Fragmentation de Quelques Hydrazines,Tétrahydrocinnolines et Pyrazolidines sous I'Impact Electronique

The mass spectra of various hydrazines, tetrahydrocinnolines and pyrazolidines, prepared by the condensation of a diazenium cation or its conjugated base with olefins, are discussed. The main fragmentation mode of trisubstituted hydrazines corresponds to a retroaddition process which produces the diazenium cation and the olefin. Another fragmentation mode involves breaking of the N? N bond which is due to a charge localization in the phenyl ring the latter being substituted on a nitrogen atom in all the hydrazines studied. This N? N bond split is dominant in the fragmentation of tetrahydrocinnolies. On the other hand, its does not appear in the spectra of pyrazolidines. The latter mainly undergo a dipolar-1, 3 retroaddition-like process giving the protonated form of the azomethine imine used in thier synthesis.     

Photoreduction de la benzophenone par des phtalimidines et des dihydro isoquinolones: Etude chimique par RMN PNIC

Benzophenone is photoreduced by pthalimidines and dihydro isoquinolones. The hydrogen atom α to the nitrogen atom is abstracted and radical coupling leads to adducts. CIDNP studies of these adducts show inversion of polarisation for the adduct on the N-alkyl chain when the nitrogen is bound to a benzylic methylene. This inversion is explained by considering that the radical on the N-alkyl chain derives from the radical on the ring.     

Synthese et etude par resonance magnetique nucleaire du carbone 13 et de l'etain 119 d'une serie de triorganostannyl-2 butanes

Optically active triorgano-2-stannylbutanes have been synthetized by different methods, one being the direct substitution of optically active s-butyl halides with triorganostannyl alkali metals. This route involves a complete or partial inversion of configuration at the chiral carbon atom. Carbon-13 and tin-119 NMR data are reported as support for the identification of eight triorgano-2-stannylbutanes. The special case of tetra(2-butyl)tin, with four identical chiral centres has been examined.     

N,N-Coupled heterobicycles from cyclic hydrazine derivatives. Part 6 . Electron ionization mass spectrometry of some substituted 1-thiocarbamoyl and 1-carbamoylpyrazolidines

The electron ionization mass spectra of six substituted 1-thiocarbamoyl and four substituted 1-carbamoyl-pyrazolidines were measured and carefully analyzed. The fragmentation pathways were elucidated by metastable ion analysis and exact mass measurement. The principal fragmentations were the same for all the compounds studied. The related importance of different decomposition channels, however, varied according to the structure of the compounds. Some substituents also prompted fragmentations unique to them. The most important reaction was the loss of the thiocarbamoyl or carbamoyl substituent with simultaneous hydrogen atom migration from the (thio)carbamoyl nitrogen to the ring nitrogen giving rise to ionized pyrazolidine at m/z 72. In this process for 1-(N-arylthiocarbamoyl)pyrazolidines the charge tended to remain with the substituent part of the molecule. Moreover for all the compounds studied [M-2H]^+. ion peaks formed by dehydrogenization of the original compounds were observed.     

Crystallographic report: The crystal structure of bis‐(3,3‐dimethyl‐3,4‐dihydro‐2H‐1‐thia‐4a,9‐diaza‐3‐sila‐fluorene) silver nitrate

The title compound is a silver nitrate complex with two molecules of 2‐mercaptobenzimidazole derivative. The silver atom lies on an inversion centre of the crystal lattice; nitrogen of the nitrate anion is in another inversion centre. Bond length Ag(1)? N(7) is 2.087(3) Å. Copyright © 2005 John Wiley & Sons, Ltd.     

Rare example of nucleophilic substitution at vinylic carbon with inversion: mechanism of methyleneaziridine formation by sodium amide induced ring closure revisited

Intramolecular nucleophilic substitution of the C-Br bond of (E)- and (Z)-2-bromobut-2-enylamines by the pendant nitrogen atom leads to 2-ethyleneaziridines by way of stereochemical inversion at the vinylic carbon atom. The stereochemistry of the products is unambiguously established by X-ray crystallography performed on two derivatives. These cyclizations represent some of the first examples of substitution with inversion in unactivated vinylic substrates. In conjunction with additional deuterium-labeling experiments, the accepted mechanism for this reaction is shown to be flawed.     

