Search

Deuterated organic molecules are of interest for many applications ranging from mechanistic investigations in basic organic and physical chemistry to the development of new pharmaceuticals. Thus, methodologies for isotope-labelling reactions continue to be important. Here, a convenient methodology for hydrogen/deuterium exchange reactions in electron-rich arenes is reported using simple iron salts and deuterium oxide as isotope source. [ABSTRACT FROM AUTHOR]

The catalytic hydrogenation of esters and carboxylic acids represents a fundamental and important class of organic transformations, which is widely applied in energy, environmental, agricultural, and pharmaceutical industries. Due to the low reactivity of the carbonyl group in carboxylic acids and esters, this type of reaction is, however, rather challenging. Hence, specifically active catalysts are required to achieve a satisfactory yield. Nevertheless, in recent years, remarkable progress has been made on the development of catalysts for this type of reaction, especially heterogeneous catalysts, which are generally dominating in industry. Here in this review, we discuss the recent breakthroughs as well as milestone achievements for the hydrogenation of industrially important carboxylic acids and esters utilizing heterogeneous catalysts. In addition, related catalytic hydrogenations that are considered of importance for the development of cleaner energy technologies and a circular chemical industry will be discussed in detail. Special attention is paid to the insights into the structure–activity relationship, which will help the readers to develop rational design strategies for the synthesis of more efficient heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Novel catalytic systems based on pentacarbonylmanganese bromide and stable NNN-pincer ligands are presented for the transfer-dehydrogenation of secondary alcohols to give the corresponding ketones in good to excellent isolated yields. Best results are obtained using di-picolylamine derivatives as ligands and acetone as an inexpensive hydrogen acceptor. Besides high activity for benzylic substrates, aliphatic alcohols, as well as steroid derivatives, are readily oxidized in the presence of the optimal phosphorus-free catalyst. [ABSTRACT FROM AUTHOR]

The asymmetric transfer hydrogenation of ketones using isopropyl alcohol (IPA) as hydrogen donor in the presence of novel manganese catalysts is explored. The selective and active systems are easily generated in situ from [MnBr(CO)5 ] and inexpensive C 2-symmeric bisoxalamide ligands. Under the optimized reaction conditions, the Mn-derived catalyst gave higher enantioselectivity compared with the related ruthenium catalyst. [ABSTRACT FROM AUTHOR]

Non‐noble metal catalysts based on pincer type compounds are of special interest for organometallic chemistry and organic synthesis. Next to iron and manganese, currently cobalt–pincer type complexes are successfully applied in various catalytic reactions. In this review the recent progress in (de)hydrogenation, transfer hydrogenation, hydroboration and hydrosilylation as well as dehydrogenative coupling reactions using cobalt–pincer complexes is summarised. Feeling the pinch! In this review, we describe the recent progress of cobalt–pincer‐type catalysts. Besides their synthesis and general reactivity, specific catalytic applications are summarised including (de)hydrogenations, transfer (de)hydrogenations, hydroborations and hydrosilylation reactions. [ABSTRACT FROM AUTHOR]

Reduction of various nitroarenes in the presence of heterogeneous iron oxide-based catalyst Fe2O3/NGr@C under water-gas shift reaction (WGSR) conditions has been demonstrated. The catalytic material is prepared in a straightforward manner via deposition/pyrolysis of iron-phenanthroline complex on carbon support. It shows high chemoselectivity towards the reduction of nitroarenes in the presence of other reducible and/or poisoning-capable functional groups. Hydrogenation is achieved using CO/H2O as a hydrogen source. Furthermore, it is demonstrated that the presence of triethylamine additive has a significant positive effect on the rate of reduction. [ABSTRACT FROM AUTHOR]

