Spectrométrie de Masse d'Hétérocycles. VIII—Edude de Dérivés du Dioxasilolanne-1,3,2

The fragmentation mechanisms of 1,3-dioxasilolane have been investigated. These fragmentations lead principally to ‘silyl’ ion formation, or involve cleavage of the bonds α and β to the silicon as for hydrogen migrations.     

Phosphates D'énols: XI—Étude en Spectrométrie de Masse des Dérivés Diméthyliques

The mass spectrometric study of a series of enolic phosphates of type A leades to fragmentation patterns influenced by the nature of the substituents (R, R′ and R″). It is generally observed that a simple or double hydrogen rearrangement occurs with the loss of the enolic groups. When R and R′ are alkyl groups, the migrating groups are the hydrogen atoms on the alkyl group at position 1. When there is no alkyl group at position 1, the hydrogen atoms of the alkyl group at position 2 induce the rearrangement process. Finally, if R, R′ and R″ are hydrogen atoms, the loss of the enolic chain occurs without any rearrangement.     

Substitutions homolytiques intramoléculaires. 17. Décomposition de peroxydes de ϵ-alcényle et de t-butyle. Accès à des tétrahydropyranes substitués

The induced decomposition of t-butyl hex-5-enyl peroxide in good hydrogen donor solvents led to 2-substitude tetrahydropyrans and adduct peroxides. The presence of substituents on the hexenyl moinety influenced seriously the relative ratio of the heterocycle and the adduct peroxide.     

Hétérocycles des Eléments du Groupe IV. VII—Spectrométrie de Masse de Silacyclopentènes

Mass spectra of substituted silacyclopentenes have been studied. The fragmentation mechanisms observed are similar to those for germacyclopentenes. The most important conclusions are retention of the charge on the heteroatom, hydrogen migration, silyl ion formation and expulsion of substituents linked on the heteroatom.     

Mécanismes de Fragmentation en Spectrométrie de Masse par Ionisation Chimique. V–Echanges d'Atomes d'Hydrogène dans les Ions ‘aldehyde protoné’ à Longue Chaine Linéaire

Two different mechanisms for the loss of water from protonated long chain alkyl aldehydes, formed by chemical ionization, have been detected. The first involves a hydrogen exchange between the hydrogen bonded to the oxygen and those of the alkyl chain. This exchange is of lesser importance for aldehydes with less than six carbon atoms. A mechanism for this exchange is postulated. The second mechanism involves a transfer of a hydrogen atom, mainly from positions 3 and 4 of the alkyl chain, to the oxygen and subsequent loss of water.     

Recherches dans la série des cyclitols XLIII. Sur des éthylène-cétals de cétoses dérivés du cyclopentane

The synthesis of a series of keto derivatives of cyclopentane is described. The configurations of these derivatives have been determined by chemical methods and verified by IR. and NMR. spectroscopy. The preferred conformation of the cyclopentane part of the molecule has been established by the study of intramolecular hydrogen bonds and the values of the coupling constants J_{H? C? OH} and J_{H, H}.     

Réactivité de spirochromènes et de mérocyanines azahétérocycliques vis-à-vis de quelques agents nucléophiles

Under the action of nucleophile reagents such as water, hydrogen sulfide and sodium borohydride, the saturated azaheterocyclic spirochromenes are opened either on the azaheterocyclic side or on the benzopyran side or on both parts simultaneously. The merocyanines are either partially reduced or decomposed by the sodium borohydride.     

Spectrométrie de masse. Fragmentations induites par impact électronique d'amino et de diméthylaminopyrimidines

Ekectron-impact mass spectra are presented for some amino and dismethylaminopryimidines. In the two series the base peak is due to the moleculer ion. In the former, the fragmentation pathway invovles loss of hydrogen cyanide from the moleculer ion, whereas in the latter, it is the loss of methyl or methylenimine CH₂?NH that occurs. The presence of HNMe₂⁺ ion for 4-dimethylaminopyrimidine allows one to differentiate this isomer from 2-dimethylaminopyrimidine.     