A practical ruthenium-catalyzed cleavage of the allyl protecting group in amides, lactams, imides, and congeners

A convenient methodology for the deprotection of N-allylic amide-like moieties was developed. The first examples accounting for the ruthenium-catalyzed deallylation of amides, lactams, imides, pyrazolidones, hydantoins, and oxazolidinones have been achieved by the sequential use of Grubbs carbene (isomerization step) and RuCl(3) (oxidation step). A variety of substrates, including enantiopure multifunctional beta- and gamma-lactams, can be employed.     

Z,E-isomerization mechanism for N-arylthio-1,4-benzoquinonimines: DNMR and DFT investigations

Z,E-isomerization has been investigated for the series of the N-arylthio-1,4-benzoquinonimines using a line shape analysis in the (1)H NMR spectra. Thermodynamic parameters and substituent effects have been analyzed for the isomerization process. It has been shown based on the DFT (B3LYP) calculations that the dynamic transformation for N-arylthio-1,4-benzoquinonimines should be considered as a combination of the two different processes, a rotation about the N-S bond and an inversion at nitrogen via the transition state with the linear C=N-S moiety. The free energies of activation for the isomerization (DeltaG(298 K)) measured experimentally depend on the substitution in the quinonimine moiety and phenyl ring and can be referred either to the inversion of the nitrogen atom or to the hindered rotation about the N-S bond.     

Etude dans la serie des organogallylazoles I. Synthese et structure

A series of N-dimethylgallylazoles have been prepared by treatment of azoles (imidazoles, benzimidazoles, pyrazoles, s-triazole and benzotriazole) with trimethylgallium.The structure (monomeric, dimeric, polymeric) of the resulting compounds depends on the position of the nitrogen atoms in the azole moiety. In the case of pyrazolyl derivatives, the NMR study in acetone or acetonitrile shows the existence of an equilibrium between the monomeric and dimeric forms.     

Thermodynamic and electron-transfer properties of copper(II/I) polyaminothiaether complexes

In electron-transfer reactions, the change in the oxidation states of the reactants is generally accompanied by structural changes, which influence the electron-transfer kinetics. Previous studies on the systems of Cu(II)/(I) complexes involving cyclic tetrathiaether ligands indicated that inversion of coordinated donor atoms is a major geometric change during the overall electron-transfer process. Complex formation and isomerization studies on complexes with the 1,4,8,11-tetraazacyclotetradecane ligand have demonstrated that a necessary condition for conformational change is deprotonation followed by inversion of coordinated N atoms. When one or more nitrogen donor atoms in a ligand are replaced with sulfur, there is a choice of N or S inversion. It has been hypothesized that donor atom inversion (N or S donors) is a major factor that can lead to conformationally limited electron-transfer kinetics of copper systems. In the current study, the thermodynamic properties, electron-transfer kinetics and conformational changes in copper(II)[1,4,8-trithia-11-azacyclotetradecane], copper(II)[1,8-dithia-4,11-diazacyclotetradecane] and copper(II)[1,11,-dithia-4,8-diazacyclotetradecane] were determined in order to determine the effect of inversion of coordinated N atoms on electron-transfer rates as a function of low concentrations of water in an aprotic solvent (acetonitrile). By using controlled amounts of water as a hydrogen ion acceptor, deprotonation of amine nitrogen and nitrogen donor inversion was followed by comparing self-exchange rate constants for reduction and oxidation of the copper complexes. Data on thermodynamic properties and electron-transfer kinetics are presented. Possible conformational changes and kinetic pathways for complexes with ligands having mixed N and S donor sets are presented.     

