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The given text provides information about the synthesis and characterization of various compounds. The compounds were prepared using a general procedure and purified by flash chromatography. The yield, physical properties, and spectroscopic data of each compound are provided. The compounds synthesized include N-Cyclohexyl-N-methyl-4-((3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-7-yl)oxy)butanamide, 6-Methyl-2H-benzo[b][1,4]oxazin-3(4H)-one, 6-Ethyl-2H-benzo[b][1,4]oxazin-3(4H)-one, 6-Propyl-2H-benzo[b][1,4]oxazin-3(4H)-one, 6-Methoxy-2H-benzo[b][1,4]oxazin-3(4H)-one, 1-Oxa-4-azaspiro[4.5]deca-6,9-diene-3,8-dione, 7-Fluoro-2H-benzo[b][1,4]oxazin-3(4H)-one, and 6-Fluoro-2H-benzo[b][1,4]oxazin-3(4H)-one. [Extracted from the article]

Catalytic C−N bond formation by direct activation of C−H bonds offers wide synthetic potential. En route to C−H amination, complexes with organic azides are critical precursors towards the reactive nitrene intermediate. Despite their relevance, α‐N coordinated organoazide complexes are scarce in general, and elusive with iron, although iron complexes are by far the most active catalysts for C−H amination with organoazides. Herein, we report the synthesis of a stable iron α‐N coordinated organoazide complex from [Fe(N(SiMe3)2)2] and AdN3 (Ad=1‐adamantyl) and its crystallographic, IR, NMR and zero‐field 57Fe Mössbauer spectroscopic characterization. These analyses revealed that the organoazide is in fast equilibrium between the free and coordinated state (Keq=62). Photo‐crystallography experiments showed gradual dissociation of N2, which imparted an Fe−N bond shortening and correspond to structural snapshots of the formation of an iron imido/nitrene complex. Reactivity of the organoazide complex in solution showed complete loss of N2, and subsequent formation of a C−H aminated product via nitrene insertion into a C−H bond of the N(SiMe3)2 ligand. Monitoring this reaction by 1H NMR spectroscopy indicates the transient formation of the imido/nitrene intermediate, which was supported by Mössbauer spectroscopy in frozen solution. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Enantioselective or enantioconvergent iron‐catalyzed ring‐closing C(sp3)‐H aminations of N‐aroyloxyurea through intermediate iron nitrene species provide chiral 2‐imidazolidinones in up to 99% yield and with up to 95% ee (40 examples). This is a rare example in which sustainable iron catalysis is combined with C(sp3)‐H amination and asymmetric catalysis. Chiral 2‐imidazolidinones are prevalent structural motifs in bioactive molecules and can also be hydrolyzed to valuable chiral vicinal diamines in a single step. [ABSTRACT FROM AUTHOR]

An account of our development of reactions to construct N -heterocycles by triggering cyclization–migration tandem reactions from aryl azides, nitroarenes, and aryl amines is described. The reactivity patterns of metal N -aryl nitrenes, nitrosoarenes, N -aryl nitrogen radical anions, and N -aryl nitrenoids are compared. 1 Introduction 2 Unlocking the Reactivity Embedded in Aryl Azides 3 Exploiting the Reactivity of Nitrosoarenes Generated from Nitroarenes 4 Radical Anion N -Aryl Nitrogen Reactive Intermediates from Nitroarenes 5 Oxidation of Aryl Amines to Access Electrophilic N -Aryl Nitrenoids 6 Conclusion [ABSTRACT FROM AUTHOR]

Photochemical, metal‐free nitrene transfer reactions for C−H amination, aziridination, or sulfilimination are highly desirable. Yet, photochemical sulfilimination reactions of nitrenes with sulfides are underdeveloped as singlet nitrene species would be required for a productive reaction. Herein, we describe the blue‐light‐mediated sulfilimination reaction using iminoiodinanes. We developed a protocol for a highly efficient stoichiometric reaction, which allows for the synthesis of sulfilimines in only 10 minutes reaction time. We further applied our reaction procedure towards allyl sulfides for the synthesis of sulfenamides in a sulfilimination/rearrangement cascade reaction. Moreover, we performed computational calculations and uncovered the participation of a singlet nitrene intermediate, which rapidly reacts with methyl phenyl sulfide to give the desired product. [ABSTRACT FROM AUTHOR]

C−H amination and amidation by catalytic nitrene transfer are well‐established and typically proceed via electrophilic attack of nitrenoid intermediates. In contrast, the insertion of (formal) terminal nitride ligands into C−H bonds is much less developed and catalytic nitrogen atom transfer remains unknown. We here report the synthesis of a formal terminal nitride complex of palladium. Photocrystallographic, magnetic, and computational characterization support the assignment as an authentic metallonitrene (Pd−N) with a diradical nitrogen ligand that is singly bonded to PdII. Despite the subvalent nitrene character, selective C−H insertion with aldehydes follows nucleophilic selectivity. Transamidation of the benzamide product is enabled by reaction with N3SiMe3. Based on these results, a photocatalytic protocol for aldehyde C−H trimethylsilylamidation was developed that exhibits inverted, nucleophilic selectivity as compared to typical nitrene transfer catalysis. This first example of catalytic C−H nitrogen atom transfer offers facile access to primary amides after deprotection. [ABSTRACT FROM AUTHOR]