The structures and stability of the designed PNP pincer amido M(NO) 2 (PNP) and amino H M(NO) 2 (PN H P) complexes [M = V, Nb, and Ta, PNP = N(CH 2 CH 2 P(isopropyl) 2 ) 2 , PN H P = HN(CH 2 CH 2 P(isopropyl) 2 ) 2 ] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H 2 environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-C N, Ph-CH NH, Ph-CH NH-Ph, Ph-CH N CH 2 Ph, Ph-C CH, Ph-CH CH 2 , Ph-CHO, and Ph-CO CH 3 , the reaction prefers either a two-step or one-step mechanism for the hydridic M H and protonic N H transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges. [ABSTRACT FROM AUTHOR]

Abstract: A selection of cobalt(I) and cobalt(II) pincer type complexes with different substitution patterns was tested in the catalytic reduction of carboxylic acid esters to alcohols. The cobalt pincer type complex 4 is suitable for the hydrogenation of aromatic as well as aliphatic and cyclic esters. Mechanistic investigation indicated a metal ligand cooperated reaction pathway. [ABSTRACT FROM AUTHOR]

A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30-40 °C, 4 h, 30 bar H2). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry. [ABSTRACT FROM AUTHOR]

A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30-40 °C, 4 h, 30 bar H2). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry. [ABSTRACT FROM AUTHOR]

Base-metal catalysis, especially with non-noblemetal pincer-type catalysts, is increasingly used in organic synthesis and thus becoming more and more important for organometallic chemistry. After ruthenium-, iridium- and ironbased pincer-type complexes became established as state-of-the-art catalysts for (de)hydrogenation reactions in the past decade, manganese complexes have most recently been successfully applied in related transformations. Specifically, this microreview covers their recent progress in (de)hydrogenation and transfer (de)hydrogenation as well as in C-C and C-X bondforming reactions. [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]

Cooperative catalysis by [Pd(dba)2] and the chiral phosphoric acid BA1 in combination with the phosphoramidite ligand L8 enabled the efficient enantioselective amination of racemic allylic alcohols with a variety of functionalized amines. This catalytic protocol is highly regio- and stereoselective (up to e.r. 96:4) and furnishes valuable chiral amines in almost quantitative yield. [ABSTRACT FROM AUTHOR]

Cooperative catalysis by [Pd(dba)2] and the chiral phosphoric acid BA1 in combination with the phosphoramidite ligand L8 enabled the efficient enantioselective amination of racemic allylic alcohols with a variety of functionalized amines. This catalytic protocol is highly regio- and stereoselective (up to e.r. 96:4) and furnishes valuable chiral amines in almost quantitative yield. [ABSTRACT FROM AUTHOR]

A straightforward process for the N-alkylation of amines has been developed applying readily available carboxylic acids and silanes as the hydride source. Complementary to known reductive aminations, effective C–N bond construction proceeds under mild conditions and allows obtaining a broad range of alkylated secondary and tertiary amines, including fluoroalkyl-substituted anilines as well as the bioactive compound Cinacalcet HCl. [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]

We present the first base-free Fe-catalyzed ester reduction applying molecular hydrogen. Without any additives, a variety of carboxylic acid esters and lactones were hydrogenated with high efficiency. Computations reveal an outer-sphere mechanism involving simultaneous hydrogen transfer from the iron center and the ligand. This assumption is supported by NMR experiments. [ABSTRACT FROM AUTHOR]

Wir präsentieren die erste basenfreie Fe ‐ katalysierte Esterreduktion unter Verwendung von molekularem Wasserstoff. Eine Vielzahl von Carbonsäureestern und Lactonen konnte ohne den Einsatz von Additiven sehr effizient hydriert werden. Auf Grundlage von DFT ‐ Rechnungen und unterstützenden NMR ‐ spektroskopischen Experimenten wird ein Außensphärenmechanismus diskutiert. Bei diesem erfolgt ein simultaner Übergang des Wasserstoffs vom Eisenzentrum und dem Liganden. Fe ‐ nomenal: Ein neues und effizientes Katalysatorsystem für die Hydrierung von verschiedenen aromatischen und aliphatischen Carbonsäureestern sowie Lactonen zu den jeweiligen Alkoholen unter Verwendung des Eisenkomplexes 1 wurde entwickelt. Es wird postuliert, dass die Reaktion über einen Außensphärenmechanismus verläuft. [ABSTRACT FROM AUTHOR]