La condensation sur les olefines de deux dipoles-1,3 issus de l'oxydation electrochimique des dimethyl-1,1 et dibenzyl-1,1 (dinitro-2,4 phenyl)-2 hydrazines. : Modes de reaction et reactivites

The action of triethylamine on the solutions of the electrochemically prepared 1,1-dimethyl or 1,1-dibenzyl-2-(2,4-dinitrophenyl) diazenium cations gives the corresponding azomethine-imine 1,3-dipoles by deprotonation of the alkyl group. These two dipoles react readily with electron-rich double bonds but not with electron-poor double bonds. Their condensation reaction gives pyrazolidines in a concerted and regioselective fashion. A qualitative interpretation based on a perturbational frontier orbital treatment model is given to explain the 1,3-dipole reactivity and stereochemistry.     

Design of a new rotary molecular machine based on nitrogen inversion: a DFT investigation

Ab initio calculations are employed to investigate nitrogen inversion as a configuration change that can supply an extremely useful switchable control mechanism for some complex systems. In this paper, the design of a new artificial rotary molecular machine based on nitrogen inversion is discussed. The introduced design of a molecular rotator is based on the reciprocating motion of a substituent due to the inversion phenomenon, leading to the rotary motion in the molecule. Since simple secondary amines easily face the inversion process at room temperature, aziridine is selected as the initial driver for the molecular motion. The most obvious finding from this study is that, following the displacement of the substituent attached to the aziridine nitrogen atom, two rotary motions occurr in the molecule, one clockwise and another counterclockwise with a 39.52° to 150.09° angle domain.     

Electronic interaction between the nitrogen,oxygen, and silicon atoms in the molecules of α-aziridin-1-ylalkoxy(triethyl)silanes

By the PMR method we have established the existence of a high frequency of the inversion of the nitrogen atom in the molecules of -aziridin-1-ylalkoxysilanes. This is due to the fact that the high (because of p-d bonding with the silicon atom) electronegativity of the oxygen atom in the Si-O-C-N system makes possible an interaction between the unshared electron pair of the nitrogen atom and the antibonding orbital of the C-O bond. The latter, in its turn, increases the degree of p-d bonding between the oxygen and silicon atoms (in these compounds the order of the Si-O bond is greater than in the alkoxysilanes).     

新的二[4-对甲基苯基-3，5-二(2-吡啶基)-1，2，4-三氮唑]双硫氰根合锰配合物的合成，晶体结构和磁性(英)

本文合成了一个新的含有4-对甲基苯基-3，5-二(2-吡啶基)-1，2，4-三氮唑配体(L)的锰(Ⅱ)配合物，[MnL₂(NCS)₂]。其结构由X射线晶体学，红外和电喷雾离子质谱表征。在晶体结构中, 锰原子有一反演中心并由2个三芳基三氮唑配体的4个氮原子和2个反式硫氰根的2个氮原子八面体配位。磁性测定表明在75～300 K的温度范围内该配合物是顺磁性的。     

Raman and infrared spectra, ab initio and DFT calculations, and vibrational assignments for 2,3-cyclopentenopyridine

The structural properties of 2,3-cyclopentenopyridine (pyrindan) have been investigated using several spectroscopic and computational techniques. The Raman and infrared spectra of the molecule have been recorded and a full vibrational assignment was proposed on the basis of experimental and theoretical results. The vapor-phase Raman spectrum was successfully obtained at 260 degrees C without sample decomposition. Density functional theory (DFT) and M?ller-Plesset (MP2) calculations predict that the presence of the nitrogen atom in the six-membered ring has almost no effect on the barrier to inversion (587 cm(-1)) and puckering frequency (139 cm(-1)) as compared to the values previously determined (488 cm(-1) and 143 cm(-1)) for the indan molecule.     

