Hydrazonium Ion Research Articles

DFT study on the organocatalytic carbonyl–olefin metathesis

Organocatalytic carbonyl–olefin metathesis has been given a systematic theoretical study with density functional theory (DFT) method. The catalytic cycle includes three key steps: (a) (3+2) cycloaddition of (E/Z)-hydrazonium ion I (from the reaction of aldehyde with the hydrazine catalyst) with olefin to produce pyrazolidinium ion II; (b) proton transfer between two nitrogen atoms in II to give pyrazolidinium ion III; (c) cycloreversion of III to produce hydrazonium ion IV, whose hydrolysis leads to the metathesis product. It is found that the stereo-selectivity of product is determined by the first step. The catalyst with high steric effect can effectively improve the stereo-selectivity. The second step, namely the proton transfer, is the rate-determining step in the whole catalytic cycle. Water molecule can effectively facilitate this step. In the third step, olefins with high strain, such as cyclopropene substrate, favor the cycloreversion.

A Catalytic Asymmetric 6 π Electrocyclization: Enantioselective Synthesis of 2‐Pyrazolines

A closer look at α,β-unsaturated hydrazonium ions reveals that they are isoelectronic to the pentadienyl anion, making them suitable substrates to undergo 6π electrocyclizations. The enantioselective catalysis of this transformation is achieved for the first time by asymmetric Brønsted acid catalysis.

Experimental evidence of formation of imines in the course of reduction of hydrazones

The reduction of hydrazones is generally suggested to proceed through a reductive cleavage of the nitrogen–nitrogen bond followed by a reduction of the carbon–nitrogen bond. This sequence of reduction processes is here supported for fluorenone (V) and benzophenone (VI) hydrazones as well as by a comparison of the reduction of fluorenone and benzophenone hydrazonium ions (I,III) with corresponding imines (II,IV). Another proof of the presence of imines as intermediates is the splitting of four-electron waves of hydrazones V and VI and hydrazonium ions I and VIII into two waves at pH < 2. This has been interpreted as due to differences in slopes d E 1/2/dpH and p K a-values of protonated hydrazine derivatives on one side and corresponding imines on the other. In this pH-range imines formed in reductions of VI and VIII are reduced in a single two-electron wave, those of I and V in two one-electron steps. Fluorenone imine (II) is sufficiently stable to allow recording of time-independent current–voltage curves between pH 6 and 11. In this pH-range the imine (II) is reduced in two one-electron steps. Benzophenone imine (IV) has been found stable between pH 4.6 and 12. At pH 4.6–8 the reduction of the imine IV takes place in a single two-electron step, at pH 8–12 in two one-electron steps. Final proof of the initial cleavage of the N–N bond is presented by comparison with the reduction of nitrones.

Synthesis of the necine bases (±)-macronecine and (±)-supinidine via an aza-ene reaction and allylsilane induced ring closure

An aza-ene reaction has been used for the first time for the synthesis of two 5-membered lactam-hydrazides, each with a built-in allylsilane terminator for further elaboration. One of the lactam-hydrazides was transformed via an allylsilane-hydrazonium ion ring closure to a fused tetrahydropyrazole which may be considered as a mono-nitrogen analog of the biologically significant necine bases. A density functional theoretical study (B3LYP/6-21G*) was undertaken to provide insight into the factors that favor a synclinal transition structure of the hydrazonium ion intermediate leading to the tetrahydropyrazole. This stereocontrolled synthesis served as a model for the multi-step conversion of the other lactam-hydrazide, the substituted 2-pyrrolidinone, to necine bases (±)-supinidine and (±)-macronecine. An allylsilane-aldehyde ring closure formed the key step in the synthesis of these natural products.

Nitrogen Trioxide in Irradiated Aqueous Nitric Acid Solutions of Hydrazine

The rate constants of reactions of the NO3•radical with hydrazoic acid (7.6 × 106l mol–1s–1) and the hydrazonium ion (2.3 × 106l mol–1s–1) in 6 M nitric acid at 290 ± 2 K were measured by a pulse radiolysis technique. The reaction scheme was refined by the computer simulation of the γ-radiolysis of aqueous nitric acid solutions of hydrazine with the use of the measured rate constants and published data on the reactivity of intermediates. The results of computations were compared with experimental data on the continuous radiolytic degradation of hydrazine in aqueous 2 M nitric acid solutions at 313 K.

Lewis acid-mediated S N2 type displacement by grignard reagents on chiral perhydropyrido[2,1- b]pyrrolo[1,2- d][1,3,4]oxadiazine. Chirality induction in asymmetric synthesis of 2-substituted piperidines

Et 2AlCl-mediated nucleophilic alkylation with Grignard reagents on chiral perhydropyrido[2,1- b]pyrrolo[1,2- d][1,3,4]oxadiazine has proved to proceed via an S N2 mechanism at low temperatures (below −80 °C) with high to excellent inversive stereoselection, while, at an elevated temperature, hydrazonium ions are formed preferentially leading to retentive stereoselection. This methodology provides useful access to enantioselective preparation of 2-substituted piperidines and is used for asymmetric synthesis of (+)-coniine.

