacetone, glycolaldehyde and glycerolaldehyde by avoiding any waste products using environmentally benign oxygen as oxidant, as reported by Haijun Jiao, Feng Shi, Jabor Rabeah, Angelika Brückner et al. in their Research Article (e202402241). This reaction may be regarded as "green" and somehow "magic"...By Xingchao Dai; Yunyan Han; Haijun Jiao; Feng Shi; Jabor Rabeah and Angelika BrücknerReported by Author; Author; Author; Author; Author; Author [Extracted from the article]

A novel one‐pot iridium‐catalyzed domino hydroxymethylation of olefins, which relies on using two different ligands at the same time, is reported. DFT computation reveals different activities for the individual hydroformylation and hydrogenation steps in the presence of mono‐ and bidentate ligands. Whereas bidentate ligands have higher hydrogenation activity, monodentate ligands show higher hydroformylation activity. Accordingly, a catalyst system is introduced that uses dual ligands in the whole domino process. Control experiments show that the overall selectivity is kinetically controlled. Both computation and experiment explain the function of the two optimized ligands during the domino process. [ABSTRACT FROM AUTHOR]

The nature of the support can fundamentally affect the function of a heterogeneous catalyst. For the novel type of isolated metal atom catalysts, sometimes referred to as single‐atom catalysts, systematic correlations are still rare. Here, we report a general finding that Pd on nitride supports (non‐metal and metal nitride) features a higher oxidation state compared to that on oxide supports (non‐metal and metal oxide). Through thorough oxidation state investigations by X‐ray absorption spectroscopy (XAS), X‐ray photoelectron spectroscopy (XPS), CO‐DRIFTS, and density functional theory (DFT) coupled with Bader charge analysis, it is found that Pd atoms prefer to interact with surface hydroxyl group to form a Pd(OH)x species on oxide supports, while on nitride supports, Pd atoms incorporate into the surface structure in the form of Pd−N bonds. Moreover, a correlation was built between the formal oxidation state and computational Bader charge, based on the periodic trend in electronegativity. [ABSTRACT FROM AUTHOR]

The nature of the support can fundamentally affect the function of a heterogeneous catalyst. For the novel type of isolated metal atom catalysts, sometimes referred to as single‐atom catalysts, systematic correlations are still rare. Here, we report a general finding that Pd on nitride supports (non‐metal and metal nitride) features a higher oxidation state compared to that on oxide supports (non‐metal and metal oxide). Through thorough oxidation state investigations by X‐ray absorption spectroscopy (XAS), X‐ray photoelectron spectroscopy (XPS), CO‐DRIFTS, and density functional theory (DFT) coupled with Bader charge analysis, it is found that Pd atoms prefer to interact with surface hydroxyl group to form a Pd(OH)x species on oxide supports, while on nitride supports, Pd atoms incorporate into the surface structure in the form of Pd−N bonds. Moreover, a correlation was built between the formal oxidation state and computational Bader charge, based on the periodic trend in electronegativity. [ABSTRACT FROM AUTHOR]

Investigates [5]pericyclynes at high ab initio and density functional levels. Geometric, energetic and magnetic criteria of aromaticity; Negligibility in strain energy of [5]pericyclynes; Destablization in an ab initio study on the parent system; Comprehensive theoretical investigation of the possible homoaromatic character.

Studies the structures of the 12-vertex oxa-an thia-nido-dodecaborates and B13 H13 2. Experimental procedure used; Results of the study.

Lithiumcyclopentadienide, previously identified to be an endless polymer in the ligand-free solid state, was investigated by 13C- and 6Li-CP/MAS NMR spectra, and by B3LYP-GIAO theoretical calculations. By spectra simulation, the axially symmetric 13C-shift tensor components were identified to be δ11 = δ22 = 151.5 ppm, δ33 = 15.5 ppm. The 6Li-tensor components are δ11 = δ22 = +1.0 ppm, δ33 = −43.0 ppm. This extremely high field component is due to cumulative ring current effects. B3LYP-GIAO/TZVP calculations on the tensor principal components agree remarkably well with the measurements. A new and very simple method of preparing air-sensitive compounds for solid-state NMR analyses is described. [ABSTRACT FROM AUTHOR]

Abstract: Commercially available Ru‐MACHOTM‐BH is an active catalyst for the hydrogenation of several functional groups and for the dehydrogenation of alcohols. Herein, we report on the new application of this catalyst to the base‐free transfer hydrogenation of carbonyl compounds. Ru‐MACHOTM‐BH proved to be highly active and selective in this transformation, even with α,β‐unsaturated carbonyl compounds as substrates. The corresponding aliphatic, aromatic and allylic alcohols were obtained in excellent yields with catalyst loadings as low as 0.1–0.5 mol % at mild temperatures after very short reaction times. This protocol tolerates iPrOH and EtOH as hydrogen sources. Additionally, scale up to multi‐gram amounts was performed without any loss of activity or selectivity. An outer‐sphere mechanism has been proposed and the computed kinetics and thermodynamics of crotonaldehyde and 1‐phenyl‐but‐2‐en‐one are in perfect agreement with the experiment. [ABSTRACT FROM AUTHOR]

Describes an ab initio self-consistent reaction field study of medium effects on the geometries of donor-acceptor complexes. N-B separation; Dipole moment measurements; Bond lengths; Bond angles; Crystal dipolar field interaction.

The article presents the molecular structure of the reactivity and stability of CpCoI complexes as catalysts for cycloaddition reactions using systematic ligand variations.