A stereoselective amination of thioethers to access sulfilimines using N‐mesyloxycarbamates in a catalytic system composed of iron chloride (II) and a pyridine oxazoline (PyOX) ligand, has been developed. The reaction proceeds with modest to good yields and selectivities (up to 86 : 14 d.r. and 72 : 28 e.r.). Selectivity was controlled by both the structure of the chiral ligand and the amination reagent. [ABSTRACT FROM AUTHOR]

Copper nitrene complexes are highly reactive species and are known as intermediates in the copper catalyzed C–H amination. In this study, three novel copper tosyl nitrene complexes were synthesized at low temperatures, stabilized with heteroscorpionate ligands of the bis(pyrazolyl)methane family. The copper nitrenes were obtained by the reaction of a copper(I) acetonitrile complex with SPhINTs in dichloromethane. We show that the ligand design has a major influence on the catalytic activity and the thermal stability of the copper nitrene complex. Not only the choice of the third N donor, but also the substituent in the 5-position of the pyrazolyl moiety, have an impact on the stability. Furthermore, the novel copper nitrene complexes were used for catalytic aziridination of styrenes and C–H amination reactions of aromatic and aliphatic substrates under mild reaction conditions. Even challenging substrates like benzene and cyclohexane were aminated with good yields. The copper nitrene complexes were characterized using UV/Vis spectroscopy, low temperature Evans NMR spectroscopy, density functional theory, domain-based local pair natural orbital coupled cluster calculations (DLPNO-CCSD(T)) and cryo-UHR mass spectrometry. [ABSTRACT FROM AUTHOR]

A set of new guaianolide derivatives (1–9) was obtained from ludartin, achalensolide, and 11,13‐dihydroachalensolide by application of catalytic nitrene transfer reactions. Intermolecular nitrene C(sp3)−H insertions led to the amination of C‐1, C‐2, and C‐10 positions, while alkene aziridination was also observed under these reaction conditions. The antiproliferative activity of natural compounds and their derivatives was evaluated against a panel of human solid tumor cell lines. The results show that an increase in the biological activity was observed following amination at the C‐2 position of Ludartin, thereby demonstrating the interest in late‐stage C−H amination to improve the bioactivity of natural products. [ABSTRACT FROM AUTHOR]

A dirhodium-catalyzed, β-selective C–H amination of organosilicon compounds has been developed. Primary C(sp3)–H bonds of silylethyl groups and secondary C(sp3)–H bonds of silacycloalkanes can be selectively converted to C–N bonds at the β-position of the silicon atoms. The experimental data and theoretical calculations indicate that the strong σ-donor ability of the carbon–silicon bonds is responsible for the β-selectivity. Kinetic isotope effects clearly demonstrate that the C–H bond cleavage step is not turnover-limiting, but selectivity-determining. [ABSTRACT FROM AUTHOR]

C–H bonds are ubiquitous and abundant in organic molecules. If C–H bonds could be directly converted to desired functional groups in a chemo‐, site‐, and stereoselective manner, C–H functionalization would be a strong and useful tool for organic synthesis. Recent developments in catalytic and enzymatic chemistry have achieved highly sustainable and selective nitrene C–H insertion. Initially, C–H amination was inspired by model studies on enzymatic oxidation and used iminoiodinanes, nitrogen analogs of iodosobenzene, as nitrene precursors. Transition‐metal/iminoiodinane systems are well studied and established. These systems can directly introduce sulfonamide groups with excellent stereoselectivity, albeit with co‐production of iodobenzene as waste material. Fortunately, the atom economics of this methodology were improved by introducing highly sustainable nitrene sources such as azide compounds and 1,2,4‐dioxazol‐5‐one derivatives. In this review, we present the details of these developments with respect to their catalysts and nitrene sources. [ABSTRACT FROM AUTHOR]

Terminal copper-nitrenoid complexes have inspired interest in their fundamental bonding structures as well as their putative intermediacy in catalytic nitrene-transfer reactions. Here, we report that aryl azides react with a copper(I) dinitrogen complex bearing a sterically encumbered dipyrrin ligand to produce terminal copper nitrene complexes with near-linear, short copper–nitrenoid bonds [1.745(2) to 1.759(2) angstroms]. X-ray absorption spectroscopy and quantum chemistry calculations reveal a predominantly triplet nitrene adduct bound to copper(I), as opposed to copper(II) or copper(III) assignments, indicating the absence of a copper−nitrogen multiple-bond character. Employing electron-deficient aryl azides renders the copper nitrene species competent for alkane amination and alkene aziridination, lending further credence to the intermediacy of this species in proposed nitrene-transfer mechanisms. [ABSTRACT FROM AUTHOR]

