Beitrag zum Mechanismus der stossinduzierten Fragmentierungen von quaternären Stickstoffverbindungen. 2. Mitteilung über stossinduzierte Fragmentierungen von felddesorbierten Kationen

Mechanistic studies on the collision-induced fragmentations of quaternary ammonium ions The collision-induced fragmentation behaviour of field desorbed quarternary ammonium ions has been investigated. A main reaction of these ions is the cleavage of the N? C bond accompanied by hydrogen rearrangement, i.e. alkane loss from the tetraalkyl substituted ammonium ions of the iodides 1, 2 and 3 , respectively, Deuterium labelling indicates that the hydrogen transfer to the leaving group occurs to the extent of about 80% from the α-position and about 20% from the other positions of an alkyl group. Pronounced heterolytic cleavage of the N? C bond is observed in the benzyl substituted ammonium ion of 4 . The β-phenylethyl substituted ammonium ion of 5 shows a homobenzylic heterolysis, possibly yielding the phenonium ion j.     

Massenspektrometrische Untersuchungen der Gasphase über CrCl3 und CrCl3/Cl2

Mass Spectrometric Investigations of the Vapor Phase over CrCl₃ and CrCl₃/Cl₂ The vapor in the system CrCl₃/Cl₂ is investigated by Knudsen-cell mass spectrometry in the temperature range between 770 and 910 K. The gaseous molecules CrCl_{3, g} and CrCl_{4, g} are identified mass spectrometrically; the molar heats of formation are determined by 2nd law calculations. CrCl_{3, g}: Δ_fH(298) = ?79.2 kcal; CrCl_4,g: Δ_fH(298) = ?103.2 kcal; the composition of the vapor in equilibrium with condensed CrCl_3,s, CrCl_2,s is calculated (Temperature 773–1273 K).     

Massenspektrometrische Untersuchungen der Gasphase über As2O5

Mass Spectrometric Investigations of the Gaseous Phase above As₂O₅ The gaseous phase above solid As₂O₅ has been investigated in the temperature range between 862 and 939 K by mass spectrometric methods. The presence of gaseous As₄O_x-molecules (6 ≤ × ≤ 10) and O₂ was proved. Using the partial pressures, heats of formation (Δ_fH°(900), kJ · mol^?1; 2nd law calculations) were calculated (As₄O_7,g: -1209,5; As₄O_8,g: -1361,9; As₄O_9,g: -1495,4; As₄O_10,g: -1618,8). The enthalpy of formation of solid As₂O₅ was determined to be Δ_fH°(298) = ?1007,9 kJ · mol^?1. The thermochemical data of the As₄O_x-molecules are discussed in context with possibilities for the synthesis of solid As₄O₁₀.     

Photoinduzierte Reaktionen von 3-Phenyl-2H-azirinen mit Carbonsäureestern 40. Mitteilung über Photoreaktionen

Irradiation (280–350 nm light) of a benzene solution of 3-phenyl-2H-azirines 1a – e in the presence of carboxylate esters, whose carbonyl groups are activated by electron withdrawing groups situated in the acyl or alkyl moiety, produces 5-alkoxy-3-oxazolines (Tab. 1 and 4, Scheme 2) isolated in 18–82% yield. These heterocycles undoubtedly originate by regiospecific addition of the ester carbonyl group to the azirine-derived benzonitrile-methylide ‘dipole’ (Scheme 1). The 5-(2,′ 2′, 2′-trifluoroethoxy)-3-oxazolines, derived from 2′, 2′, 2′-trifluoroethyl carboxylic esters, on treatment with methanolic hydrogen chloride at low concentration, are smoothly transformed into the corresponding 5-methoxy-3-oxazolines (e.g. 16 → 17 , Tab. 5). Utilizing this process, various hitherto relatively unknown 9. 5-alkoxy-3-oxazolines become accessible. The constitution of the adducts is based essentially on spectral data. The structure of trans-5-methoxy-2,4-diphenyl-5-trifluoromethyl-3-oxazoline (trans- 14 ), the addition product of methyl trifluoroacetate and the benzonitrile-benzylide from 2,3-diphenyl-2H-azirine ( 1d ), was determined by X-ray crystallography (Section 5). Benzonitrile-isopropylide ( 22 ), resulting from the photochemical transformation of 2,2-dimethyl-3-phenyl-2H-azirine ( 1a ), also reacts with S-methyl thiobenzoate to give 2,2-dimethyl-5-methylthio-4,5-diphenyl-3-oxazoline ( 26 ). Ethyl cyanoacetate protonates predominantly the dipolar species derived from 1a at the nitrile C-atom and yields after work-up ethyl α-cyano-cinnamate ( 29 ) and ethyl isopropylidene-cyanoacetate ( 30 ) (Scheme 4). The relative rate of addition (k_rel) of benzonitrile-isopropylide ( 22 ) to methyl α-haloacetates and dimethyl oxalate was determined by competition experiments (Section 6). Log k_rel correlated satisfactorily (r = 0.97) with the pK_a of the acide derived from the ester reactant: log k_rel = ? 1.72 pK_a + 2.58 or with Taft's substituent constants σ*: log k_rel = 2.06 σ* ? 4.11 [k_rel(methyl dichloroacetate) = 1; Section 7.1]. On the basis of the results obtained, the mode of reaction of the so-called benzonitrile-methylide ‘dipole’ is discussed and a model for the transition state of addition of ester-carbonyl groups is proposed that accounts for the observed regiospecifity and steroselectivity.     

