Die Produkte der Thermolyse von N-(1-Pyridinio)-2-nitroaniliden sind keine Triaziridine,sondern 1, 2-Bis[(2′-nitrophenyl)-azoxyl]-benzole

The products of the thermolysis of N-(1-pyridinio)-2-nitroanilides ( 1 ) had previously been interpreted as tris (2-nitrophenyl)-triaziridines ( 3 ). The present work shows them to be actually 1, 2-bis[(Z)-(2′-nitrophenyl)-ONN-azoxy]benzenes ( 5 ). The revised structural assignment is based on the chemical and the spectroscopic (especially ¹H-NMR.) properties of 5 and on the results of a X-ray structural analysis.     

Phthalimido-nitren I. Bleitetraacetat-Oxydation von N-Aminophthalimid in inerten Lösungsmitteln. Bildung und Eigenschaften von trans-1,4-Bisphthaloyl-2-tetrazen

Lead tetraacetate oxidation of N-aminophthalimide ( 11 ) in inert solvents gives as major products phthalimide ( 15 ) or trans-1,4-bisphthaloyl-2-tetrazene ( 12 ), the former ( 15 ) on slow, the latter ( 12 ) on fast addition of the oxidizing agent. As by-products are found: (a) in the presence of acetic acid: N-acetylamino-phthalimide ( 14 ), and (b) in its absence (especially at higher temperatures): benzocyclobutenedione ( 13 ) along with N-phthalimido-phthalimide ( 16 ) as well as traces of phthalic anhydride ( 17 ). The tetrazene 12 and phthalimide ( 15 ) are considered to be formed by oxidation and fragmentation, respectively, of the intermediate 1,4-bisphthaloyl-tetrazane ( 18 ). Phthalimido-nitrene ( 22 ), or its conjugated acid 23 , is postulated to be the species which initiates the major reactions, namely: (a) addition to the educt 11 to give the tetrazane 18 and (b) fragmentation with loss of N₂ to give the dione 13 . The minor by-products 16 and 17 may be the result of cross-amidation of 11 with 15 and rearrangement-oxidation via phthalazine-1,4-dione ( 30 ), respectively. The structure of the tetraacyltetrazene 12 follows from its properties, among others a comparison of its UV. spectrum with that of the known 1,4-dimethoxycarbonyl-1,4-dimethyl-2-tetrazene ( 32 ). Methanolysis of 12 affords 1,4-di-(o-methoxycarbonyl-benzoyl)-2-tetrazene ( 33 ). The diacyltetrazene 33 is converted to methyl N-methoxycarbonyl-anthranilate ( 36 ), N₂ and phthalimide ( 15 ) on thermolysis, or to methyl N-acetylphthalamate ( 35 ), methyl N, N′-carbonyldianthranilate ( 37 ) and methyl N-acetyl-anthranilate ( 38 ) on acetylation in pyridine. The intermediate in these reactions, leading to 36 , 37 and 38 , probably is o-methoxycarbonyl-phenylisocyanate ( 34 ), itself the result of a Curtius-type rearrangement. Acetolysis of the tetrazene 12 gives phthalimide ( 15 ), N₂ and N-carboxyanthranilic anhydride ( 42 ) by a mechanism analogous to that of the methanolysis of 12 . In the preparation of 1,4-dimethoxycarbonyl-1,4-dimethyl-2-tetrazene ( 32 ), required for the above mentioned comparison, by zinc reduction of methyl N-methyl-N-nitro-carbamate ( 43 ), followed by bromine oxidation of methyl N-amino-N-methylcarbamate ( 44 ), a deamination of 43 to methyl N-methyl-carbamate ( 45 ) was observed both in the reductive and in the oxidative step. Both formations of 45 can be formulated via a nitrene and a tetrazane, namely via 47 and 48 .     

Azimine IV. Kinetik und Mechanismus der thermischen Stereoisomerisierung von 2,3-Diaryl-1-phthalimido-aziminen