The past few decades have witnessed extensive efforts to disclose the unique reactivity of metal–nitrenes, because they could be a powerful synthetic tool for introducing the amine functionality into unactivated chemical bonds. The reactivity of metal–nitrenes, however, is currently mainly confined to aziridination (an insertion into a C=C bond) and C−H amination (an insertion into a C−H bond). Nitrene insertion into an amide C−N bond, however, has not been reported so far. In this work we have developed a rhodium‐catalyzed one‐nitrogen insertion into amide C−N and sulfonamide S−N bonds. Experimental and theoretical analyses based on density functional theory indicate that the formal amide insertion proceeds via a rhodium‐coordinated ammonium ylide formed between the nitrene and the amide nitrogen, followed by acyl group transfer concomitant with C−N bond cleavage. Mechanistic studies have allowed rationalization of the origin of the chemoselectivity observed between the C−H and amide insertion reactions. The methodology presented herein is the first example of an insertion of nitrene into amide bonds and provides facile access to unique diazacyclic systems with an N−N bond linkage. Novel nitrene insertion. An intramolecular insertion reaction of Rh–nitrene into amide C−N and sulfonamide S−N bonds has been developed (see figure) via the unprecedented formation of an N+−N− ylide from the Rh–nitrene and the amide nitrogen. Experimental and theoretical analyses of the reaction mechanism have also been conducted and support the ylide pathway. [ABSTRACT FROM AUTHOR]

An intermolecular nitrene insertion catalyzed by heterobimetallic Co−Pd complexes is reported herein. In a previous report, paddlewheel complex CoPd(OAc)4 was found to have similar reactivity with the well‐known catalyst, Rh2(OAc)4 in the intramolecular C−H amination. For the more challenging intermolecular reaction, biscarboxylate ligand esp acid was used for the Co−Pd core. The reactivity of CoPdesp2 was compared with its dirhodium counterparts in the aziridination of cyclic alkenes. Also, a biscarboxylate, HPH acid with the skeleton of xanthene was synthesized and tested on the dirhodium core in the aziridination reactions. Both of Rh2HPH2 and Rh2esp(OAc)2 were found to be competent catalysts in the intermolecular aziridination of cyclic alkenes. In‐between: Intermolecular aminations with catalysts with hetero/homo‐bimetallic cores were examined. Paddlewheel‐type complexes with a Co−Pd center, CoPd(OAc)4 and CoPd(esp)2 were found capable of catalyzing aziridinations of cycloalkenes and C−H bond amination. Additionally, a biscarboxylate, HPH acid was tested as the ligand on the dirhodium to compare the reactivities of the bimetallic catalysts. [ABSTRACT FROM AUTHOR]

A first example of Fe‐catalyzed dearomative amination of β‐naphthols with aryl azides is described. The method constructs a nitrogen‐containing quaternary carbon center catalyzed by cheap and readily available iron salt FeCl2, and affords a series of α‐amino‐β‐naphthalenones in good to excellent yields under simple and mild reaction conditions. Preliminary experimental and computational studies suggest that the reaction is probably initiated by iron‐iminyl diradical and followed by intramolecular hydrogen transfer to generate iron‐aminyl radical and finally an intramolecular radical combination reaction. [ABSTRACT FROM AUTHOR]

Abstract: Heteroscorpionate ligands of the bis(pyrazolyl)methane family have been applied in the stabilisation of terminal copper tosyl nitrenes. These species are highly active intermediates in the copper‐catalysed direct C−H amination and nitrene transfer. Novel perfluoroalkyl‐pyrazolyl‐ and pyridinyl‐containing ligands were synthesized to coordinate to a reactive copper nitrene centre. Four distinct copper tosyl nitrenes were prepared at low temperatures by the reaction with SO2tBuPhINTs and copper(I) acetonitrile complexes. Their stoichiometric reactivity has been elucidated regarding the imination of phosphines and the aziridination of styrenes. The formation and thermal decay of the copper nitrenes were investigated by UV/Vis spectroscopy of the highly coloured species. Additionally, the compounds were studied by cryo‐UHR‐ESI mass spectrometry and DFT calculations. In addition, a mild catalytic procedure has been developed where the copper nitrene precursors enable the C−H amination of cyclohexane and toluene and the aziridination of styrenes. [ABSTRACT FROM AUTHOR]

The synthesis, characterisation and application of anionic [CoII(Cor)]- (Cor = corrole) metalloradicals in the ringclosing C-H amination of an aliphatic azide in the presence of Boc2O (Boc = tert-butyloxycarbonyl) to give the corresponding Boc-protected N-heterocyclic product tert-butyl 2-phenylpyrrolidine-1-carboxylate are reported. This is the first example of the use of metalloradical cobalt(II) corrole complexes in nitrenetransfer reactions. On the basis of DFT calculations, the reaction is proposed to proceed via discrete open-shell nitrene radical intermediates bearing most of their spin density at the nitrene nitrogen atom. The [CoII(Cor)]- complexes are substantially faster catalysts than the corresponding neutral [CoII(porphyrin)] complexes when applied in the same ring-closing C-H amination reaction under identical reaction conditions. Increasing the electron density at cobalt(II) therefore has a positive influence on the reaction rate. [ABSTRACT FROM AUTHOR]