Dampfdruckmessungen und massenspektrometrische Untersuchungen der Gasphase über Erdalkalimetallhalogeniden

Vapor Pressure and Mass Spectrometrical Measurements of Gaseous Phase of Alkaline Earth Halides Vapor pressures and vapor compositions of molten alkaline earth halides were measured by Knudsen effusion method and mass spectrometry, respectively. The enthalpies of dissociation of strontium and barium halides were calculated from appearance potentials of alkaline earth ions M′⁺. Temperature dependence of vapor pressure and enthalpies of vaporization are given. The vapor over molten alkaline earth halides contains only small amounts (max. 1.9%) of dimeric molecules.     

Photochemische Erzeugung und Reaktionen des Benzonitril-benzylids. 42. Mitteilung über Photoreaktionen

Photochemical Generation and Reactions of Benzonitrile-benzylide The low temperature irradiation of 2,3-diphenyl-2H-azirine ( 1 ) in DMBP-glass at ?196° has been reinvestigated. It was possible to convert 1 nearly quantitatively into the dipolar species benzonitrile-benzylide ( 3 , Φ₃ = 0,78), which exhibits UV.-absorptions at 344 (? = 48000) and 244 nm (? = 28500) (Fig. 1, Tab. 1). Irradiation of 3 with 345 nm light at ?196° resulted in almost complete reconversion to the azirine 1 (Φ = 0,15; Fig. 2). When the solution of 3 in the DMBP-glass was warmed up to about ?160° a quantitative dimerization to 1,3,4, 6-tetraphenyl-2,5-diaza-1,3,5-hexatriene ( 8 ) occurred. This proves that 8 is not only formed by the indirect route 3 + 1 → 7 \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\longrightarrow }\limits^{hv} $\end{document} 11 → 8 known before (Scheme 1), but also by dimerization of 3 either by direct head to head coupling or via the intermediate e (p. 2675), followed by a fast thermal hydrogen transfer reaction. The occurrence of the dipolar intermediate 11 in the photochemical conversion of the bicyclic compound 7 to 8 could also be demonstrated by low temperature experiments: On irradiation at ?196° 7 gave the cherry red dipolar intermediate 11 (λ_max = 520 nm), which at ?120° isomerizes to 8 . It should be noted, that neither 7 nor 11 are formed by dimerization reactions of 3 . Experiments carried out at room temperature demonstrate, that both processes for the formation of 8 may compete: Irradiation of a solution of 1 (DMBP, c = 8 × 10^?4 to 5 × 10^?3M ) with 350 nm light of high intensity (which does not excite the bicyclic compound 7 ) leads to a relative high photostationary concentration of the dipolar species 3 . Under these conditions the formation of 8 is due to dimerization of 3 (Φ₈ = 0,19). With low light intensity only a very low stationary concentration of 3 can be obtained. Therefore the reaction of 3 with 1 , leading to the bicyclic intermediate 7 , becomes now predominant (Φ_?1 = 1,55, which corresponds with the expected value of 2 × 0,8). Irradiation of 1 at ?130° with 350 nm light of high intensity gives 8 with a quantum yield of 0,44. This is in agreement with the theoretical value Φ₈ = 0,4 for an exclusive formation of 8 by dimerization of 3 . The lower quantum yield for the formation of 8 at room temperature makes probable that under these conditions 3 not only dimerizes to 8 , but also to another, so far unidentified dimer, e.g. 2,3,5,6-Tetraphenyl-2,5-dihydropyrazine. By flash photolysis of a solution of 1 (cyclohexane, c = 10^?4M , 25°) the disappearance of 3 could directly be measured by UV.-spectroscopy: At relative high concentrations (c ≥ 10^?7M ) 3 disappeared according to a second order reaction with the rate constant k = 5 × 10⁷M ^?1S ^?1. At lower concentrations (c ≤ 10^?7M) the rate of disappearance of 3 follows first order kinetics. The rate constant of this pseudo first order reaction ( 3 + 1 → 7 ) has been determined to be 1 → 10⁴M^?1S^?1. Using Padwa's table of relative rates for the cycloaddition of the dipolar species 3 to various dipolarophiles, including the azirine 1 , an absolute rate constant of k ≈ 8 × 10⁸M ^?1S ^?1 for the addition of 3 to the most active dipolarophile fumaronitrile could be estimated. In cyclohexane at room temperature, the diffusion controlled rate constant equals 6,6 × 10⁹M ^?1S ^?1. In Table 1 the UV.-maxima of several nitrile-ylides, among them a purely aliphatic one, are given.     

