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Chiral amines can be made by insertion of a carbene into an N–H bond using two-catalyst systems that combine a transition metal-based carbene-transfer catalyst and a chiral proton-transfer catalyst to enforce stereocontrol. Haem proteins can effect carbene N–H insertion, but asymmetric protonation in an active site replete with proton sources is challenging. Here we describe engineered cytochrome P450 enzymes that catalyse carbene N–H insertion to prepare biologically relevant α-amino lactones with high activity and enantioselectivity (up to 32,100 total turnovers, >99% yield and 98% e.e.). These enzymes serve as dual-function catalysts, inducing carbene transfer and promoting the subsequent proton transfer with excellent stereoselectivity in a single active site. Computational studies uncover the detailed mechanism of this new-to-nature enzymatic reaction and explain how active-site residues accelerate this transformation and provide stereocontrol. A haem protein that serves as a dual-function catalyst capable of inserting a carbene into a N–H bond to form α-amino lactones has been reported. The enzyme catalyses both carbene transfer and the subsequent proton transfer in a single active site. This transformation can proceed at the gram scale with high efficiency and enantioselective control.

trans-Dichloropalladium(II) complexes with amino acid esters PdCl2L2 have been synthesized via selective hydrolytic cleavage of the nitrogen–carbon bond in 1,3,5-tris(ethoxycarbonylmethyl)- and 1,3,5-tris[(S)-1′(methoxycarbonyl)ethyl]-1,3,5-triazinane under the action of palladium(II) in methanol or in water–acetone mixture. The nucleophilic attack of water or methanol results in selective cleavage of the 1,3,5-triazinane ring in the complexes of palladium(II) with the starting triazinanes, affording the dichloropalladium(II) complexes with amino acids esters.

Carbon-nitrogen bond activation, via uranyl photoredox catalysis with water, enabled the conversion of 40 protogenetic anilines, 8 N-substituted anilines and 9 aniline-containing natural products/pharmaceuticals to the corresponding phenols in an ambient environment. A single-electron transfer process between a protonated aniline and uranyl catalyst, which was disclosed by radical quenching experiments and Stern-Volmer analysis, facilitated the following oxygen atom transfer process between the radical cation of protonated anilines and uranyl peroxide originating from water-splitting. 18O labeling and 15N tracking unambiguously depicted that the oxygen came from water and amino group left as ammonium salt. The 100-fold efficiency of the flow operation demonstrated the great potential of the conversion process for industrial synthetic application.

A practical catalytic asymmetric benzylic C(sp3)–H amination through the intermolecular insertion of a rhodium-bound nitrene species is reported. The reaction of various substrates (used as the lim...

International audience; Several catalytic reactions such as Ullmann, Chan–Lam, Huisgen 1,3-dipolar cycloaddition, [2 + 3] cycloaddition, condensation, and coupling reactions under suitable conditions have been used for the synthesis of fundamental structures containing a carbon–nitrogen (C–N) bond. Graphene oxide (GO) and its derivatives as heterogeneous catalysts have attracted considerable attention for the synthesis of organic building blocks. Loading of GO derivatives with copper complexes or nanoparticles, as one of the most abundant and low toxic transition metals, allowed to design new composites with predominant ability to C–N bond formation. In this review article, we present a comprehensive overview on the synthesis of building blocks containing a C–N bond such as amines, triazoles, tetrazoles, propargyl amines, imidazoles, and benzodiazepines using GO derivatives loaded with copper complexes or nanoparticles. © 2021 John Wiley and Sons, Ltd.