Azimines IV. Kinetics and Mechanism of the Thermal Stereoisomerization of 2,3-Diaryl-1-phthalimido-azimines¹) Mixtures of (1E, 2Z)- and (1Z, 2E)-2-phenyl-1-phthalimido-3-p-tolyl-azimine ( 3a and 3b , resp.) and (1E, 2Z)- and (1Z, 2E)-3-phenyl-1-phthalimido-2-p-tolylazimine ( 4a and 4b , resp.) were obtained by the addition of oxidatively generated phthalimido-nitrene (6) to (E)- and (Z)-4-methyl-azobenzene ( 7a and 7b , resp.). Whereas complete separation of the 4 isomers 3a, 3b, 4a and 4b was not possible, partial separation by chromatography and crystallization led to 5 differently composed mixtures of azimine isomers. The spectroscopic properties of these mixtures (UV., ¹H-NMR.) were used to determine the ratios of isomers in the mixtures, and served as a tool for the assignment of constitution and configuration to those isomers which were dominant in each of these mixtures, respectively. Investigation of the isomerization of the azimines 3a, 3b, 4a and 4b within the 5 mixtures at various concentrations by ¹H-NMR.-spectroscopy at room temperature revealed that only stereoisomers are interconverted ( 3a ? 3b; 4a ? 4b) and that the (1E, 2Z) ? (1Z, 2E) stereoisomerization is a unimolecular reaction. These observations exclude an isomerization mechanism via an intermediate 1-phthalimido-triaziridine (2) or via dimerization of 1-phthalimido-azimines (1) , respectively. The 3-p-tolyl substituted stereoisomers 3a and 3b isomerized slightly slower than the 3-phenyl substituted ones 4a and 4b , an effect which is consistent with the assumption that the rate determining step of the interconversion of (1E, 2Z)- and (1Z, 2E)-1-phthalimido-azimines (1a ? 1b) is the stereoisomerization of the stereogenic center at N(2), N(3), either by inversion of N(3) or by rotation around the N(2), N(3) bond. The total isomerization process is assumed to occur via the thermodynamically less stable (1Z, 2Z)- and (1E, 2E)-isomers 1c and 1d , respectively, as intermediates in undetectably low concentrations which stay in rapidly established equilibria with the observed, thermodynamically more stable (1E, 2Z)- and (1Z, 2E)-isomers 1a and 1b , respectively. At higher temperatures, the azimines 3 and 4 are transformed into N-phenyl-N,N′-phthaloyl-N′-p-tolyl-hydrazine (8) with loss of nitrogen.     

Dass Hydrierprodukt eines β-Nitro-N-nitrosoamins ist kein 1,2,3-Triazolidin,sondern ein β-Hydroxylamino-N-nitrosoamin

The Product of Hydrogenation of a β-Nitro-N-nitrosoamine Is Not a 1,2,3-Triazolidine, but a β-Hydroxylamino-N-nitrosoamine It is shown, by spectroscopy, that the product of catalytic hydrogenation of N, 2-dimethyl-2-nitro-N-nitrosopropylamine (1) consists of a 5:1 mixture of (E)- and (Z)-2-hydroxylamino-N, 2-dimethyl-N-nitrosopropylarnine (3) and does not contain - as had been claimed - any l, 2-dihydroxy-1, 2, 3-triazolidine (2). Thus there is still no evidence for the existence of the N(OH)N(OH) functionality. The structure of intermediates on the way to 1 are also revised.     

1-Amino-2-phthalimido-diazen-1-oxide: Bildung,Eigenschaften und Fragmentierungen in Imido- und Amino-nitrene

1-Amino-2-phthalimido-diazene-1-oxides: Formation, Properties and Fragmentation Reactions into Imido- and Amino-nitrenes¹) Oxidatively generated phthalimido-nitrene ( 1 ) reacts with the nitrosoamines 2a-d (see Scheme 1) to give the corresponding (Z)-1-amino-2-phthalimido-diazene-1-oxides 3a-d in good yields. With the O-nitroso compound 2e , no addition of the nitrene 1 took place. The constitution the adducts 3 (R = NR′₂) is deduced from their spectroscopic properties (UV., IR., ¹H-NMR. and MS.) as compared to those of (Z)-1-aryl- and (Z)-1-alkyl-2-phthalimido-diazene-1-oxides 3 (R = aryl and alkyl, resp.). The (Z)-configuration of 3 (R = NR′₂) follows from an X-ray analysis which is reported separately. Compounds 3 (R = NR′₂) are cleaved photolytically as well as by acid to the corresponding nitrosoamines 2 (R = NR′₂) and the nitrene 1 , which could be trapped by cyclohexene to give 40% of 7-phthalimido-7-azabicyclo [4.1.0]heptane ( 8 ) and by dimethylsulfoxide to yield 96% of S, S-dimethyl-N-phthalimido-sulfoximide ( 13 ). Nucleophilic attack leads to fragmentation of 3 (R = NR′₂) into derivatives of phthalic acid and degradation products of intermediate aminonitrenes 24 corresponding to the respective nitrosoamines 2 (R = NR′₂) with loss of oxygen. A general rationalization for the formation of 24 includes as a key step of N- to C-migration of the O-atom (see Scheme 6). The final fate of 24 is depending on the type of the nucleophile used. Thus, hydrazinolysis of 3b and of 3c generates besides N, N′-phthaloylhydrazine ( 15 ), morpholine ( 14 ) from 3b and 1, 3-dihydroisoindole ( 16 ) together with 6′-methylidene-1, 2, 3, 4-tetrahydronaphthalene-2-spiro-1′-cyclohexa-2′, 4′-diene ( 17 ) from 3c (see Scheme 5). Treatment of 3b and of 3c with sodium methylate leads in both reactions to monomethyl phthalate ( 33 ) and, with 3b , to 1, 2-dimorpholinodiazene ( 31 ) and, with 3c , to 17 (see Scheme 7). Finally, the reaction of 3b with diethylamine generates N, N-diethylphthalamic acid ( 36 ), morpholine ( 14 ), 1,1,4,4-tetraethyl-2-tetrazene( 34 ) and l,l-diethyl-4,4-(3-oxapentamethylene)-2-tetrazene ( 35 ) (see Scheme 8).     