Reaktionen von Bleitetraacetat mit alicyclischen Alkoholen,III. Cyclopropyl- und Cyclobutylcarbinole. 18. Mitteilung über Reaktionen mit Bleitetraacetat

When treated with lead tetraacetate, cyclopropylcarbinol and cyclopropylmethylcarbinol do not give β-fragmentation products resulting from the intermediate formation of cyclopropyl radicals; however, cyclopropylmethylcarbinol affords a small amount of a fragmentation product which arises from C_α? C_β bond cleavage involving removal of a methyl radical. In contrast, cyclobutylcarbinol undergoes β-fragmentation in 18% yield with formation of both the unrearranged cyclobutyl acetate and the rearranged cyclopropylmethyl acetate. These results suggest the following order of increasing radical stability: cyclopropyl < methyl < cyclobutyl, whereas the isolation of the isomeric fragmentation acetates in the lead tetraacetate reaction of cyclobutylcarbinol represents further evidence that in the β-fragmentation process the initially produced carbon radical fragment is in major part oxidized to the corresponding carbonium ion before final product formation.     

Stereospezifische Fragmentierungen in den Massenspektren von Cyclohexandiaminen und Bis(aminomethyl)cyclohexanen. 33. Mitteilung über massenspektrometrische Untersuchungen,,

Stereospecific Fragmentations in the Mass Spectra of Cyclohexanediamines and Bis(aminomethyl)cyclohexanes The mass spectral behaviour, especially loss of NH₃, of the six isomeric cyclohexanediamines 1--3 (cis and trans each, Scheme 1) as well as of the six isomeric bis(aminomethyl)cyclohexanes 4--6 (cis and trans each, Scheme 6) has been investigated. The cis- and trans-compounds of the 1,2-isomers 1 and 4 show very similar spectra, because of the ease of ring cleavage at C(1)–-C(2) and the similar geometrical relations in all ring conformations. The cis- and trans-compounds of both the 1,3- and 1,4-isomers 2, 3, 5 and 6 show striking differences in their mass spectra due to stereospecific elimination of NH₃ from the molecular ion.     

Die Aminoalkylierung von Chinazolinen und Chinazolonen mit Hilfe der GRIGNARD-Reaktion. 5. Mitteilung über GRIGNARD-Reaktionen mit Halogenalkyliminen [2]

Quinazoline is aminoalkylated at C(4) by 3-dimethylaminopropyl-magnesium-chloride in preparative yield to give 3 , and by oxidation 5 , just as aryl and alkyl-magnesiumbromide give 15 , 19 , and 22 . These 4-substituted quinazolines yield by further treatment with the same GRIGNARD compound by 3, 4 or 1, 2-addition 3, 4-di-hydro-quinazolines ( 12 , 16 ) and 1, 2-dihydro-quinazolines ( 13 , 17 , 20 , 23 ), the latter being formed exclusively when the 4-position in the quinazoline is occupied by bulky residues; only the later can be oxidised to give 2,4-disubstituted aromates (cf 14 , 18 , 21 , 24 ). The spectroscopic and physicochemical behaviour of the dihydro compounds and the aromatic and the aromatic compounds are discussed.     