Luzopeptins and related decadepsipeptides are bisintercalator nonribosomal peptides featuring rare acyl-substituted tetrahydropyridazine-3-carboxylic acid (Thp) subunits that are critical to their biological activities. Herein, we reconstitute the biosynthetic tailoring pathway in luzopeptin A biosynthesis through in vivo genetic and in vitro biochemical approaches. Significantly, we revealed a multitasking cytochrome P450 enzyme that catalyzes four consecutive oxidations including the highly unusual carbon-nitrogen bond desaturation, forming the hydrazone-bearing 4-OH-Thp residues. Moreover, we identified a membrane-bound acyltransferase that likely mediates the subsequent O-acetylation extracellularly, as a potential self-protective strategy for the producer strain. Further genome mining of novel decadepsipeptides and an associated P450 enzyme have provided mechanistic insights into the P450-mediated carbon-nitrogen bond desaturation. Our results not only reveal the molecular basis of pharmacophore formation in bisintercalator decadepsipeptides, but also expand the catalytic versatility of P450 family enzymes.

Self-assembled multilayer iron(0) nanoparticles (NPs, 6-10 nm), namely, sulfur-modified Au-supported Fe(0) [SAFe(0)], were developed for ligand-free one-pot carbon-carbon/carbon-nitrogen bond-forming reactions. SAFe(0) was successfully prepared using a well-established metal-nanoparticle catalyst preparative protocol by simultaneous in situ metal NP and nanospace organization (PSSO) with 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (Si-DHP) as a strong reducing agent. SAFe(0) was easy to handle in air and could be recycled with a low iron-leaching rate in reaction cycles.

Palladium-catalyzed Suzuki–Miyaura cross-coupling or aryl halides is widely employed in the synthesis of many important molecules in synthetic chemistry, including pharmaceuticals, polymers and functional materials. Herein, we disclose the first palladium-catalyzed decarbonylative Suzuki–Miyaura cross-coupling of amides for the synthesis of biaryls through the selective activation of the N–C(O) bond of amides. This new method relies on the precise sequence engineering of the catalytic cycle, wherein decarbonylation occurs prior to the transmetallation step. The reaction is compatible with a wide range of boronic acids and amides, providing valuable biaryls in high yields (>60 examples). DFT studies support a mechanism involving oxidative addition, decarbonylation and transmetallation and provide insight into high N–C(O) bond activation selectivity. Most crucially, the reaction establishes the use of palladium catalysis in the biaryl Suzuki–Miyaura cross-coupling of the amide bond and should enable the design of a wide variety of cross-coupling methods in which palladium rivals the traditional biaryl synthesis from aryl halides and pseudohalides.

We report the Pd-catalyzed acyl and the Ni-catalyzed biaryl Suzuki–Miyaura cross-coupling of N-acetyl-amides with arylboronic acids by selective N–C(O) cleavage. Activation of the amide bond by N-acylation provides electronically destabilized, acyclic, nonplanar amide, which readily undergoes cross-coupling with a wide range of boronic acids to produce biaryl ketones or biaryls in a highly efficient manner. Most crucially, the presented results introduce N-acetyl-amides as reactive acyclic amides in the emerging manifold of transition-metal-catalyzed amide cross-coupling. The scope and origin of high selectivity are discussed. Mechanistic studies point to remodeling of amidic resonance and amide bond twist as selectivity determining features in a unified strategy for cross-coupling of acyclic amides. Structural studies, mechanistic investigations as well as beneficial effects of the N-acyl substitution on cross-coupling of amides are reported.

Main driving force of this research work is to focus 9th principle (Catalysis) out of 12 principles of green chemistry so as to protect environment concerned with the reduction in generation of carbon dioxide, one of the green house gas. An innovative development of chemical pathway regarding N-alkylation reaction carried out by adding and recycling only catalytic amount of Hydrotalcite as solid base instead of stoichiometric amount, as per prior art techniques, has attempted. Synthesis of 3° amines, important Active Pharmaceutical Ingredients (APIs) and their intermediates, maintaining the same quality attributes resulting in to minimum generation of carbon dioxide are described. These concept is designed, synthesized, characterized, quantified and compared using “Carbon Efficiency”, a Green Chemistry Metrics, with already reported work to prove its sustainability. It is industrially advantageous by getting improvement in carbon efficiency and yield as outcome. Here we show a practical greener approach towards Carbon – Nitrogen bond formation with the help of calculation of Carbon efficiency and rate of reaction for first time.