A general catalytic protocol for the methylation of amines has been developed applying, for the first time, formic acid as the C1 building block and silanes as reducing agents. A broad range of aromatic and aliphatic, both primary and secondary, amines has been converted to the corresponding tertiary amines including [ N-13C]-labelled drugs in good to excellent yields under mild conditions. [ABSTRACT FROM AUTHOR]

The platinum-catalyzed hydrosilylation of amides to afford amines selectively is reported. By using defined platinum/N-heterocyclic carbene complexes, the reduction of secondary and tertiary amines takes place under mild conditions. [ABSTRACT FROM AUTHOR]

A convenient and efficient catalyst system for the hydrogenation of aliphatic nitriles towards the corresponding primary amines in high to excellent yields is presented. In addition, aromatic nitriles are reduced smoothly, too. The use of low catalyst loadings and molecular hydrogen make this protocol an attractive methodology. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed hydroamination reactions are sustainable and atom-economical CN bond-forming processes. Although remarkable progress has been made in the inter- and intramolecular amination of olefins and 1,3-dienes, related intermolecular reactions of amides are still much less known. Control of the regioselectivity without analogous telomerization is the particular challenge in the catalytic hydroamidation of alkenes and 1,3-dienes. Herein, we report a general protocol for the hydroamidation of electron-deficient N-heterocyclic amides and sulfonamides with 1,3-dienes and vinyl pyridines in the presence of a catalyst derived from [{Pd(π-cinnamyl)Cl}2] and ligand L7 or L10. The reactions proceeded in good to excellent yield with high regioselectivity. The practical utility of our method is demonstrated by the hydroamidation of functionalized biologically active substrates. The high regioselectivity for linear amide products makes the procedure useful for the synthesis of a variety of allylic amides. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed hydroamination reactions are sustainable and atom-economical CN bond-forming processes. Although remarkable progress has been made in the inter- and intramolecular amination of olefins and 1,3-dienes, related intermolecular reactions of amides are still much less known. Control of the regioselectivity without analogous telomerization is the particular challenge in the catalytic hydroamidation of alkenes and 1,3-dienes. Herein, we report a general protocol for the hydroamidation of electron-deficient N-heterocyclic amides and sulfonamides with 1,3-dienes and vinyl pyridines in the presence of a catalyst derived from [{Pd(π-cinnamyl)Cl}2] and ligand L7 or L10. The reactions proceeded in good to excellent yield with high regioselectivity. The practical utility of our method is demonstrated by the hydroamidation of functionalized biologically active substrates. The high regioselectivity for linear amide products makes the procedure useful for the synthesis of a variety of allylic amides. [ABSTRACT FROM AUTHOR]

A novel catalytic system formed from Fe(stearate)2/NH2CH2CH2NH2 and polymethylhydrosiloxane was directly developed for the hydrosilylation of carboxylic acid esters to alcohols. The catalytic method exhibits broad substrate scope, including 20 aliphatic, aromatic, and heterocyclic esters. The corresponding alcohols are obtained in moderate to very good yields. [ABSTRACT FROM AUTHOR]

A convenient and practical copper-catalyzed reductive amination was discovered. In the presence of easily available and inexpensive Cu(OAc)2 various ketones react with anilines and molecular hydrogen to give the desired amines in high yields. [ABSTRACT FROM AUTHOR]

The synthesis of phosphine-imidazolyl ligands 1 and 2 in good yields is presented. In combination with [{Ru(benzene)Cl2}2], ligands 1 c and 1 e formed efficient catalyst systems for the selective hydrogenation of various carboxylic esters into their corresponding primary alcohols. Furthermore, the structures of four ruthenium complexes with ligands 1 b, 1 c, 1 d, and 1 e were determined by X-ray crystallography, which showed the formation of different coordination modes depending on the ligand structure. [ABSTRACT FROM AUTHOR]

