Dinitrogen Extrusion Research Articles

Density Functional Study on the Mechanism of Nickel-Mediated Diazo Carbonylation

The mechanism of diazo activation as well as the carbonylation of the resulting carbene complexes has been investigated by means of DFT calculations at the PBE0/TZVP level of theory. The free energy profile of all elementary steps of the reaction, i.e., diazo coordination, dinitrogen extrusion, carbene–CO coupling, CO coordination, and ketene elimination, have been elucidated for diazomethane and ethyl diazoacetate as substrates and for Ni(CO)3, Ni(CO)2(PH3), and Ni(dtbpe)(CO) (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) as precursors. The reaction rate is determined by the formation of the coordinatively unsaturated precursor followed by the dinitrogen extrusion, regardless of the initial diazo compound and the catalyst precursor. For the homoleptic precursor Ni(CO)3 the free energy of activation for diazomethane and ethyl diazoacetate (EDA) is 16.9 and 22.4 kcal/mol, respectively. The replacement of one carbonyl ligand with PH3 results in a decrease in the activation barrier, modifying the energies to 15.7 and 20.5 kcal/mol, respectively. The activation free energy of the diazo extrusion step promoted by Ni(dtbpe)(CO) is 24.3 kcal/mol for diazomethane and 28.1 kcal/mol for EDA. The formation of carbene complexes is slightly endergonic starting from the homoleptic precursor and exergonic for the phosphine-substituted complex. The carbene–CO coupling, resulting in coordinatively unsaturated ketene complexes, is a fast and highly exergonic process with reaction free energies between −32.3 and −42.1 kcal/mol, depending on the substituents. Under a carbon monoxide atmosphere the ketene complexes may uptake one CO, forming coordinatively saturated ketene complexes via low barriers in exergonic reactions. The final step, i.e., the dissociation of ketene or ethoxycarbonylketene from the saturated ketene complex, regenerates the corresponding nickel–carbonyl precursor. The azine formation side reaction for the simplest case between Ni(CO)3 and diazomethane has been also examined and found to be highly exergonic; however, the large free energy barrier prevents the formation of benzophenone-azine when CO is also present.

ChemInform Abstract: Multifunctionalized 3‐Hydroxypyrroles in a Three‐Step, One‐Pot Cascade Process from Methyl 3‐TBSO‐2‐diazo‐3‐butenoate and Nitrones.

AbstractThe copper‐catalyzed Mannich addition is followed by rhodium‐catalyzed dinitrogen extrusion.

ChemInform Abstract: Unprecedented Intramolecular [3 + 2] Cycloadditions of Azido‐Ketenimines and Azido‐Carbodiimides. Synthesis of Indolo[1,2‐a]quinazolines and Tetrazolo[5,1‐b]quinazolines.

AbstractA series of azido‐ketenimines (V) and azido‐carbodiimines (XII) is prepared.

Multifunctionalized 3-Hydroxypyrroles in a Three-Step, One-Pot Cascade Process from Methyl 3-TBSO-2-diazo-3-butenoate and Nitrones

The synthesis of N-aryl-2-carboxyl-3-hydroxy-5-arylpyrroles has been achieved in high yield by the combination of a TBSO-substituted vinyldiazoacetate and nitrones in a one-pot cascade process involving copper-catalyzed Mannich addition, dirhodium-catalyzed dinitrogen extrusion and N-OTBS insertion, and acid-promoted aromatization (elimination).

Divergent outcomes of carbene transfer reactions from dirhodium- and copper-based catalysts separately or in combination.

Divergent outcomes of carbene transfer reactions from dirhodium- and copper-based catalysts separately or in combination.