The development of catalysts capable of fast, robust C−H bond amination under mild conditions is an unrealized goal despite substantial progress in the field of C−H activation in recent years. A Mn-based metal-organic framework (CPF-5) is described that promotes the direct amination of C−H bonds with exceptional activity. CPF-5 is capable of functionalizing C−H bonds in an intermolecular fashion with unrivaled catalytic stability producing >105 turnovers. [ABSTRACT FROM AUTHOR]

Reduction of previously reported (ArL)FeCl with potassium graphite furnished a low-spin (S = 1/2) iron complex (ArL)Fe which features an intramolecular η6-arene interaction and can be utilized as an FeI synthon (ArL = 5- mesityl-1,9-(2,4,6-Ph3C6H2)dipyrrin). Treatment of (ArL)Fe with adamantyl azide or mesityl azide led to the formation of the high-spin (S = 5/2), three-coordinate imidos (ArL)Fe- (NAd) and (ArL)Fe(NMes), respectively, as determined by EPR, zero-field 57Fe Mössbauer, magnetometry, and single crystal X-ray diffraction. The high-spin iron imidos are reactive with a variety of substrates: (ArL)Fe(NAd) reacts with azide yielding a ferrous tetrazido (ArL)Fe(κ2-N4Ad2), undergoes intermolecular nitrene transfer to phosphine, abstracts H atoms from weak C-H bonds (1,4-cyclohexadiene, 2,4,6-tBu3C6H2OH) to afford ferrous amido product (ArL)Fe(NHAd), and can mediate intermolecular C-H amination of toluene [PhCH3/PhCD3 kH/kD: 15.5(3); PhCH2D kH/kD: 11(1)]. The C-H bond functionalization reactivity is rationalized from a two-step mechanism wherein each step occurs via maximal energy and orbital overlap between the imido fragment and the C-H bond containing substrate. [ABSTRACT FROM AUTHOR]

The development of iron catalysts for carbon-heteroatom bond formation, which has attracted strong interest in the context of green chemistry and nitrene transfer, has emerged as the most promising way to versatile amine synthetic processes. A diiron system was previously developed that proved efficient in catalytic sulfimidations and aziridinations thanks to an FeIIIFeIV active species. To deal with more demanding benzylic and aliphatic substrates, the catalyst was found to activate itself to a FeIIIFeIVL. active species able to catalyze aliphatic amination. Extensive DFT calculations show that this activation event drastically enhances the electron affinity of the active species to match the substrates requirements. Overall this process consists in a redox self-adaptation of the catalyst to the substrate needs. [ABSTRACT FROM AUTHOR]

Cobalt-catalyzed reactions of triazoles and dioxazol-5-one involving nitrene transfer were described. A number of amidated 1,2,3-trizole derivatives have been obtained in moderate to excellent yields. [ABSTRACT FROM AUTHOR]

Palladium(II) catalysis was found to be effective for intramolecular C-H amination in water. With 2-azidobiphenyls as substrates, the reaction efficiently provided various carbazoles with N2 as the sole byproduct. The reaction showed high functional-group tolerance and could be used in the synthesis of several natural carbazole alkaloids. The catalytic process was promoted by water, and the reaction was inefficient in the organic solvents that were investigated. [ABSTRACT FROM AUTHOR]

High-valent terminal copper-nitrene species have been postulated as key intermediates in copper-catalyzed aziridination and amination reactions. The high reactivity of these intermediates has prevented their characterization for decades, thereby making the mechanisms ambiguous. Very recently, the Lewis acid adduct of a copper-nitrene intermediate was trapped at −90 °C and shown to be active in various oxidation reactions. Herein, we describe for the first time the synthesis and spectroscopic characterization of a terminal copper(II)-nitrene radical species that is stable at room temperature in the absence of any Lewis acid. The azide derivative of a triazamacrocyclic ligand that had previously been utilized in the stabilization of aryl-CuIII intermediates was employed as an ancillary ligand in the study. The terminal copper(II)-nitrene radical species is able to transfer a nitrene moiety to phosphines and abstract a hydrogen atom from weak C−H bonds, leading to the formation of oxidized products in modest yields. [ABSTRACT FROM AUTHOR]