With respect to its availability, low toxicity, and price iron should be one of the most used metals in homogeneous catalysis. Surprisingly, so far the application of iron is underdeveloped in comparison to other transition metals. Herein, we highlight promising attempts obtained in hydrogenation, transfer hydrogenation and hydrosilylation, which nicely illustrate the potential of iron and hopefully initialize a ferric future for catalysis. [ABSTRACT FROM AUTHOR]

Abstract: A novel defined iron catalyst for the epoxidation of aromatic and aliphatic olefins with hydrogen peroxide as the terminal oxidant is described. Our catalyst approach is based on bio-inspired both alkyl- and aryl-substituted imidazoles in combination with cheap and abundant iron trichloride hexahydrate. Heterocycles similar to imidazole can be used as ligands in this epoxidation system, too. The novel system is stable towards air and water. It is shown that the mechanism depends strongly on the used ligands and substrates. In the presence of radical scavengers no carbon-centered radical could be detected. [ABSTRACT FROM AUTHOR]

A general synthesis of chiral 4-amino-4,5-dihydro-3H-dinaphthophosphepines 5a–f is described. The resulting monodentate chiral aminophosphinites have been tested in the rhodium-catalyzed asymmetric hydrogenation of methyl α-acetamidocinnamate and methyl α-acetamidoacrylate. Enantioselectivities up to 96% ee were obtained in the presence of 5a and sodium dodecylsulfonate in toluene. [Copyright &y& Elsevier]

A general synthesis of chiral 4,5-dihydro-3H-dinaphthophosphepines 1a–g is described. The resulting ligands represent a new class of monodentate chiral phosphines. First applications of 1a–g in the rhodium-catalyzed asymmetric hydrogenation of unsaturated carboxylic acid derivatives demonstrate the usefulness of our ligands. Enantioselectivities up to 95% ee for the hydrogenation of methyl α-acetamidocinnamate were obtained in the presence of 1d. This result represent the highest enantioselectivity reported for asymmetric hydrogenation in the presence of monodentate phosphines. [Copyright &y& Elsevier]

A series of air‐stable Mn complexes bearing NNS pincer ligands have been synthesized and fully characterized. The activity of the complexes as (transfer) hydrogenation catalysts was investigated in detail, and a variety of ketones (>20 examples) were converted to the corresponding secondary alcohols at room temperature. The synthetic applicability of this class of catalysts is demonstrated by the tolerance of several functional groups including halides, primary amines, nitriles, esters, and nitro‐groups. Moreover, the optimal catalytic system 5c displayed a high chemoselectivity in the presence of other reducible groups such as nitriles, esters, and alkynes. Competitive catalytic experiments with the analogous bidentate NN complex 8 indicated decoordination of the hemilabile thioether‐moiety during formation of the catalytically active hydrido species. [ABSTRACT FROM AUTHOR]

On the way to a green carbon cycle: Ding and co‐workers developed the highly efficient catalyst 1 for the hydrogenation of cyclic carbonates to diols and methanol (TON up to 87 000) by modification of the industrially applied omega process. [ABSTRACT FROM AUTHOR]

A new method for the generation of benzyl radicals from terminal aromatic alkynes has been developed, which allows the direct cross coupling with acrylate derivatives. Our additive-free protocol employs air-stable diamino Mo3S4 cubane-type cluster catalysts in the presence of hydrogen. A sulfur-centered cluster catalysis mechanism for benzyl radical formation is proposed based on catalytic and stoichiometric experiments. The process starts with the cluster hydrogen activation to form a bis(hydrosulfido) [Mo3(μ3-S)(μ-S)(μ-SH)2Cl3(dmen)3]+ intermediate. The reaction of various aromatic terminal alkynes containing different functionalities with a series of acrylates affords the corresponding Giese-type radical addition products. [ABSTRACT FROM AUTHOR]