Unprecedented intramolecular [3 + 2] cycloadditions of azido-ketenimines and azido-carbodiimides. Synthesis of indolo[1,2-a]quinazolines and tetrazolo[5,1-b]quinazolines

N-(2-azidomethyl)phenyl ketenimines and N-(2-azidomethyl)phenyl-N'-alkyl(aryl) carbodiimides undergo, under mild thermal conditions, intramolecular [3 + 2] cycloaddition reactions between the azido group and either the C=C or the distal C=N double bonds of the ketenimine and carbodiimide functions respectively. The reaction products are indolo[1,2-a]quinazolines and/or indolo[2,1-b]quinazolines in the case of azido-ketenimines, and tetrazolo[5,1-b]quinazolines in the case of azido-carbodiimides. The formation of the two classes of indoloquinazolines implies the ulterior dinitrogen extrusion from the non-isolated, putative [3 + 2] cycloadducts between the azide and ketenimine functions, whereas in the case of azido-carbodiimides the initial cycloadducts, tetrazoloquinazolines, were cleanly isolated and further converted into 2-aminoquinazolines by thermally induced dinitrogen extrusion.

Pericyclic Reaction of a Zwitterionic Salt of an Enedione-diazoester. A Novel Strategy for the Synthesis of Highly Functionalized Resorcinols

Enedione-diazoesters formed from 3-TBSO-2-diazo-3-butenoates undergo base-catalyzed pericyclization that with dinitrogen extrusion and methyl migration provide a novel and efficient route to 2-carboalkoxyresorcinols. Intercepting the intermediate enolate anion with methyl vinyl ketone leads to the corresponding 4-substituted 2-carboalkoxyresorcinol and suggests generalization of this methodology.

Nickel-Catalyzed Denitrogenative Annulation Reactions of 1,2,3-Benzotriazin-4(3H)-ones with 1,3-Dienes and Alkenes

1,2,3-Benzotriazin-4(3H)-ones react with 1,3-dienes in the presence of a nickel(0)/phosphine complex to give a variety of 3,4-dihydroisoquinolin-1(2H)-ones. Oxidative insertion of nickel(0) into the triazinone moiety prompts extrusion of dinitrogen to give a five-membered ring azanickelacyclic intermediate. Subsequent insertion of 1,3-dienes into the nickel-carbon bond followed by allylic amidation affords 3,4-dihydroisoquinolin-1(2H)-ones. Alkenes also undergo insertion into the five-membered ring azanickelacyclic intermediate, and subsequent reductive elimination gives 3-substituted 3,4-dihydroisoquinolin-1(2H)-ones.

Dinitrogen extrusion from diazidophenylborane: Computational analysis of PhBN x ( x = 6, 4, 2) isomers

The energies and structures of possible intermediates in the dinitrogen extrusion from diazidophenylborane 4a to give phenylborylene 11a were determined using density functional (B3LYP), multiconfigurational (CASSCF and MRMP2), and coupled cluster (CCSD(T)) computations in conjunction with basis sets of up to cc-pVTZ quality. Formation of 11a and nitrogen from 4a is an exothermic process (−21 kcal mol −1). The triplet electronic ground state of azidophenylborylnitrene 5a (PhBN 4) is only 26 kcal mol −1 higher in energy than 4a and the phenyl shift in 5a to yield N-azidophenyliminoborane 7a is highly exothermic.

Preparation, Characterization, and Properties of 7-Nitrotetrazolo[1,5-f ]furazano[4,5-b]pyridine 1-Oxide

ABSTRACT The synthesis, characterization, and properties of 7-nitro-tetrazolo[1,5-f]furazano[4,5-b]pyridine 1-oxide (NFP) are reported. NFP is prepared by the diazotization of 3,6-di(hydrazino)-3,5-di(nitro)pyridine followed by the extrusion of molecular dinitrogen and ring closure.

Oxorhenium Complexes as Aldehyde‐Olefination Catalysts

Several oxorhenium compounds in the formal oxidation states V and VII are examined as catalysts for the aldehyde-olefination starting from diazo compounds, phosphines, and aldehydes. Of these, [ReMeO2(eta2-alkyne)] complexes provide the simplest catalysts to study, although [ReOCl3(PPh3)2] still remains the most efficient rhenium catalyst for aldehyde-olefination described to date. Prior to the reaction with the Re catalysts the phosphine and the diazo compound react to form a phosphazine. No catalytic reaction occurs in cases where no phosphazine formation is observed. The first step of the catalytic cycle involves the formation of a carbene intermediate by the reaction of phosphazine and catalyst under extrusion of phosphine oxide and dinitrogen. In a second step the carbene reacts with aldehyde under olefin formation and catalyst regeneration. Excess of alkyne as well as the presence of ketones slows down the catalytic reaction. The olefination of 4-nitrobenzaldehyde with diazomalonate is possible with these Re catalysts. In contrast, this reaction does not take place either in the classical Wittig fashion from Ph3P=C(CO2Et)2 and aldehyde or by use of all other catalysts for aldehyde olefination reactions reported to date. Catalytic ylide formation from diazo compounds seems therefore not to be the only pathway through which catalytic aldehyde-olefination reactions can proceed.