The RhII-catalyzed oxyamination and diamination of alkenes generate 1,2-amino alcohols and 1,2-diamines, respectively, in good to excellent yields and with complete regiocontrol. In the case of diamination, the intramolecular reaction provides an efficient method for the preparation of pyrrolidines, and the intermolecular reaction produces vicinal amines with orthogonal protecting groups. These alkene difunctionalizations proceed by aziridination followed by nucleophilic ring opening induced by an Rh-bound nitrene generated in situ, details of which were uncovered by both experimental and theoretical studies. In particular, DFT calculations show that the nitrogen atom of the putative [Rh]2=NR metallanitrene intermediate is electrophilic and support an aziridine activation pathway by N ⋅⋅⋅N=[Rh]2 bond formation, in addition to the N ⋅⋅⋅[Rh]2=NR coordination mode. [ABSTRACT FROM AUTHOR]

The intramolecular benzylic C−H amination catalyzed by bimetallic paddlewheel complexes was investigated by using density functional theory calculations. The metal-metal bonding characters were investigated and the structures featuring either a small HOMO-LUMO gap or a compact SOMO energy scope were estimated to facilitate an easier one-electron oxidation of the bimetallic center. The hydrogen-abstraction step was found to occur through three manners, that is, hydride transfer, hydrogen migration, and proton transfer. The imido N species are more preferred in the Ru-Ru and Pd-Mn cases whereas coexisting N species, namely, singlet/triplet nitrene and imido, were observed in the Rh-Rh and Pd-Co cases. On the other hand, the triplet nitrene N species were found to be predominant in the Pd-Ni and Pd-Zn systems. A concerted asynchronous mechanism was found to be modestly favorable in the Rh-Rh-catalyzed reactions whereas the Pd-Co-catalyzed reactions demonstrated a slight preference for a stepwise pathway. Favored stepwise pathways were seen in each Ru-Ru- and Pd-Mn-catalyzed reactions and in the triplet nitrene involved Pd-Ni and Pd-Zn reactions. The calculations suggest the feasibility of the Pd-Mn, Pd-Co, and Pd-Ni paddlewheel complexes as being economical alternatives for the expensive dirhodium/diruthenium complexes in C−H amination catalysis. [ABSTRACT FROM AUTHOR]

Dirhodium-catalyzed C-H amination is hypothesized to proceed via Rh2-nitrene intermediates in either the Rh2(II,Il) or Rh2(II,III) redox state. Herein, we report joint theoretical and experimental studies of the ground electronic state (GES), redox potentials, and C-H amination of [Rh2II,III(O2CCH3)4(L)n]+ (l_L) (L = none, Cl-, and H2O), [Rh2(esp)2]+ (2), and Rh2(espn)2Cl (3) (esp = α,α,α',α'-tetramethyl-1,3-benzenedipropanoate and espn = α,α,α',α'-tetramethyl-1,3-benzenedipropanamidate). CASSCF calculations on 1_L yield a wave function with two closely weighted configurations, (δ*)2(π1*)2(π2*)1 and (δ*)2(π1*)1(π2*)2, consistent with reported EPR g values [Chem. Phys. Lett. 1986, 130, 20--23]. In contrast, EPR spectra of 2 show g values consistent with the DFT-computed (π*)4δ*)1 GES. EPR spectra and Cl K-edge XAS for 3 are consistent with a (π*)4(<δ*)1 GES, as supported by DFT. Nitrene intermediates 2N_L and 3N_L are also examined by DFT (the nitrene is an NSO3R species). DFT calculations suggest a doublet GES for 2N_L and a quartet GES for 3N_L. CASSCF calculations describe the GES of 2N as Rh2(II,II) with a coordinated nitrene radical cation, (π*)4(δ*)2(δnitrene,1)1(πnitrene,2)0. Conversely, the GES of 3N is Rh2(II,III) with a coordinated triplet nitrene, (π*)4(δ*)1(πnitrene,1)1(πnitrene,2)1. Quartet transition states (4TSs) are found to react via a stepwise radical mechanism, whereas 2TSs are found to react via a concerted mechanism that is lower in energy compared to 4TSs for both 2N_L and 3N_L. The experimental (determined by intramolecular competition) and 2TS-calculated kinetic isotopic effect (KIE) shows a KIE ~ 3 for both 2N and 3N, which is consistent with a concerted mechanism. [ABSTRACT FROM AUTHOR]

A CuI catalyst (1), supported by a framework of strongly basic guanidinato moieties, mediates nitrene-transfer from PhI≡NR sources to a wide variety of aliphatic hydrocarbons (C-H amination or amidination in the presence of nitriles) and olefins (aziridination). Product profiles are consistent with a stepwise rather than concerted C-N bond formation. Mechanistic investigations with the aid of Hammett plots, kinetic isotope effects, labeled stereochemical probes, and radical traps and clocks allow us to conclude that carboradical intermediates play a major role and are generated by hydrogen-atom abstraction from substrate C-H bonds or initial nitrene-addition to one of the olefinic carbons. Subsequent processes include solvent-caged radical recombination to afford the major amination and aziridination products but also one-electron oxidation of diffusively free carboradicals to generate amidination products due to carbocation participation. Analyses of metal- and ligand-centered events by variable temperature electrospray mass spectrometry, cyclic voltammetry, and electron paramagnetic resonance spectroscopy, coupled with computational studies, indicate that an active, but still elusive, copper-nitrene (S = 1) intermediate initially abstracts a hydrogen atom from, or adds nitrene to, C-H and C≡C bonds, respectively, followed by a spin flip and radical rebound to afford intra- and intermolecular C-N containing products. [ABSTRACT FROM AUTHOR]