Étude D'une Série de Phénoxazines et D'azaphénoxazines par Spectrométrie de Masse

Mass spectra of substituted phenoxazines and azaphenoxazines have been determined and are discussed here. These compounds are characterised by hydrogen on the heterocyclic nitrogen and aromatic rings with nitro groups and chlorine as substituents. The fragmentation patterns are explained by known mechanisms. An interpretation of almost all the peaks is offered. The presence of the substituents causes a complete change in the fragmentation patterns compared with the unsubstituted phenoxazine. This is due to changes in charge localisation, caused by the substituents. Isomerisation of the nitro group to the nitroso group gives rise to a particular fragmentation route.     

Liaison hydrogène O-H-O symétrique : II. Spectres de vibration des oxalates acides de lithium hydratés et anhydres

Infrared and Raman spectra of polycrystalline LiHC₂O₄, LiHC₂O₄, · H₂O and their D and ⁶Li containing isotopic derivatives have been investigated at 300 and 90 K in the 4000–50 cm⁻¹ region. All the internal and external optically active modes of lithium hydrogen oxalate monohydrate have been identified and an assignment is given. The spectroscopic data are consistent with X-ray data showing an asymmetric short hydrogen bond with a positive deuterium isotope effect. The dehydration of LiHC₂O₄, · H₂O changes the type of hydrogen bond which becomes symmetric of the double minimum type. The deuteration of LiHC₂O₄, on the other hand. weakens the hydrogen bond and makes it asymmetric again. The asymmetry appears more pronounced at low temperature.     

Utilisation de techniques d'amination réductrice pour la synthèse d'amino-sucres de différents types. Communication préliminaire

Synthesis of amino-sugars using reductive amination reactions. Preliminary communication Treatment of aldehydo- or keto-sugars with primary or secondary amines and hydrogen in the presence of a catalyst (Pd/C) gave with good to excellent yields (67–96%) the expected secondary or tertiary amines. Primary amines can be obtained by using benzylamine, a hydrogenolysis taking place during the reaction.     

Peroxydation du dihydro-2,3 4H pyranne et du dihydro-2,3 furanne. Etude de réactivités

Free radical reactions of unsaturated O-heterocycles with t-butyl hydroperoxide in the presence of cuprous salt gives peroxides. Their analysis leads to the determination of reactivities in H-abstraction. Allylic hydrogen is ten times more reactive than hydrogen in the α position of the heteroatom.     

Structures de deux β-énaminoesters cycliques: l'α-(tétrahydropyrrolidinylidéne-2) acétate d'éthyle et l'α-(hexahydroazepinylidéne-2) acétate d'éthyle

The structure of ethyl α-(tetrahydro-2-pyrrolidinylidene) and α-(hexahydro-2-azepinylidene) acetates has been determined from the X-ray crystallographic analysis. The results show that, in a solid state, these compounds exist as β-enaminoesters which have a Z configuration. They also show the presence of intra and intermolecular hydrogen bonding.     

Spectrographie de Masse de Diazastéroïdes Possédant le Motif Tétrahydroisoquinoléique

We have determined the characteristic fragmentations in a series of 3,4-dihydroisoquinoline and of 8,13 diazaestrones, with the aid of metastable ions, ‘simili’ mass analysed ion kinetic energy spectra (E/V² constant) and some deuterated compounds. In the diazasteroidal series, we could distinguish three essential types of fragmentation, as well as preferential abstraction of the hydrogen situated on the 14-carbon.     

Spectrométrie de Masse d'Hétérocycles Azotés. X–Contribution à l'Etude du Comportement de ll'Ion Aniline et des Ions Aminopyridines avant Fragmentation par Perte de HCN

The study of the mass analysed ion kinetic energy spectra of deuterated derivatives of aniline, aminopyridines and 2-chloro-5-aminopyridine shows that prior to HCN loss, hydrogen scrambling does not occur for aminopyridines and is limited but noticeable for aniline. In the case of this last compound the extent of scrambling varies markedly for small variations in the energy of the ions studied, these variations being within the energy window corresponding to metastable ions. Furthermore, an examination of the mass analysed ion kinetic energy spectra of monodeuterated derivatives of aminopyridines leads to the rejection of the generally accepted mechanism for HCN loss from the molecular ions of these compounds.     