A catalytic method to synthesize 1,3,-dienes from propargylic precursors is reported. This palladium-catalyzed carbon-nitrogen bond-forming reaction furnishes 2-amino-1,3-dienes in excellent yields (up to 98%) and shows a broad tolerance to functional group diversity. The reaction has been demonstrated for over 30 amine substrates, including anilines and indoles, and proceeds under mild neutral conditions. The resulting 1,3-dienes are of great synthetic interest because of their further reaction potential.

A new cross-coupling reaction of N-benzylic sulfonamides with 2-substituted cyanoacetates for the synthesis of 2-substituted benzylbenzene was reported. In the presence of AlCl3, a broad range of N-benzylic sulfonamides reacted smoothly with 2-substituted cyanoacetates to afford structurally diverse benzylbenzenes in moderate to excellent yields. The conversion could be enlarged to gram-scale efficiently. The practicability of this approach was further manifested in the synthesis of a related bioactive agent with high anti-inflammatory activity.

Reactions of CuCl, CuCl2 and CuBr2 with 1,3,5-tri-tert-butyl-1,3,5-triazacyclohexane (tBu3tach) resulted in the formation of [(tBu3tach-H)+(CuCl2)] (1), [(tBu3tach)(CuCl2)] (2) and [(tBu3tach-H)+(CuBr2)] (3) respectively. Interestingly, CuBr was found to mediate the cleavage of the C–N bonds of tBu3tach in a vast range of solvents, namely, chloroform, dichloromethane, tetrahydrofuran, acetonitrile and methanol to yield [Cu4Br4(tBuNCH2)4] (4) and stands as an example of C–N bond cleavage of 1,3,5-triazacyclohexane rings by copper salts. Compounds 1 and 3 contains amidinium cations and are unstable in solution towards the release of copper. The release of copper from 3 in solution was confirmed by the isolation of the compound, [CuBr(MeCN)] (5). Formation of the amidinium cations [(tBu3tach-H)+] in 1 and 3 may be avoided by the use of PPh3 to yield [(tBu3tach)Cu(PPh3)](PF6) (6), while the coordinated N-tert-butylmethanimine (tBuNCH2) in 4 could be replaced by PPh3 to yield [Cu4Br4(PPh3)4] (7). Complexes 1–7 are characterized by a combination of single crystal X-ray structure determination and/or elemental analysis, NMR, IR, and UV–Vis spectroscopy, and Mass spectrometry.

A green reaction medium has been developed from the Water Extract of Teak leaf (Tectona grandis) ash (WET). The alkaline nature of the WET was successfully applied towards hydration of nitriles, conversion of arylboronic acids to phenols with 30% aqueous H2O2, Knoevenagel condensation for benzylidenemalononitrile derivatives formation and Chan-Lam reaction of arylboronic acids with imidazole derivatives. In current protocols dual role of WET as reaction medium as well as base has been explored. A wide range of substrates with varying electronic natures is compatible under these WET mediated reaction conditions with excellent yields.

A DABCO-catalyzed annulation reaction of pyridin-2-amine and substituted allenoates has been disclosed. This strategy allows for the ring-opening of a pyridine ring system and the formation of two new rings including a pyrimidinone ring and a benzene ring in an efficient manner.

Intramolecular carbon–nitrogen bond formation between a carbonyl and proximal azopyridine ligand by ligand-based reduction led to the formation of a novel ruthenium complex containing a bidentate carbamoyl ligand. Reversible C–N bond formation and cleavage reactions were confirmed by chemical and electrochemical redox reactions. The change in character of the CO moiety based on intramolecular structural change affects the CO ligand photoreactivity. The molecular structures of the carbamoyl compound and photoreaction products were determined by X-ray crystallography to confirm the present photoreaction process.