Copper complexes with chiral iminopyridine ligands were screened for their catalytic efficiency in carbene () and nitrene transfer reactions (, CH ). Both pre-formed and in situ formed complexes were considered. The results highlighted the poor catalytic efficiency of these complexes in employing methyl phenyldiazoacetate as the carbene source, whereas better results were obtained in nitrene transfer reactions, particularly in the of CH bonds, albeit the of the reactions was negligible in nearly all cases. Finally, copper complexes were also found to promote an interesting oxidative of alkynes with PhI(OAc)2 at room temperature. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

By using [Ru(TTP)CO] [H2TTP = meso-tetrakis(4-tolyl)porphyrin] as catalyst and aryl azides as the nitrene source, the sp2(C-H) bonds of a series of indoles undergo oxidative C -N bond formation to give unique 2,3-diimination products in good to high yields. [ABSTRACT FROM AUTHOR]

Nitrogen functional groups are found in many biologically active compounds and their stereochemistry has a profound effect on biological activity. Nitrene transfer reactions such as aziridination, C- H bond amination, and sulfimidation are useful methods for introducing nitrogen functional groups, and the enantiocontrol of the reactions has been extensively investigated. Although high enantioselectivity has been achieved, most of the reactions use ( N-arylsulfonylimino)phenyliodinane, which co-produces iodobenzene, as a nitrene precursor and have a low atom economy. Azide compounds, which give nitrene species by releasing nitrogen, are ideal precursors but rather stable. Their decomposition needs UV irradiation, heating in the presence of a metal complex, or Lewis acid treatment. The examples of previous azide decomposition prompted us to examine Lewis acid and low-valent transition-metal complexes as catalysts for azide decomposition. Thus, we designed new ruthenium complexes that are composed of a low-valent Ru( II) ion, apical CO ligand, and an asymmetry-inducing salen ligand. With these ruthenium complexes and azides, we have achieved highly enantioselective nitrene transfer reactions under mild conditions. Recently, iridium-salen complexes were added to our toolbox. [ABSTRACT FROM AUTHOR]

Highly functionalized tetrasubstituted alkenes were obtained by an unexpected amination reaction promoted by ethyl nosyloxycarbamate on various α-nitro aryl and heteroaryl enoates. A nitrene is likely the aminating species responsible for the observed insertion reaction leading to (E)-β-amino a-nitro enoates as the major products, regardless of the substrate configuration. The compounds, bearing two nitrogenous functional groups in different oxidation states, can be regarded as interesting synthons. In contrast, aziridination was observed for a-nitro alkyl enoates or β-nitro allylic alcohols. [ABSTRACT FROM AUTHOR]

An efficient asymmetric C-H amination of benzylic and allylic substrates, as well as of adamantane derivatives, through catalytic C-H insertion of a chiral nitrene is reported. The reaction involves a chiral rhodium(II) complex, an iodine(III) oxidant, and a sulfonimidamide as a nitrene precursor. Experimental protocols for the preparation of the reagents and the catalytic nitrene are provided. The C-H amination can provide the corresponding amino derivatives on a gram scale. Various methods for the cleavage of the sulfonimidoyl group to give the corresponding tert-butoxycarbonyl- or acetyl-protected optically pure amines are also described. [ABSTRACT FROM AUTHOR]

We examine important reactivity pathways relevant to stoichiometric and catalytic C-H amination via isolable β-diketiminato dicopper alkylnitrene intermediates {[Cl2NN]Cu}2(μ-NR). Kinetic studies involving the stoichiometric amination of ethylbenzene by {[Cl2NN]Cu}2(μ-NtBu) (3) demonstrate that the terminal nitrene [Cl2NN]Cu NtBu is the active intermediate in C-H amination. Initial rates exhibit saturation behavior at high ethylbenzene loadings and an inverse dependence on the copper species [Cl2NN]Cu, both consistent with dissociation of a [Cl2NN]Cu fragment from 3 prior to C-H amination. C-H amination experiments employing 1,4-dimethylcyclohexane and benzylic radical clock substrate support a stepwise H-atom abstraction/radical rebound pathway. Dicopper nitrenes [Cu]2(μ-NCHRR') derived from 1° and 2° alkylazides are unstable toward tautomerization to copper(I) imine complexes [Cu](HN CRR'), rendering 1° and 2° alkylnitrene complexes unsuitable for C-H amination. [ABSTRACT FROM AUTHOR]