ChemInform Abstract: Asymmetric Synthesis of 1‐Substituted Tetrahydroisoquinolines by Nucleophilic Addition to Hydrazonium Ions. Application to the Enantioselective Syntheses of (+)‐ and (‐)‐Salsolidines and (‐)‐ Cryptostyline II.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric Synthesis of 1-Substituted Tetrahydroisoquinolines by Nucleophilic Addition to Hydrazonium Ions. Application to the Enantioselective Syntheses of (+)- and (−)-Salsolidines and (−)-Cryptostyline II

Nucleophilic addition of carbon nucleophiles and metal hydride reagents to hydrazonium salts modified by optically active 2-substituted pyrrolidine auxiliaries leads to highly enantioselective synthesis of 1-substituted tetrahydroisoquinolines. This methodology was applied to asymmetric synthesis of the title isoquinoline alkaloids.

Asymmetric synthesis of 1-substituted tetrahydroisoquinolines by nucleophilic addition to hydrazonium ions. Application to the enantioselective syntheses of (+)- and (−)-salsolidines and (−)-cryptostyline II

Nucleophilic addition of carbon nucleophiles and metal hydride reagents to hydrazonium salts modified by optically active 2-substituted pyrrolidine auxiliaries leads to highly enantioselective synthesis of 1-substituted tetrahydroisoquinolines. This methodology was applied to asymmetric synthesis of the title isoquinoline alkaloids.

Asymmetric Synthesis of 1-Substituted Tetrahydroisoquinolines by Nucleophilic Addition to Hydrazonium Ions. Application to the Enantioselective Syntheses of (+)- and (−)-Salsolidines and (−)-Cryptostyline II

Asymmetric Synthesis of 1-Substituted Tetrahydroisoquinolines by Nucleophilic Addition to Hydrazonium Ions. Application to the Enantioselective Syntheses of (+)- and (−)-Salsolidines and (−)-Cryptostyline II

Mechanism of the Beckmann rearrangement of formaldehyde oxime and formaldehyde hydrazone in the gas phase

The potential energy surfaces corresponding to the Beckmann rearrangement of protonated formaldehyde oxime and formaldehyde hydrazone in the gas phase have been explored using ab initio molecular orbital calculations. Geometries of stationary points were optimized at the HF and MP2/6–31G(d,p) level while relative energies were estimated at the MP4SDTQ/6–311++ G(d,p) level and corrected for zero-point energies. Both rearrangements are calculated to be concerted with a single transition structure, connecting the protonated species and the product complex. In the transition structure, the 1,2-hydrogen shift from C to N is accompanied by a lengthening of the N–O (in oxime) or N–N (in hydrazone) distance, and the migrating hydrogen is in trans relative to the leaving group across the CN bond. The transition structure in the hydrazone case is much closer to the final products than that in the oxime. This is also manifested by the energy barriers that amount to 44 and 189 kJ mol–1 for oxime and hydrazone, respectively. These results suggest that the Beckmann rearrangement of oxonium ion is a facile process, while that of hydrazonium ion is reachable under thermal conditions. The experimentally observed loss of HCN from hydrazonium ion can be better rationalized in terms of a Beckmann rearrangement than a 1,2-cis-elimination as recently proposed. The proton affinities at different sites in oxime and hydrazone are also evaluated.

Aspects of the CH 5N 2 potential energy surface: ions CH 3NHNH +, CH 3NNH 2+ and CH 2NHNH 2+ and radicals CH 2NHNH [rad]2 studied by theory and experiment

The CH 5N + 2 system has been investigated by ab initio MO calculations at the SDCl/6-31G**//6-31G** level of theory and by mass spectrometric experiments. The calculations confirm earlier experimental observations that the diazapropylium ions CH 3NHNH +, 1 +, CH 3NNH + 2, 2 + and CH 2NHNH + 2, 3 + and the hydrazonium ion CH 2NNH + 3, 4 +, are stable species. Theory predicts 1 + and 2 + to be higher in energy than 3 +, by 7–8 kcal mol −1, causing a serious discrepancy with existing experimental values, which indicate that 1 + and 2 + are considerably more stable than 3 +. The theoretical values are insensitive to inclusion of electron correlation in the geometry determinations. From a critical evaluation of existing energetic data for N 2H + 3, CH 5N + 2 and C 2H 7N + ions, and collision experiments on deuterium labelled species, it is concluded that theory is correct and that several reported appearance energy (AE) measurements on hydrazines are probably in error owing to interferences from traces of amines. From AE measurements not affected by these interferences, Δ H f( 3 +) is proposed to be 204 ± 5 kcal mol −1 from which theory leads us to recommend Δ H f values of 211 ± 5 kcal mol for 1 + and 2 +. Ab initio calculated proton affinities for HNNH, CH 3NNH and CH 3-NNCH 3 lead to proposed enthalpies for 1 + and 2 + which are consistent with these values. Theory further predicts the ring-closed form of 3 + to be a remarkably stable species (16.7 kcal mol −1 above 3 +) but the hydrogen bridged entity CH 2 = N H 2H 2 + previously proposed to be responsible for the facile interconversion between 3 + and 4 +, is not a minimum on the potential energy surface. In fact, large energy barriers (42–63 kcal mol −1) prohibit interconversion among ions 1 +, 2 +, 3 + and 4 +, via 1,2-H shifts. Metastable CH 5 N + 2 ions dissociate to HCN + NH + 4 and to HCNH + + NH 3 and in agreement with experiment, the reacting configuration for HCN formation is the ion 4 +. Formation of HCN from 4 + is exothermic but the reverse barrier is large (84 kcal mol −1) thus accounting for the persistence of 4 + in the gas phase and in neutral solvents. The small kinetic energy release (KER) accompanying this reaction is rationalized in terms of ion/dipole attraction in the dissociating [HCN⋯NH 4] + complex.