An efficient strategy is developed for chemical recycling of cured epoxy resin (CEP) from its carbon fiber reinforced polymer composites (CFREP) using AlCl3/CH3COOH as the degradation system. Acetic acid swells the dense structures of CEP, facilitating the penetration of the aluminum ion catalyst into the polymer matrix. The weakly coordinating aluminum ions in CH3COOH solution selectively cleave the C–N bond while leaving the C–C, C–O (aryl alkyl ether) bonds intact. This process recovers valuable oligomers and carbon fibers from CFREP.

Carbon–nitrogen bond-forming cross-coupling reaction of haloarenes with N-trimethylsilyl (TMS)-substituted secondary and primary arylamines proceeded with the aid of a palladium catalyst and a fluo...

New carbon-nitrogen bonds were formed on addition of isocyanide and ketone reagents to the oxonitride species [{Ti(η(5)-C5Me5)(μ-O)}3(μ3-N)] (1). Reaction of 1 with XylNC (Xyl = 2,6-Me2C6H3) in a 1:3 molar ratio at room temperature leads to compound [{Ti(η(5)-C5Me5)(μ-O)}3(μ-XylNCCNXyl)(NCNXyl)] (2), after the addition of the nitrido group to one coordinated isocyanide and the carbon-carbon coupling of the other two isocyanide molecules have taken place. Thermolysis of 2 gives [{Ti(η(5)-C5Me5)(μ-O)}3(XylNCNXyl)(CN)] (3) where the heterocumulene [XylNCCNXyl] moiety and the carbodiimido [NCNXyl] fragment in 2 have undergone net transformations. Similarly, tert-butyl isocyanide (tBuNC) reacts with the starting material 1 under mild conditions to give the paramagnetic derivative [{Ti3(η(5)-C5Me5)3(μ-O)3(NCNtBu)}2(μ-CN)2] (4). However, compound 1 provides the oxo ketimide derivatives [{Ti3(η(5)-C5Me5)3(μ-O)4}(NCRPh)] [R = Ph (5), p-Me(C6H4) (6), o-Me(C6H4) (7)] upon reaction with benzophenone, p-methylbenzophenone, and o-methylbenzophenone, respectively. In these reactions, the carbon-oxygen double bond is completely ruptured, leading to the formation of a carbon-nitrogen and two metal-oxygen bonds. The molecular structures of complexes 2-4, 6, and 7 were determined by single-crystal X-ray diffraction analyses. Density functional theory calculations were performed on the incorporation of isocyanides and ketones to the model complex [{Ti(η(5)-C5H5)(μ-O)}3(μ3-N)] (1H). The mechanism involves the coordination of the substrates to one of the titanium metal centers, followed by an isomerization to place those substrates cis with respect to the apical nitrogen of 1H, where carbon-nitrogen bond formation occurs with a low-energy barrier. In the case of aryl isocyanides, the resulting complex incorporates additional isocyanide molecules leading to a carbon-carbon coupling. With ketones, the high oxophilicity of titanium promotes the unusual total cleavage of the carbon-oxygen double bond.

The carbon-nitrogen bond of β-lactams is cleaved by palladium(0), and an alkene is intramolecularly inserted therein. The following reductive elimination produces nitrogen-containing benzo-fused tricycles in good to high yields.

Upon reaction with KBEt3H, the pseudo tetrahedral Fe(II) complex 5 with a bulky enamido-phosphazide ligand set undergoes elimination of N2 and 1,3-Me2C6H4 to generate the dinuclear Fe(II) derivative 6 with bridging phosphinimido units. When the reaction is performed using KBEt3D, no deuterium is incorporated into the eliminated 1,3-Me2C6H4; all of the deuterium ends up as D2. When the reaction is performed in THF-d8, only 2-d-1,3-Me2C6H3D was detected by GCMS. These studies are consistent with a radical mechanism.