Several manganese‐PNP pincer catalysts for the formal hydroamination of allylic alcohols are presented. The resulting γ‐amino alcohols are selectively obtained in high yields applying Mn‐1 in a tandem process under mild conditions. [ABSTRACT FROM AUTHOR]

Hydrosilylation reactions, which allow the addition of Si−H to C=C/C≡C bonds, are typically catalyzed by homogeneous noble metal catalysts (Pt, Rh, Ir, and Ru). Although excellent activity and selectivity can be obtained, the price, purification, and metal residues of these precious catalysts are problems in the silicone industry. Thus, a strong interest in more sustainable catalysts and for more economic processes exists. In this respect, recently disclosed hydrosilylations using catalysts based on earth‐abundant transition metals, for example, Fe, Co, Ni, and Mn, and heterogeneous catalysts (supported nanoparticles and single‐atom sites) are noteworthy. This minireview describes the recent advances in this field. [ABSTRACT FROM AUTHOR]

Hydrosilylation reactions, which allow the addition of Si−H to C=C/C≡C bonds, are typically catalyzed by homogeneous noble metal catalysts (Pt, Rh, Ir, and Ru). Although excellent activity and selectivity can be obtained, the price, purification, and metal residues of these precious catalysts are problems in the silicone industry. Thus, a strong interest in more sustainable catalysts and for more economic processes exists. In this respect, recently disclosed hydrosilylations using catalysts based on earth‐abundant transition metals, for example, Fe, Co, Ni, and Mn, and heterogeneous catalysts (supported nanoparticles and single‐atom sites) are noteworthy. This minireview describes the recent advances in this field. [ABSTRACT FROM AUTHOR]

A series of molybdenum(0), (I) and (II) complexes ligated by different PNP and NNN pincer ligands were synthesized and structurally characterized. Along with previously described Mo−PNP complexes Mo‐1 and Mo‐2, all prepared compounds were tested in the catalytic hydrogenation of aromatic nitriles to primary amines. Among the applied catalysts, Mo‐1 is particularly well suited for the hydrogenation of electron‐rich benzonitriles. Additionally, two aliphatic nitriles were transformed into the desired products in 80 and 86 %, respectively. Moreover, catalytic intermediate Mo‐1a was isolated and its role in the catalytic cycle was subsequently demonstrated. [ABSTRACT FROM AUTHOR]

Core–shell nanocatalysts are attractive due to their versatility and stability. Here, we describe cobalt nanoparticles encapsulated within graphitic shells prepared via the pyrolysis of a cationic poly‐ionic liquid (PIL) with a cobalt(II) chloride anion. The resulting material has a core–shell structure that displays excellent activity and selectivity in the self‐dehydrogenation and hetero‐dehydrogenation of primary amines to their corresponding imines. Furthermore, the catalyst exhibits excellent activity in the synthesis of secondary imines from substrates with various reducible functional groups (C=C, C≡C and C≡N) and amino acid derivatives. [ABSTRACT FROM AUTHOR]

Core–shell nanocatalysts are attractive due to their versatility and stability. Here, we describe cobalt nanoparticles encapsulated within graphitic shells prepared via the pyrolysis of a cationic poly‐ionic liquid (PIL) with a cobalt(II) chloride anion. The resulting material has a core–shell structure that displays excellent activity and selectivity in the self‐dehydrogenation and hetero‐dehydrogenation of primary amines to their corresponding imines. Furthermore, the catalyst exhibits excellent activity in the synthesis of secondary imines from substrates with various reducible functional groups (C=C, C≡C and C≡N) and amino acid derivatives. [ABSTRACT FROM AUTHOR]