An infrared and raman study of the phase transitions and the torsional barrier in hydrazonium sulfate, N 2H 6SO 4

Infrared and Raman spectra of N 2H 6SO 4 have been investigated through the phase transitions at 230 K (III-II) and 483 K (II-I) and assignments made to the various vibrational modes. The assignments have been confirmed by studies of the deuterated compound. The internal modes of both N 2H 6 2+ and SO 4 2− ions show marked changes across the phase transitions. The torsional mode of N 2H 6 2+ with a fundamental frequency of 517 cm −1 in the room-temperature phase II, disappears in the high-temperature phase, I, accompanied by the appearance of the v q bending mode at 845 cm −1. The torsional barrier is estimated to be ≈32 kJ mol −1. The hydrazonium ion in the high-temperature phase is comparable to ethane. The SO 4 2− ion bands also show marked changes across the phase transitions, the v 1 and v 2 bands disappearing in the high-temperature phase. In the low-temperature phase, III, both molecular ions are more distorted than in the room-temperature phase.

Preparation od Cyclic a-Hydrazino Acids through N-Acylhydrazonium Intermediates

An efficient synthesis of bicyclic hydrazine derivatives (5a) and (5b) through the intermediacy of exocyclic hydrazonium ions (4a) and (4b) is described

Reaction of aromatic aldehydes with 1,2-dibenzylhydrazine

The reactions of 1,2-dibenzylhydrazine with several aromatic aldehydes in refluxing toluene gave the benzaldehyde dibenzylhydrazones (9) and (13) in high yield. It is suggested from labelling studies and from the failure to trap an azomethine imine in the reaction between dibenzylhydrazine and benzaldehyde that such intermediates are not involved in the formation of the hydrazones. These products may be formed directly via hydride transfer in the hydrazinocarbinol (18) or the hydrazonium ion (19).

Thermochemistry of hydroxylammonium and hydrazonium zeolites

Mordenite and zeolite Y were exchanged with hydroxylammonium and hydrazonium ions. The deammination and dehydroxylation reactions were followed using thermoanalytic, mass spectrometric and infrared techniques. The overall acidity of the decationated zeolites was measured by pyridine adsorption.Hydrazonium ions in zeolite Y and mordenite react via thermal decomposition, catalytic dehydrogenation and hydrogenolysis reactions. Hydroxylammonium ions are deprotonated and the base is thermally decomposed as in acid or alkaline solutions. A catalytic dehydrogenation reaction is superimposed.In each case, the NH+4 form is partly obtained and finally the H and dehydroxylated forms of the respective zeolites are formed. The overall acidic properties of the latter two forms are in no way different from a deammoniated-dehydroxylated ammonium zeolite.

The crystal structure of orthorhombic hydrazonium sulphate

Crystalline hydrazonium sulphate exists in two modifications, one orthorhombic and the other monoclinic. The crystal structure of the orthorhombic modification has been determined by the Laue and the rotating-crystal methods. The unit cell, containing four units of the chemical formula, has a-8-251, b-9.159, c-5-532 A. The space group is D~-P2t2121. The atomic co-ordinates were determined by means of Patterson-Harker diagrams and two-dhnensional Fourier syntheses. The sulphate group has the configuration of a nearly regular tetrahedron with the S-O distances 1.48-1.49 A. The O-O distances between different sulphate groups are greater than 3 A. The hydrazonium ion may be considered to be of the trans type, the N-N distance being 1.40 A. One of its nitrogen atoms forms three hydrogen bonds with the N-H. . .O distances 2-73 (two) and 2.77 A., and the other may be regarded as forming three bifurcated hydrogen bonds with the distances 2.79-2.99 A. Besides the oxygen atoms linked by the hydrogen bonds, each N~H6 ++ group has three more oxygen neighbours, the total number of oxygen neighbours surrounding an N~He ++ group being eleven.