A vanadium catalyzed 1,3-rearrarngement of allenols to form transient vanadium enolates that selectively couple with electrophilic nitrogen sources is reported even in the presence of competing simple protonation and Alder-ene pathways. The hydrazine products can be cyclized in a 6-endo-trig fashion which, upon reductive cleavage of the N-N bond, yield 1,4-diamines. Additionally, cleavage of the N-N bond before cyclization can be achieved to form β-hydroxy amines, a common structural motif of biologically active compounds.

Carbon-nitrogen bonds are ubiquitous in organic chemistry. This review focuses on the formation of these important linkages and describes some recent advances in redox reactions that involve elemental sulfur and molecular iodine as excellent reagents and catalysts.

Over the past few decades, researchers have made substantial progress in the development of transition metal complexes that activate and functionalize C-H bonds. For the most part, chemists have focused on aliphatic and aromatic C-H bonds and have put less effort into complexes that activate and functionalize vinylic C-H bonds. Our groups have recently developed a novel method to functionalize vinylic C-H bonds that takes advantage of the unique ligand-based reactivity of a rare class of metal dinitrosyl complexes. In this Account, we compare and discuss the chemistry of cobalt and ruthenium dinitrosyl complexes, emphasizing alkene binding, C-H functionalization, and catalysis. Initially discovered in the early 1970s by Brunner and studied more extensively in the 1980s by the Bergman group, the cyclopentadienylcobalt dinitrosyl complex CpCo(NO)2 reacts reversibly with alkenes to give, in many cases, stable and isolable cobalt dinitrosoalkane complexes. More recently, we found that treatment with strong bases, such as lithium hexamethyldisilazide, Verkade's base, and phosphazene bases, deprotonates these complexes and renders them nucleophilic at the carbon α to the nitroso group. This conjugate anion of metal dinitrosoalkanes can participate in conjugate addition to Michael acceptors to form new carbon-carbon bonds. These functionalized cobalt complexes can further react through alkene exchange to furnish the overall vinylic C-H functionalized organic product. This stepwise sequence of alkene binding, functionalization, and retrocycloaddition represents an overall vinylic C-H functionalization reaction of simple alkenes and does not require directing groups. We have also developed an asymmetric variant of this reaction sequence and have used this method to synthesize C1- and C2-symmetric diene ligands with high enantioinduction. Building upon these stepwise reactions, we eventually developed a simple one-pot procedure that uses stoichiometric amounts of a cobalt dinitrosoalkane complex for both inter- and intramolecular C-H functionalization. We can achieve catalysis in one-pot intramolecular reactions with a limited range of substrates. Our groups have also reported an analogous ruthenium dinitrosyl complex. In analogy to the cobalt complex, this ruthenium complex reacts with alkenes in the presence of neutral bidentate ligands, such as TMEDA, to give octahedral dinitrosoalkane complexes. Intramolecular functionalization or cyclization of numerous ruthenium dinitrosoalkane complexes proceeds under mild reaction conditions to give the functionalized organic products in excellent yields. However, despite extensive efforts, so far we have not been able to carry out intermolecular reactions of these complexes with a variety of electrophiles or C-H functionalization reactions. Although additional work is necessary to further boost the catalytic capabilities of both cobalt and ruthenium dinitrosyl complexes for vinylic C-H functionalization of simple alkenes, we believe this ligand-based vinylic C-H functionalization reaction has provided chemists with a useful set of tools for organic synthesis.