An S(N)2-like transition state for alkene episulfidation by dinitrogen sulfide.

Episulfidation of alkenes by dinitrogen sulfide, generated from thermolysis of 5-aryloxy-1,2,3,4-thiatriazoles, was found to be an S(N)2-like reaction involving simultaneous sulfur addition and dinitrogen extrusion. The preference for the one-step S(N)2 mechanism instead of the two-step (2+3) dipolar cycloaddition and denitrogenation is attributed to the higher geometry distortion penalty in the (2+3) transition state than that in the S(N)2-like transition state.

Mechanistic studies of direct and sensitized photolysis of methyl (4-nitrophenyl)diazoacetate in the presence of an electron-donating amine: photochemical generation of the diazoalkane radical anion

The direct and perylene-sensitized photolysis of methyl (4-nitrophenyl)diazoacetate (1) in the presence of an electron-donating amine was investigated by the characterization of reaction products and by the direct observation of reactive species using a laser flash photolysis technique. In the direct photolysis of 1 in the presence of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), electron transfer from TMPD occurs and the photoproducts are obtained through an intermediate other than the carbene 3, which we suppose to be the carbene radical anion 3−˙. In the perylene-sensitized photolysis of 1 in the presence of an amine having a large electron-donating ability such as N,N-dimethylaniline and TMPD, the radical anion of 1 can be generated by perylene-mediated electron transfer from the amine to 1. The resulting 1−˙ appears to undergo extrusion of dinitrogen to give 3−˙ smoothly, the behavior of which is dependent on the amine employed as an additive. The product studies revealed that 3−˙ reacts readily with O2 to give the ketoester 5 or abstracts hydrogen atoms to give the ester 7, which is not inconsistent with the theoretical prediction that 3−˙ has a σ radical character in its electronic structure.

Exploiting the Confined Reactivity ofC2v-Symmetrical Pentakis-Adducts of [60]Fullerene: Regioselective Formation of Hexakis-, Heptakis-, and Octakis-Adducts with Novel Addition Patterns by Addition of Diazomethane Followed by Dinitrogen Extrusion

A series of hexakis- to octakis-adducts of C60 with novel addition patterns was synthesized by 1,3-dipolar cycloaddition of diazomethane (CH2N2) to pentakis-adducts, whose reactivity is confined to a single 6-6 bond (bond at the intersect between two hexagons), followed by thermal N2 extrusion and rearrangement. Starting from pentakis-adducts 1a,b or 13, hexakis-adducts (±)-3a,b and (±)-17 with one 6-5 open methano bridge (bridge at the junction between a hexagon and a pentagon) were obtained in high yield (Schemes 1 and 6). Further conversion with CH2N2 at −80 to −60° provided heptakis-adducts 6a,b and 18, respectively, with two 6-5 open methano bridges (Schemes 2 and 6). Upon reacting (±)-3a,b at 0° with a large excess of CH2N2, octakis-adducts, (±)-5a,b with three 6-5 open methano bridges were obtained (Scheme 2). Oxidation of the 6-6 double bond, from which the two vicinal methano bridges in heptakis-adducts 6a and 18 depart, did not give the desired diketones with an opened fullerene shell, but only led to the 1,2-diols 14 and 19, respectively (Schemes 5 and 6). The nature of the addends in the various addition patterns did not affect the regioselectivity of the 1,3-dipolar cycloaddition of CH2N2 and the subsequent N2-extrusion process. The reactivity was, however, affected by the nature of the addends, and compounds bearing only fused cyclopropane rings were found to be better dipolarophiles than those bearing both fused cyclopropane and cyclohexene rings. Frontier-orbital theory provided reliable models for rationalizing both the occurrence and regioselectivity of the observed cycloaddition processes. The regioselectivity of the thermal and photochemical N2 extrusion from CH2N2 adducts of highly functionalized C60 derivatives is identical to that observed for CH2N2 adducts of the parent fullerenes C60 (C61H2N2) or C70 (C71H2N2). It is also similar to that previously reported by Klarner et al. for the thermal and photochemical N2 elimination from diazoalkane-toluene adducts. The experimental results, together with high-level ab initio and density-functional calculations, provide strong evidence that thermal N2 extrusion from all of these pyrazoline derivatives proceeds via a common mechanism, an eight-electron, orbital-symmetry-controlled [2πs+2πs+2σa+2σs] concerted process via an aromatic transition state (Schemes 7 and 8).