The 7-coordinate complex [Fe(qpy)(MeCN)2](ClO4)2 (1, qpy = 2,2':6',2'':6'',2''':6''',2''''-quinquepyridine) is a highly active nonheme iron catalyst for intra- and intermolecular amination of C(sp3)-H bonds. This complex effectively catalyzes the amination of limiting amounts of not only benzylic and allylic C(sp3)-H bonds of hydrocarbons but also the C(sp3)-H bonds of cyclic alkanes and cycloalkane/linear alkane moieties in sulfamate esters, such as those derived from menthane and steroids cholane and androstane, using PhI-NR or "PhI(OAc)2 + H2NR" [R = Ts (p-toluenesulfonyl), Ns (p-nitrobenzenesulfonyl)] as nitrogen source, with the amination products isolated in up to 93% yield. Iron imide/nitrene intermediates [Fe(qpy)(NR)(X)]n+ (CX, X = NR, solvent, or anion) are proposed in these amination reactions on the basis of experimental studies including ESI-MS analysis, crossover experiments, Hammett plots, and correlation with C-H bond dissociation energies and with support by DFT calculations. Species consistent with the formulations of [Fe(qpy)(NTs)2]2+ (CNTs) and [Fe(qpy)(NTs)]2+ (C) were detected by high-resolution ESI-MS analysis of the reaction mixture of 1 with PhI=NTs (4 equiv). DFT calculations revealed that the reaction barriers for H-atom abstraction of cyclohexane by the ground state of 7-coordinate CNTs and ground state of C are 15.3 and 14.2 kcal/mol, respectively, in line with the observed high activity of 1 in catalyzing the C-H amination of alkanes under mild conditions. [ABSTRACT FROM AUTHOR]

Among the transition metals, copper-basedcatalyst systemsenablethe widest range of N-containing reagents in C–H aminationto allow for the direct incorporation of versatile N-based functionalities via ubiquitous C–H bonds. In additionto nitrene-based approaches involving sulfonyliminoiodinanes (PhINSO2R), diverse non-nitrene protocols have been developed thatallow for the direct use of organic amides, nitrosoarenes, and hydroxylamines,strained heterocycles such as oxaziridines, acetonitrile, secondarysulfonylamines, and even alkylamines and arylamines. Synthetic, mechanistic,and theoretical studies reveal discrete copper nitrenes [Cu]NRand copper amides [Cu]–NHR to be key reactive intermediatesin C–H amination. Copper-catalyzed sp3C–Hamination is reviewed, connecting catalytic reactivity patterns withlikely copper intermediates wherever possible, with the goal to stimulatethe further development of C–H functionalization reactionswith copper which possess significant sustainability advantages overother contemporary approaches involving noble metals. [ABSTRACT FROM AUTHOR]

C-H amination by iron-imido/nitrene species has attracted increasing research interest in recent years because of its potential use in economical and environmentally benign syntheses of amino compounds. With the aim of providing a comprehensive overview of this field, which is of interest to both the synthetic organic and inorganic communities, this paper reviews the status quo of C-H amination chemistry by iron-imido/nitrene intermediates, as well as by well-defined iron-imido/nitrene compounds, with special emphasis on their structure/reactivity correlations. Achievements, problems, and perspectives in this growing field are discussed. [ABSTRACT FROM AUTHOR]

High-valent copper-nitrene intermediates have long been proposed to play a role in copper-catalyzed aziridination and amination reactions. However, such intermediates have eluded detection for decades, preventing the unambiguous assignments of mechanisms. Moreover, the electronic structure of the proposed copper-nitrene intermediates has also been controversially discussed in the literature. These mechanistic questions and controversy have provided tremendous motivation to probe the accessibility and reactivity of CuIII-NR/CuIIN•R species. In this paper, we report a breakthrough in this field that was achieved by trapping a transient copper-tosylnitrene species, 3-Sc, in the presence of scandium triflate. The sufficient stability of 3-Sc at −90 °C enabled its characterization with optical, resonance Raman, NMR, and X-ray absorption near-edge spectroscopies, which helped to establish its electronic structure as CuIIN•Ts (Ts = tosyl group) and not CuIIINTs. 3-Sc can initiate tosylamination of cyclohexane, thereby suggesting CuIIN•Ts cores as viable reactants in oxidation catalysis. [ABSTRACT FROM AUTHOR]

A number of azidoboranes having substitution patternsthat arederived from catechol (3), pinacol (4a),1,2-diaminoethane (4b,c), 1,2-ethanedithiol(4d), and 1,2,4,5-tetrahydroxybenzene as well as acyclicdialkoxy species (5) were synthesized and,in the case of 4c(N,N′-ditosyl-2-azido-1,3,2-diazaborolane), also structurallycharacterized. The azidoboranes were photolyzed in cyclohexane solventin order to investigate the tendency of the generated borylnitrenesto undergo intermolecular C–H insertion reactions. The yieldsof intermolecular insertion products ranged from very good (4a) to vanishingly small, depending on the substitution ofthe azidoborane. For a number of borylnitrenes the zero-field splittingparameter Dwas measured in organic glasses at 4K. The small primary kinetic isotope effect (kH/kD= 1.35) measured for 4ain mixtures of [H12]cyclohexane and [D12]cyclohexane suggests that the insertion reaction is concerted andinvolves the singlet state of the borylnitrene. Computations at theCBS-QB3 and CCSD(T)/TZ2P levels of theory show that the relative energiesof singlet and triplet states of a wide variety of borylnitrenes andeven their nature as minima or saddle points depend strongly on thesubstituents. Photolysis of the most reactive azidoborane, 4a, in methane in a flow reactor at atmospheric pressure produces anintermolecular insertion product in low yields, in agreement withthe expectation of intersystem crossing to the less reactive tripletstate of the borylnitrene. [ABSTRACT FROM AUTHOR]