There are many methods available in the synthetic toolbox to construct carbon–nitrogen bonds, but these standardly require preactivation of the substrate. These involve classical, nonmetal catalyzed methods (e.g., nucleophilic substitutions) and catalytic methods (e.g., the Ullmann condensation reaction) as well as modern metal-catalyzed approaches with wide scope (Buchwald–Hartwig reaction, hydrogen-borrowing reactions). Cross-dehydrogenative couplings (CDCs) couple a C–H with an N–H bond and do not require any preactivation and are therefore considered the “nec plus ultra” in amination chemistry. Based on the ubiquitous nature of C–H bonds in substrates and the wide availability of amines as reactants they inherently show great application potential. Especially from a sustainable chemistry point of view it holds great promise, provided green oxidants can be used in a safe manner. However, though major advances have been made in the field, this last addition to the carbon–nitrogen bond forming toolbox is still in its infancy. The major investigations and advances dealing with CDCs for C–N bond formation since 2014 are summarized in this review. Intra- and intermolecular direct oxidative amination reactions on C(sp 2 )–H as well as C(sp 3 )–H bonds are included. Both metal-catalyzed and metal-free approaches are covered, as well as the corresponding mechanistic proposals.

The first Negishi cross-coupling of amides for the synthesis of versatile diaryl ketones by selective C−N bond activation under exceedingly mild conditions is reported. The cross-coupling was accomplished with bench-stable, inexpensive precatalyst [Ni(PPh3)2Cl2] that shows high functional-group tolerance and enables the synthesis of highly functionalized diaryl ketone motifs. The coupling occurred with excellent chemoselectivity favoring the ketone (cf. biaryl) products. Notably, this process represents the mildest conditions for amide N−C bond activation accomplished to date (room temperature

International audience; Actinide complexes demonstrate unparalleled reactivity towards small molecules. However, utilizing these powerful transformations in a predictable and deliberate manner remains challenging. Therefore, developing actinide systems that not only perform noteworthy chemistry but also demonstrate controllable reactivity is a key goal. We describe a bis(NHC)borate thorium‐bpy complex (1) that is capable of reductively cleaving the R−NC bond in a series of organic isocyanides. In contrast to most actinide‐mediated bond activations, the dealkylation event mediated by 1 is remarkably general and yields very well‐defined products that assist in mechanistic elucidation. Synthesis of the rearranged but‐3‐enyl product from the reaction of 1 and cyclopropylmethyl isocyanide supports the notion of a radical‐based mechanism.

The use of tert-butanesulfinamides as nitrogen nucleophiles in carbon-nitrogen bond forming reactions is reviewed. This field has grown in the shadow of the general interest in N-tert-butanesulfinyl imines for asymmetric synthesis and occupies now an important place in its own right in the chemistry of the chiral amine reagent tert-butanesulfinamide. This article provides an overview of the area and emphasizes recent contributions wherein the tert-butanesulfinamides act as chiral auxiliaries or perform as nitrogen donors in metal-catalyzed amination reactions.

The first Ni-catalyzed Suzuki-Miyaura coupling of amides for the synthesis of widely occurring biaryl compounds through N-C amide bond activation is reported. The reaction tolerates a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents on both coupling partners. The reaction constitutes the first example of the Ni-catalyzed generation of aryl electrophiles from bench-stable amides with potential applications for a broad range of organometallic reactions.

Oxidative dearomatization of N-tosylated anilines and subsequent reaction with cyanoacetates and related cyano substituted activated methylene compounds followed by the addition of an external nucleophile offers a straightforward access to arenes substituted with a quarternary carbon.

The first Ni-catalyzed Suzuki-Miyaura coupling of amides for the synthesis of widely occurring biaryl compounds through N-C amide bond activation is reported. The reaction tolerates a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents on both coupling partners. The reaction constitutes the first example of the Ni-catalyzed generation of aryl electrophiles from bench-stable amides with potential applications for a broad range of organometallic reactions.