Reaktionen von Glutaminsäuredimethylester im Massenspektrometer. 21. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

The mass spectral fragmentation of dimethyl glutamate ( 1 ) and its deuterated derivatives 1a , 1b and 1c has been investigated. By loss of a methoxycarbonyl group from the molecular ion an ion of m/e 116 is generated. The latter splits off methanol (m*), the resulting fragment of m/e 84 giving raise to the base peak of the spectrum. Only part of the hydrogen transferred to the leaving group originates from thc amino group, as was suggested earlier [2] [3]. Basing on experiments with deuterated compounds we propose an additional mechanism for the reaction, i.e. hydrogen transfer from C(3) to methoxyl. The fragment generated by both processes is most likely to be a pyrrolinonium ion. Thermal side reactions in the mass spectrometer (formation of pyroglutamic acid ester) followed by fragmentation may lead to the same ion. – The mechanisms discussed are supported by the mass spectral fragmentation of N-acetyl-glutamic acid diesters 3 , 3a , 3b and 3d and of the N, N-dimethyl derivatives 4 and 4a . – The fragmentation reactions investigated are similar to some of 1,3-trimethylenediamine derivatives [7]. This means that there are parallels in the mass spectral fragmentation of difunctional compounds irrespective of the nature of the functional groups.     

Katalytische Effekte bei den Reaktionen von 2,4-Dinitrofluorbenzol und 2,4-Dinitrochlorbenzol mit p-Anisidin in Benzol. 5. Mitteilung über nucleophile aromatische Substitutionsreaktionen

(1) The rates of the reactions of 2.4-dinitrofluorobenzene and 2.4-dinitrochlorobenzene with p-anisidine have been measured in benzene solution, with and without the addition of pyridine and 1.4-diaza-[2.2.2]-bicyclooctane (DABCO) as catalysts.     

Zur synthese von 3,4-dihydro-2H-1,4-benzoxazin-2- und 3-carbonitrilen. II. Mitteilung über studien zur chemie der 1,4-oxazine

Reaction ofo-aminophenols la, lb and lc with alkeyl dibromopropionates selecrively leads to 2-substitured dihydro-1,4-benzoxazines. This high regioselectivity is explained by initial elimination of hydrogen bromide from the dibromopropionate to from a reactive Michael acceptor, which cyclized to the benzoxazines 3a, 3b and 3c after Michael addition to the amines 1. This mechanism is proven by reaction of the amines la-ld with the Michael acceptor 15 to yield the 2-carbonitriles 16a-l6d. Substitution of the methoxyl group in 18 by cyanide leads to the 3-carbonitrile 19.     

Massenspektrometrische Identifizierung und Synthese isomerer und homologer Spermidin- und Spermin-Derivate. 25. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen. 161. Mitteilung über Alkaloide

Synthesis of isomeric and homologous spermidine and spermine derivatives and their identification by mass spectrometry. The structure of homologous and isomeric spermidines and spermines follows from mass-spectroscopical analysis of their peracetyl (see text, footnote 3) (Table 1) or tosyl-acetyl (Table 2) derivatives. In the case of the peracetyl compounds, triads of peaks are recorded which, according to the number of methylene groups between the nitrogen atoms, show mass numbers characteristic for each of the substances (Scheme 1, ions b , d , e and c ). On the basis of cyclic ions of type f (Scheme 2), occurring in the mass spectra of N-acetyl derivatives, tosylated on a secondary amino nitrogen atom, deductions can be drawn as to the number of methylene groups between neighbouring tosylated and acetylated nitrogen atoms in these compounds.     