Novel Synthesis of Agaritine,a 4-Hydrazinobenzyl-Alcohol Derivative Occurring in Agaricaceae

The 4-hydrazinobenzyl alcohol ( 3 was prepared (58%)) by diiobutylaluminiumhydride reduction of methyl 4-hydrazinobenzoate ( 4 ), whereas LiA1H₄ or LiBh₄ reduction of 4 proceeded further to yield (via intermediate 3 ) (4-tolyl)hydrazine ( 5 ). The alcohol 3 was stable under O₂-free conditions and exhibited no tendency to eliminate H₂O, neither thermally nor with H⁺ catalysis. Oxidation of 3 with SeO₂ yielded 4-(hydroxymethyl)benzine-diazonium ion ( 8 ), identified by its azo coupling product 9 with 2-naphthol. Condensation of 3 with 1-benzyl 5-Hydrogen N-(benzyloxycarbonyl)-L-glutamate ( 10 ) in presence of dicyclohexylcarbodiimide afforded 81% of N²-(benzyloxycarbonyl)-L- glutamic acid 1-(benzyl-ester) 5-{2-[4-(hydroxymethyl)phenyl]hydrazide} ( 11 ) which upon controlled hydrogenolysis (quinoline-sulfur-poisoned Pd/C catalyst) gave 82% of L-Glutamic acid 5-{2-[4-(hydroxymethyl)phenyl] hydrazide} ( 1 ), i. e. agaritine, a metabolite of Agaricus bisporus. Without poisoning of the catalyst, hydrogenolysis of ( 11 ) yielded L-glutamic acid 5-[2-(4-tolyl)hydrazide] ( 12 ).     

Triaziridine 7. Mitteilung. Stabile pyramidale Konfigurationen an den Stickstoff-Atomen von Dialkyl-und Trialkyl-triaziridinen

Stable Pyramidal configurations at the Nitrogen Atoms of Dialkyl-and Trialkyl-triaziridines Stereochemical features of the recently synthesized nine samples of di- and trialkyl-triaziridines, namely the 1,3-cyclopentylen-(series a ) and the two stereoisomers of the diisopropyl derivatives (series b and c ), containing as the third substituent an H-atom ( 2 ), a CH₃ group ( 3 )or a CH₂OH group ( 4 ), were elaborated on the basis of the ¹H-, ¹³C-, and ¹⁵N-NMR spectra. The three N-atoms of the saturated N₃-homocycle were found to be stable to pyramidal inversion in all cases. According to their NMR spectra, 2 – 4 of the series a and b possess twofold symmetry (C_s), while 2 – 4 of series c are asymmetric. Thus, series c has the trans-configuration at N(2)/N(3) and, consequently, the cis-configuration at N(1)/N(2), while series a and b have the cis-configuration at N(2)/N(3) and -since the all-cis-arrangement is excluded-the trans-configuration at N(1)/N(2). The asymmetry of the trans-configurated 2c turned into twofold symmetry (C₂), when a little CF₃COOH was added. The ¹H- and ¹³C-NMR data of series b and c of our alkyl-triaziridines exhibit a shielding effect, according to which there are two types of i-Pr groups, i-Pr(a) and i-Pr(b). They differ in the NMR signals of the H- and the C-atoms of their CH groups: the H-atoms of i-Pr(a) are more deshielded by 0.75–1.111 ppm and its C-atoms are more shielded by 10.0–160.0 ppm as compared to the corresponding atoms of i-Pr(b). i-Pr(a) is cis (on the N₃-homocycle) to a large substituent (such as i-Pr, Me, CH₂OH) and to a lone pair, while i-Pr(b)is cis only to a small (H) or to no substituent and to one or two lone pairs. An analogous effect appears in the NMR signals of the CH₃ and CH₂OH groups at N(1) of 3 and 4 in the series b and c .     

An experimental analysis of fluctuating temperature measurements using hot-wires at different overheats

Adjacent parallel hot-wire anemometers at different temperatures have sometimes been used to measure fluctuating temperatures in turbulent flows. This work presents an extensive experimental comparison of temperatures measured with a parallel-wire probe to temperatures simultaneously measured with a standard cold-wire probe. The results show the parallel-wire probe to work well in low intensity flows with temperature signals which are not too small. However, the parallel-wire probe temperature measurements are not accurate for high turbulence intensities or for small temperature signals, and in general the cold-wire system is probably to be preferred.     

«Push-Pull»-Acetylene als Hilfsmittel zur Synthese von Amiden

Amide Synthesis by Means of ‘Push-Pull’-Acetylenes ‘Push-Pull’-acetylenes react easily with carbon acids, Addition of amines to the crude reaction mixture gives amides in an excellent yield by a simple one-pot procedure. Because of the high selectivity of the acetylenes 1 towards carboxylic functions and of the high selectivity of the enol esters 4 towards amine functions, ‘push-pull’-acetylenes could be excellent reagents for peptide synthesis.