Gas-phase electron diffraction experiments show that the C–N bond in aniline (1.407 A) is significantly shorter than in nitrobenzene (1.486 A). It is known that the amino group is electron-donating and the nitro group is electron-withdrawing, and both substitution groups can effectively conjugate with benzene. Thus, it is puzzling why the C–N bond in nitrobenzene is even longer than the single C–N bond in methylamine (1.472 A). In this work, we performed computations by strictly localizing the π electrons with the block-localized wavefunction (BLW) method, which is a variant of ab initio valence bond theory. Geometry optimizations of electron-localized states, where the conjugation over the C–N bond is quenched, show that the conjugation in nitrobenzene is only half of the conjugation in aniline. But even in optimal electron-localized states, the C–N bond in nitrobenzene is still 0.074 A longer than in aniline. As a consequence, it is indeed not the π conjugation which is responsible for the disparity of the C–N bond distances in these systems. Instead, we demonstrated that the π–π repulsion, which is contributed by both Pauli exchange and electrostatic interaction, plays the key role in this “abnormal” behavior. Notably, the π resonance within the nitro group generates a considerable dipole, which repels the π electrons in the benzene ring. The deactivation of the resonance within the nitro group significantly shortens the C–N bond by 0.06 A. The unfavorable π–π electrostatic repulsion is further exemplified by N2O4. In fact, the destabilizing π–π repulsion is ubiquitous but largely neglected in conjugated systems where only the stabilizing conjugation is the focus. Experimental phenomena such as the C–N bond distances in aniline and nitrobenzene result from the balance of both stabilizing and destabilizing forces.

An efficient method for carbon–nitrogen bond formation between ally silyl ethers and N,N-acyltosylhydrazine was developed under very mild conditions using 2 mol% of mercuric triflate [Hg(OTf)2] as a catalyst. This method does not require the use of any ligand system or supplementary additives and is applicable to the preparation of various N-allylhydrazides with good to excellent yields.

The metal coordination complex K4[Fe(CN)6] is an efficient and environmentally benign catalyst for the synthesis of imidazolines and benzimidazoles from various aldehydes and 1,2-diamines in aqueous medium at room temperature. This protocol gives excellent yield of product with desired purity.

Imination and amidation of sulfides, sulfoxides, and olefins using 4H-1,2,4-triazole-4-amine as a nitrogen source with PhI(OAc)2 as an oxidant were achieved in moderate to high yields without the addition of a catalyst. The carbon–nitrogen and sulfur–nitrogen bond forming reactivity is consistent with a nitrene insertion mechanism in which the reactivity generally increases with decreasing N–H bond dissociation energy of the nitrogen source and increasing oxidation potential of the oxidant.

Heating [WO 2 (S 2 CNBu i 2 ) 2 ] with a slight excess of ArNCO (Ar = Ph, p-tolyl) results in the rapid formation of imido-ureato complexes [W(NAr){κ 2 -ArNC(O)NAr}(S 2 CNBu i 2 ) 2 ], a transformation believed to occur via the bis(imido) intermediates [W(NAr) 2 (S 2 CNBu i 2 ) 2 ]. The ureato ligand is easily removed (as the urea) upon addition of gaseous HCl to afford the dichloride [W(NAr)Cl 2 (S 2 CNBu i 2 ) 2 ]. While bis(imido) complexes are unavailable from the direct reaction of isocyanates (or amines) with [WO 2 (S 2 CNBu i 2 ) 2 ], they can be prepared upon addition of dithiocarbamate salts to [W(NBu t ) 2 (NHBu t ) 2 ] addition of two equivalents of [NH 2 Bu i 2 ][Bu i 2 NCS 2 ] affording [W(NBu t ) 2 (S 2 CNBu i 2 ) 2 ] in which both imido groups are linear.

A range of ketones and aldehydes smoothly undergo asymmetric S(N)1 α-alkylation with N-benzylic sulfonamides in the presence of 10 mol % of a chiral imidazolidinone and trifluoroacetic acid to give the corresponding products in good to excellent yields and with good enantioselectivity. This chemistry has been successfully extended to the asymmetric desymmetrization of 4-substituted cyclohexanones, which exhibits greater than 99:1 diastereoselectivity and good enantioselectivity.

A palladium-catalyzed carbonation-diketonization reaction of terminal alkenes via carbon-nitrogen bond cleavage under an atmosphere of oxygen has been developed. A series of 1,2-diketones were readily prepared from the reaction of aromatic terminal alkenes with nitroalkanes.