Theoretical Investigation of the Origin of Regioselectivity in the Formation of Methanofullerenes by Addition of Diazo Compounds: A Model Study

A Möbius aromatic transition state with a highly anisotropic magnetic susceptibility is involved in the thermal extrusion of dinitrogen from the adduct of benzene with diazomethane ([Eq. (1)]). A similar mechanism is proposed for the formation of 6–5-open methanofullerenes by thermal extrusion of dinitrogen from the pyrazolines that are obtained by 1,3-cycloaddition of diazoalkanes to fullerenes.

Reactions of C2ν-symmetrical C60 pentakis-adducts with diazomethane: regioselective formation of hexakis- to octakis-adducts and mechanism of methanofullerene formation by addition of diazomethane followed by dinitrogen extrusion

Repeated treatment of the C 2ν -symmetrical C 60 pentakis-adducts 1a,b with diazomethane provided with high regioselectively the novel heptakis- 5 and octakis-adducts 4a,b via hexakis-adducts 3a,b; an orbital symmetry-controlled reaction mechanism for the thermal dinitrogen extrusion from the pyrazoline intermediates in the addition of diazomethane to fullerenes is proposed.

Synthesis of the benzothiophen analogue of biphenylene by fvp

Extrusion of dinitrogen from the cinnoline (2) by flash vacuum pyrolysis (FVP) gave the benzothiophen analogue of biphenylene (3), which is more stable than the corresponding thiophen derivative.

Synthesis of hexahalogeno-1,8-diazabiphenylenes; separation of steric and electronic effects in extrusion of dinitrogen from benzo[c]cinnoline system, and the X-ray crystal structure of octachlorobenzo[c]cinnoline

Thermal extrusion of dinitrogen from hexafluoro- and hexachloro-4,5,9,10-tetra-azaphenanthrenes gives hexafluoro- and hexachloro-1,8-diazabiphenylenes under conditions which contrast with the relatively easy dediazatation of octachlorobenzo[c]cinnoline whose X-ray crystal structure shows severe distortion.

Ligand Abstraction in the Reaction of Aryldiazonium Ions with some Iron Complexes Containing Coordinated Cysteine, Maleonitriledithiol, or Triarylphosphine

The reactions of selected aryldiazonium tetrafluoroborates with Fe(CO)3(PR3)2, [Fe(mnt)2]−, [Fe(cystH)2]2+, and [Fe(CO)2(cyst)2] (mnt = S2C2(CN)2, cyst = SCH2CH(NH2)CO2H ) result in abstraction of the ligand to yield arenediazophosphonium ions, S-(arenediazo)cysteine or the dinitrogen extrusion product ArS(CN)C=C(CN)SAr. Arylazo complexes of iron were not obtained. The products have been characterized and compounds related to S-(arenediazo)cysteine, namely S-(arenediazo)triphenylmethyl mercaptan and S-(arenediazo)sulfones, have been synthesized for a detailed comparison of their Raman spectra. Assignments of ν(N=N) are made on the basis of 15N- and 2H-substitution experiments. The possible involvement of nucleophilic sulfur as a site for the activation and or reduction of complexed dinitrogen in biological nitrogen fixation is proposed.