The development of methods for selective cleavage reactions of thermodynamically stable C−C/C=C bonds in a green manner is a challenging research field which is largely unexplored. Herein, we present a heterogeneous Fe−N−C catalyst with highly dispersed iron centers that allows for the oxidative C−C/C=C bond cleavage of amines, secondary alcohols, ketones, and olefins in the presence of air (O2) and water (H2O). Mechanistic studies reveal the presence of water to be essential for the performance of the Fe−N−C system, boosting the product yield from <1 % to >90 %. Combined spectroscopic characterizations and control experiments suggest the singlet 1O2 and hydroxide species generated from O2 and H2O, respectively, take selectively part in the C−C bond cleavage. The broad applicability (>40 examples) even for complex drugs as well as high activity, selectivity, and durability under comparably mild conditions highlight this unique catalytic system. [ABSTRACT FROM AUTHOR]

The development of methods for selective cleavage reactions of thermodynamically stable C−C/C=C bonds in a green manner is a challenging research field which is largely unexplored. Herein, we present a heterogeneous Fe−N−C catalyst with highly dispersed iron centers that allows for the oxidative C−C/C=C bond cleavage of amines, secondary alcohols, ketones, and olefins in the presence of air (O2) and water (H2O). Mechanistic studies reveal the presence of water to be essential for the performance of the Fe−N−C system, boosting the product yield from <1 % to >90 %. Combined spectroscopic characterizations and control experiments suggest the singlet 1O2 and hydroxide species generated from O2 and H2O, respectively, take selectively part in the C−C bond cleavage. The broad applicability (>40 examples) even for complex drugs as well as high activity, selectivity, and durability under comparably mild conditions highlight this unique catalytic system. [ABSTRACT FROM AUTHOR]

A novel synthetic protocol for the direct oxidation of alkanes, including cyclic and linear ones, to give ketones and alcohols using hydrogen peroxide as terminal oxidant under ambient conditions is presented. The active catalyst for this challenging transformation is conveniently generated by combination of simple Fe salts with N‐methyl bis(picolylamine) (Me‐bpa). Utilizing picolinic acid as additive leads to improved yields of ketones and alcohols (32‐57 %). The reaction can be conveniently scaled up to multi‐g scale. [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]

Density functional theory computations have been carried out to investigate the base free acceptor‐less dehydrogenative coupling of benzyl alcohol to benzyl benzoate catalyzed by defined Mn and Re PNP pincer amido M(CO)2(PNP) and amino HM(CO)2(PNHP) complexes [M = Mn, Re; PNP = N{CH2CH2P(isopropyl)2}2]. Benchmark calculations show that B3PW91 have the best and closest agreement with the experiments than DLPNO‐CCSD(T). Within all proposed elementary steps, the non‐innocent outer‐sphere mechanism incorporating the amido complex and the N–H bond is more kinetically favored than the innocent outer‐sphere mechanism without the amido complex as well as the inner‐sphere mechanism via the de‐coordination of one phosphine ligand to create a vacant site for β‐hydride elimination. The dehydrogenation of hemiacetal to ester represents the rate‐determining step. Both Mn and Re‐based catalysts have close free energy barriers and similar catalytic activity. However, the computed apparent barrier is overestimated on the basis of the experimentally determined TOF for the Mn‐based complexes. DFT calculations help elucidate the mechanism of the base free acceptorless dehydrogenative coupling of benzyl alcohol to benzyl benzoate catalyzed by Mn and Re PNP pincer amido and amino complexes. It was determined that the non‐innocent outer‐sphere mechanism is more favorable than the innocent outer‐sphere and inner‐sphere mechanisms, and the dehydrogenation of hemiacetal to ester represents the rate‐determining step. [ABSTRACT FROM AUTHOR]

The N-alkylation of a variety of primary and secondary amines with a wide range of carboxylic acids is efficiently achieved in the presence of phenylsilane as reducing agent and Karstedt′s Pt catalyst. [ABSTRACT FROM AUTHOR]

A variety of esters is reduced for the first time selectively using an iridium pincer-type complex as catalyst. [ABSTRACT FROM AUTHOR]