Spectrométrie de Masse d'Hétérocycles Azotés. IX—Structure des Ions [M?CH2CO]+⋅ Formés à Partir des Ions Moléculaires d'Acétamido-2 Benzazoles et mixage d'Hydrogěnes avant leur Fragmentation

It has been established that the loss of ketene from the molecular ions of 2-acetamidobenzothiazole and 2-acetamidobenzimidazole proceeds via a four centre mechanism and gives the corresponding 2-amino-benzazole. For metastable ions with low energy and a long lifetime, hydrogen scrambling occurs before fragmentation through departure of HNC from the 2-aminobenzazole. A mechanism is proposed.     

Fragmentation de la Méthyl-2 Indolizine sous Impact Electronique: perte de H˙ à partir de l'Ion Moléculaire; perte de HCN à partir de l'Ion [M?H˙]+

The origin of the hydrogen radical lost in the ionization chamber from the molecular ion of 2-methylindolizine has been studdied by examination of the spectra of four specifically deuterated species. Hydrogen loss involves preferentially a hydrogen from the methyl substituent but also one of the hydrogens of either ring, especially those of the 5-membered ring. The HCN elimination from the metastable [M? H^˙]⁺ ions was studied using a linked scan method; the results are consistent with loss of identity of all the hydrogen atoms of the precursor ion, which implies an extensive reorganization prior to fragmentation.     

Spectres de masse des composés organiques. 5e communication. Perte de méthane et d'éthylène à partir des ions butyle

The loss of methane and ethylene in the mass-spectrometric fragmentation of different isomeric butyl ions which originate from butyl halides has been studied. The different carbon atoms in n-butyl are already equivalent after 10^?7 s, whereas the statistical distribution of the hydrogen atoms within the molecule can only be observed for the metastable peaks. A protonated cyclobutane structure is proposed as an intermediate product in the fragmentation of the n-butyl ion. The fragmentation of this model has been simulated by a computer. This allows prediction as to the time-scale of fragmentation. The comparison of this model fragmentation with that of isomeric butyl ions shows that, even in the decay of the tertiary butyl ion, the formation of the proposed rearranged cyclic structure competes favorably with the direct fragmentation.     

Cyclisation des amides d'acides phénylthio-1 glyoxaliques avec les dérives carbonylés

The carbonyl-containing compounds react with the amides of phenyl-1-thioglyoxalic acids ( 3 ), and if methyl iodide is present, cause cyclisation into 4-methylthio-5-phenyl-2,5-dihydrooxazol-5-ols ( 4 ). The ketal hydroxyl group of the latter can be methylated. When a hydrogen atom exists in the 2-position (cyclisation with an aldehyde), its elimination provides an oxazole 7 .     

Equilibres conformationnels de glucides au niveau de liaisons s̀ sp2-sp3 C?C. II Dérivés d'hydrozones d'aldéhydo-sucres

A series of alkyl-and aryl-hydrazones of different types of aldehydo-sugars with blocked hydroxy groups have been studied, mainly by PMR. spectroscopy. No traces of the azoalkane or ene-hydrazine forms were detected; the hydrazones were found to exist only in the syn form, except for the cases where an intramolecular hydrogen bond between the ‘amino’ hydrogen of the hydazono group and an oxygen o the glycosyl group provides an extra-stabilization to the anti isomer. Most of these syn hydrazones seem to exist as an equilibrium of the ‘classical’ eclipsed rotamers. The influence of solvent polarity both on configurational and conformational equilibria has been examined. The factors which determine the relative stability of the conformers about a sp²-sp³ s? bond, particularly some kind of non-bonded attraction, are discussed.