Thermisch und photochemisch induzierte intramolekulare, 1,3-dipolare Cycloadditionen von 5-(2-Allyloxyphenyl)-2-phenyltetrazol. Vorläufige Mitteilung. 54 Mitteilung über Photoreaktionen

Thermal and Photochemically Induced Interamolecular 1,3-Dipolar Cycloaddition Reactions of 5-(2-Allyloxyphenyl)-2-phenyltetrazole The title compound 5 is easily obtained by a recently described procedure (Scheme 2). The tetrazole 5 reacts at 165–170° or on irradiation at room temperature to yield 2-phenyl-3,3a-dihydrochromano[4,3-c]pyrazole ( 7 , Scheme 3), which probably arises by intramolecular [3+2]-cycloaddition of the intermediate nitrilimine. Dehydrogenation of 7 with chloranil leads to 2-phenylchromano[4,3-c]pyrazole ( 8 , Scheme 3).     

Photochemie von in 4-Stellung substituierten 5-Methyl-3-phenyl-isoxazolen.44. Mitteilung über Photoreaktionen

Photochemistry of 4-substituted 5-Methyl-3-phenyl-isoxazoles. 4-Trideuterioacetyl-5-methyl-3-phenyl-isoxazole ([CD₃CO]- 27 ), upon irradiation with 254 nm light, was converted into a 1:1 mixture of oxazoles [CD₃CO]- 35 and [CD₃]- 35 (Scheme 13). This isomerization is accompagnied by a slower transformation of ([CD₃CO]- 27 ) into [CD₃]- 27 . Irradiation of the isoxazole derivatives 28, 29, 30 and (E)- 31 yielded only oxazoles 36, 37, 38 and (E), (Z)- 39 ; no 4-acetyl-5-alkoxy-2-phenyl-oxazole, 2-acetyl-3-methyl-5-phenyl-pyrrole or 2-acetyl-4-methoxycarbonyl-3-methyl-5-phenyl-pyrrole, respectively, were formed (Scheme 9 and 10). Similarly (E)- 32 gave a mixture of (E), (Z)- 40 only (Scheme 11). Upon shorter irradiation, the intermediate 2H-azirines (E), (Z)- 41 could be isolated (Scheme 11). Photochemical (E)/(Z)-isomerization of the 2-(trifluoro-ethoxycarbonyl)-1-methyl-vinyl side chain in all the compounds 32, 40 and 41 is fast. At 230° the isoxazoles (E)- and (Z)- 32 are converted into oxazoles (E), (Z)- 40 . The same compounds are also obtained by thermal isomerization of the 2H-azirines (E), (Z)- 41 . The most probable mechanism for the photochemical transformations of the isoxazoles, as exemplified in the case of the isoxazole 27 , is shown in Scheme 13. A benzonitrile-methylide intermediate is postulated for the photochemical conversion of the 2H-azirines into oxazoles. 2H-Azirines are also intermediates in the thermal isoxazole-oxazole rearrangement. It is however not yet clear, if the thermal 2H-azirine-oxazole transformation involves the same transient species as the photochemical reaction. A mechanism for the photochemical isomerization of the 2H-azirine 11 to the oxazole 15 is proposed (Scheme 3).     

Katalytische Effekte bei den Reaktionen von 2, 4-Dinitrofluorbenzol mit Benzylamin und N-Methylbenzylamin in Benzol. 6. Mitteilung über nucleophile aromatische Substitutionsreaktionen

• (1) The rates of reaction of 2,4-dinitrofluorobenzene with benzylamine and with N-methylbenzylamine have been measured in benzene solution, with and without the addition of pyridine or 1, 4-diaza-bicyclo[2.2.2]octane (DABCO) as catalyst.
• (2) Both reactions are catalyzed by the reacting amine, by pyridine and by 1, 4-diaza-bicyclo[2.2.2]octane.
• (3) Whereas the dependence on base concentration is linear in the case of N-methyl-benzylamine, the rate constants are curvilinearly related to base concentration in the reaction with benzylamine. Steric effects are shown to be responsible for this different behaviour, which is easily understood in terms of the two-step intermediate mechanism (eq.1) for nucleophilic aromatic substitutions.
• (4) Part of the pyridine catalysis has to be attributed to a medium effect, as can be shown directly in the reaction involving benzylamine.
• (5) The sensitivity of both reactions to base catalysis is much greater than that of the reaction of piperidine with 2, 4-dinitrofluorobenzene, but is found to be considerably smaller than in the reaction of p-anisidine with the same substrate, thus suggesting a correlation between the basicity of the reacting amine and the sensitivity of the reaction to base catalysis.