Rhodium(II) dicarboxylate complexes were discovered to catalyze the intramolecular amination of unactivated primary, secondary, or tertiary aliphatic C-H bonds using aryl azides as the N-atom precursor. While a strong electron-withdrawing group on the nitrogen atom is typically required to achieve this reaction, we found that both electron-rich and electron-poor aryl azides are efficient sources for the metal nitrene reactive intermediate. [ABSTRACT FROM AUTHOR]

The l-epi-capreomycidine (Cpm) derivatives were efficiently and stereoselectively synthesized via nitrene C–H insertion starting from a readily available d-Tyr. Design of a substrate that takes into account hydrogen bonding is a critical feature in order to achieve high selectivity. Our synthetic strategy could be a new access to epi-Cpm and its derivatives, which are found in several biologically active natural products. [ABSTRACT FROM AUTHOR]

Metalloporphyrins are a class of versatile catalysts with the capability to functionalize saturated C–H bonds viaseveral well-defined atom/group transfer processes, including oxene, nitrene, and carbene C–H insertions. The corresponding hydroxylation, amination, and alkylation reactions provide direct approaches for the catalytic conversion of abundant hydrocarbons into value-added functional molecules through C–O, C–N, and C–C bond formations, respectively. This tutorial reviewdescribes metalloporphyrin-based catalytic systems for the functionalization of different types of sp3C–H bonds, both inter- and intramolecularly, including challenging primary C–H bonds. Additional features of metalloporphyrin-catalyzed C–H functionalization include unusual selectivities and high turnover numbers. [ABSTRACT FROM AUTHOR]

The first amide-directed, palladium-catalyzed, intermolecular, highly selective C-H aminations with the non-nitrene-based nitrogen source N-fluorobenzenesulfonimide have been developed. This methodology might provide a new pathway for directed metal-catalyzed aromatic C-H amination. [ABSTRACT FROM AUTHOR]

Stereoselective catalytic intermolecular C–H amination of complex molecules is reported. Site-selective functionalizations occur with very good yields up to 91% and excellent d.e.s up to 99%. However, the precise nature of the nitrene C–H insertion remains a matter of debate despite several physical organic experiments. [ABSTRACT FROM AUTHOR]

Abstract: α-Aryl-α-aminocarbonyloxime O-pentafluorobenzoates are found to be promising precursors for synthesis of 2,3-disubstituted indole derivatives catalyzed by PdCl2(MeCN)2 in the presence of MgO as a base. The reaction is supposed to proceed via intramolecular aromatic C–H amination of a vinyl nitrene–palladium intermediate. [ABSTRACT FROM AUTHOR]

2,2,2-Trichloroethoxycarbonyl azide (TrocN3) is an effective nitrene source for cobalt(II)-catalyzed intermolecular nitrene insertion of C−H bonds. Among different metalloporphyrins studied, Co(II)(TPP) was shown to be a competent catalyst for the selective amination of various benzylic C−H bonds under mild conditions without the need of other reagents or additives, forming the desired Troc-protected amines in moderate to high yields with nitrogen gas as the only byproduct. [ABSTRACT FROM AUTHOR]

This review article summarizes C-H functionalization-based synthesis of indoles and related structures (e.g. carbazoles and indolines) with an emphasis on literature after 2000. The discussion is organized into four broadly defined sections: a) via nitrene or carbene insertion into a C-H bond; b) via direct coupling of two sp2 carbon centers; c) via transition-metal catalyzed C-H amination and d) other strategies. [ABSTRACT FROM AUTHOR]

Recent developments in catalytic C–H amination are discussed in this feature article. The careful design of reagents and catalysts now provides efficient conditions for exquisitely selective intramolecular as well as intermolecular nitrene C–H insertion. The parallel emergence of C–H activation/amination reactions opens new opportunities complementary to those offered by nitrenes. [ABSTRACT FROM AUTHOR]

Nitrene transfer reactions represent a useful methodology to synthesize in a few steps high added-value compounds used as organic intermediates. Herein, we describe the catalytic activity of metal porphyrin complexes in a wide range of reactions such as C–H hydrocarbon amination and olefin aziridination to synthesize nitrogen containing molecules. All the most important nitrene sources have been reviewed stressing the potentiality and limits of each one in the particular class of chemical transformation. [ABSTRACT FROM AUTHOR]