This is a general and efficient method for the preparation of furan-2-ones and alkynones under mild conditions in good to excellent yields. [ABSTRACT FROM AUTHOR]

The palladium-catalyzed chemoselective carbonylation of bromoaryl triflates is reported. The selective C−Br bond versus C−OTf (OTf=triflate) bond functionalization can be remarkably tuned by the combination of the ligand [4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) vs. 1,1′-bis(diphenylphosphino)ferrocene (DPPF)] and the solvent (toluene vs. DMSO). The respective ligand and solvent effects are rationalized by DFT calculations. In contrast, the monodentate ligands BuPAd2 and tBu3P prefer the selective C−Br bond activation and are solvent insensitive. [ABSTRACT FROM AUTHOR]

The first manganese-catalyzed hydrogenation of esters to alcohols has been developed. The combination of Mn(CO)5Br with [HN(CH2CH2P(Et)2)2] leads to a mixture of cationic and neutral Mn PNP pincer complexes, which enable the reduction of various ester substrates, including aromatic and aliphatic esters as well as diesters and lactones. Notably, related pincer complexes with isopropyl or cyclohexyl substituents showed very low activity. [ABSTRACT FROM AUTHOR]

The first manganese-catalyzed hydrogenation of esters to alcohols has been developed. The combination of Mn(CO)5Br with [HN(CH2CH2P(Et)2)2] leads to a mixture of cationic and neutral Mn PNP pincer complexes, which enable the reduction of various ester substrates, including aromatic and aliphatic esters as well as diesters and lactones. Notably, related pincer complexes with isopropyl or cyclohexyl substituents showed very low activity. [ABSTRACT FROM AUTHOR]

Manganese‐catalyzed hydrogenation reactions have aroused widespread interest in recent years. Among the catalytic systems described, especially PNP‐ and NNP–Mn pincer catalysts have been reported for the hydrogenation of aldehydes, ketones, nitriles, aldimines and esters. Furthermore, NNP−Mn pincer compounds are efficient catalysts for the hydrogenolysis of less reactive amides, ureas, carbonates, and carbamates. Herein, the synthesis and application of specific imidazolylaminophosphine ligands and the corresponding Mn pincer complexes are described. These new catalysts have been characterized and studied by a combination of experimental and theoretical investigations, and their catalytic activities have been tested in several hydrogenation reactions with good to excellent performance. Especially, the reduction of N‐heterocycles can be performed under very mild conditions. [ABSTRACT FROM AUTHOR]

The famous aromaticity index NICS (nucleus independent chemical shift) was introduced 25 years ago. The authors use this anniversary for a short and to some degree personal retrospective. [ABSTRACT FROM AUTHOR]

Selective catalytic reductions of nitriles are presented using the commercially available Ru-Macho-BH complex. A variety of aliphatic, aromatic and (hetero)cyclic nitriles including industrially important adipodinitrile are hydrogenated to the corresponding primary amines. Modelling suggests the reaction follows an outer sphere hydrogenation mechanism. [ABSTRACT FROM AUTHOR]

The direct asymmetric reductive amination (DARA) of ketones with anilines is described by combining a chiral Brønsted acid (TRIP) and the non-chiral Knölker iron complex as the catalyst system. In situ-formed imines are reduced with molecular hydrogen to give chiral amines in high yields (90%) and enantioselectivities of up to 99% ee. [ABSTRACT FROM AUTHOR]

The first selective iridium-catalyzed hydrogenations of esters are presented. By using a commercially available iridium pincer complex more than 20 different aromatic, aliphatic, and (hetero)cyclic esters are reduced to the corresponding alcohols in moderate to very good yields. An outer-sphere mechanism is proposed on the basis of our computational analysis. [ABSTRACT FROM AUTHOR]

Deuterated organic molecules provide the basis for many applications in life sciences and material research. Thus, methodologies to access labeled compounds with defined selectivity continue to be important. Using KOtBu as base and DMSO‐d6 as deuterium source, we present a general and applicable method for the selective deuteration of a set of nitrogen‐containing heterocycles (pyridines, azines and bioactive molecules). Experimental and DFT mechanistic studies indicate that this reaction proceeds via deprotonation of the substrates by the dimsyl anion. The relative thermodynamic stability of the heterocycle anions determines the distribution and degree of deuteration. [ABSTRACT FROM AUTHOR]

In this review, we have mainly shown the recent computational studies on formic acid adsorption and selective dissociation to produce hydrogen (NCOOH → CO2 + H2) on several metal (Pt, Pd, Ni, Cu, Rh and Au) and metal oxide (TiO2, MgO, ZnO and NiO) surfaces, and both thermal decomposition and electro-catalytic oxidation have been discussed. The decomposition mechanisms of formic acid have been studied by using different computational models and methods, not only interesting and exciting but also different and controversial results have been reported. It is noted that the model systems used in these studies are too simple and idealized, and they cannot represent the real catalysts or the catalytic systems, and more sophisticated computational methodologies and real model systems under the consideration of the working conditions are therefore needed. [ABSTRACT FROM AUTHOR]

The CC coupling of aryl nitriles at Group 4 metallocenes leads to unusual ring‐strained 1‐metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes. The structural, energetic, and chemical properties of these complexes are described. The reactions of these compounds towards CH3CN, H2, CO2, and HCl usually lead to the release of one nitrile and its replacement by different co‐substrates. [ABSTRACT FROM AUTHOR]