Recherches en serie azabenzodiazepine—VIII : Hydrazinolyses d'azabenzodiazepinones et d'azabenzodiazepinethiones de type 1,5

The action of hydrazine on several azabenzo-1,5-diazepinones gives 3(5)-methyl-5(3) pyrazole and the corresponding heterocyclic diamines but the reaction with phenylhydrazine is more complicated and depends on the nature of the heterocycle attached to the seven member ring. In this case two reaction centres must be taken into account; the amide group and the carbon atom in the 6 position. According to experimental conditions hydrazinolysis of s-triazolotriazepinethiones and pyrazolodiazepinethiones give either 5-hydrazino s-triazolotriaze-pines or pyrazolylamino-triazole (or pyrazole) or 3-hydrazinopyrazoles and 3,4-diamino triazole. The mechanism suggested is addition of molecules of hydrazine in the 5 position followed by a transannular reaction to the 7 position.     

Experimental and computational study of intermolecular migration of N,N-dimethylcarbamoyl group from N(7) to N(1) on a 7-azaindoline derivative

N,N-Dimethylcarbamoylation of the anilinic nitrogen atom N(1) on the spiro 7-azaindoline consists of two steps. The first step is N,N-dimethylcarbamoylation of the pyridyl nitrogen atom N(7), leading to the formation of an isolable intermediate. The second step is intermolecular migration of the N,N-dimethylcarbamoyl group from the pyridyl nitrogen atom N(7) to the anilinic nitrogen atom N(1). We accomplished optimization of the reaction conditions based on the revealed reaction mechanism and a large scale synthesis of compound 3 in quantitative yield.     

Syntheses of 1-alkyl-2-acylindoles, 1-alkyl-2-acylindole-3-carboxylic acids,and their esters,in superbasic media

2-Acylindoles and 2-acylindole-3-carboxylic acids are readily alkylated at the nitrogen atom by haloalkanes in a superbasic medium (DMSO + NaOH). For the carboxylic acids, this reaction may proceed either entirely at the nitrogen atom, or at both the the nitrogen atom and the carboxyl group, depending on the content of water in the medium and the alkali -haloalkane ratio.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 472–482, April, 1996.     

Triazènes et benzotriazines dérivés de sucres

Sugar triazenes and benzotriazines Several triazenylsugars have been prepared, generally in good yields, by treating an amino sugar with a substituted benzenediazonium salt. The triazenylsugars bearing a hydrogen atom on the triazenyl group are acetylated on the nitrogen atom closest to the glycosyl moiety (N(1)), even when the proton exchanged sites between N(1) and N(3). When an acetyl or a methoxycarbonyl group was present in the ortho position of the benzene ring cyclization took place leading to a 3,4-dihydro-4-methylidene-1,2,3-benzo[d]triazine or a 3,4-dihydro-1,2,3-benzo[d]triazin-4-one respectively.     

Syntheses and Characterizations of Two Palladium(II) Complexes of 5‐Mercapto‐1‐methyltetrazole

Reaction of PdCl₂(CH₃CN)₂ with the sodium salt of 5‐mercapto‐1‐methyltetrazole (MetzSNa) in methanol solution affords an interesting dinuclear palladium complex [Pd₂(MetzS)₄ ] ( 1 ). However, treatment of PdCl₂(CH₃CN)₂ with neutral MetzSH ligand in methanol solution produces a mononuclear palladium complex [Pd(MetzSH)₄]Cl₂ ( 2 ). Both complexes were characterized by IR, ¹HNMR, UV‐Vis spectroscopy as well as X‐ray crystallography. Single‐crystal X‐ray diffraction analyses of two complexes lead to the elucidation of the structures and show that 1 possesses an asymmetric structure: one Pd atom is tetracoordinated by three sulfur atoms and one nitrogen atom to form PdS₃N coordination sphere, the other Pd atom is tetracoordinated by three nitrogen atoms and one sulfur atom to form PdSN₃ coordination sphere. The molecules of 1 are associated to 1‐D infinite linear chain by weak intermolecular Pd···S contacts in the crystal lattice. In 2 , the Pd atom lies on an inversion center and has a square‐planar coordination involving the S atoms from four MetzSH ligands. The two chloride ions are not involved in coordination, but are engaged in hydrogen bonding.