Darstellung und Eigenschaften von Drei stabilen monomeren Nitrosoolefinen

Höbold, W.; Prietz, Ursula; Pritzkow, W.

doi:10.1002/prac.19693110210

Cited by 22 publications

(17 citation statements)

References 6 publications

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“…Results are tabulated in Table 3. Nitrosoalkenes have been isolated, but only when there are bulky substituents at the P-carbon (26). Simple nitrosoalkenes such as nitrosoethylene have only been observed in solution and (or) trapped with various reagents (27,28).…”

Section: \ H I S-cismentioning

confidence: 99%

Experimental and theoretical investigation of C-nitroso rotation in 2-nitrosoimidazoles

1988

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Can. J . Chem. 66, 3044 (1988). I-Methyl-2-nitrosoimidazole exhibits broadened 'H nuclear magnetic resonance signals at room temperature. The concentration independency of this spectrum as well as the linearity of the 700-nm absorbance with concentration rules out equilibrating nitroso monomer -nitroso dimer. It is suggested that there are equilibrating s-cis and s-trans nitroso monomer rotational isomers. At -59°C two sets of signals in a 3:l ratio are observed. Analysis of CH3 chemical shifts in terms of the magnetic anisotropy of the nitroso group suggests that the s-trans is the major isomer. The broadening observed at higher temperatures leads to a barrier for rotation (from the trans isomer) of 12.4 kcal mol-'. Ab initio calculations with 2-nitrosoimidazole using the 3-21G basis set show that the fully planar s-cis and s-trans forms are minima, with the s-trans more stable by 2.5 kcal mol-', and a barrier to rotation (from the s-trans) of 13.0 kcal mol-'. These results are in good agreement with those from solution phase. Various factors suggest that the .rr conjugative interaction between the nitroso group and imidazole ring is relatively unimportant. JUDY L. BOLTON, MICHAEL R. PETERSON et ROBERT A. MCCLELLAND. Can. J. Chem. 66, 3044 (1988). Le mtthyl-1 nitroso-2 imidazole prtsente en tnlargissement des signaux de rtsonance magnetique nucleaire du 'H a la temperature ambiante. L'absence de relation entre le spectre et la concentration aussi bien que la relation de proportionnalite existant entre la concentration et I'absorption ii 700 nm tcartent la posibilite d'un Cquilibre monomere nitroso -dimere nitroso.On suggkre qu'il y a un tquilibre entre les isomkres rotationnels s-ciset s-trans du monomkre nitroso. On observe a -59°C deux groupes de signaux dans un rapport 3:l. L'analyse des dCplacements chimiques en fonction de l'anisotropie magnktique du groupe nitroso suggkre que l'isomkre s-trans est majoritaire. L'Clargissement des signaux observe plus haute temptrature conduit a une barrikre 2 la rotation de 12.4 kcal mol-' (pour l'isomkre bans). Les calculs ab initio effectues avec le nitroso-2 imidazole en utilisant l'ensemble de base 3-2 IG montrent que les formes totalement planes s-cis et s-trans sont minimales. La forme S-bans est plus stable de 2.5 kcal mol-' avec une barribre a la rotation de 13.0 kcal mol-'. Ces resultats s'accordent parfaitement avec ceux obtenus en solution. Divers facteurs suggkrent qu l'interaction .rr conjuguee entre le groupe nitroso et le cycle imidazole joue un r61e relativement peu important.[Traduit par la revue]Extensive studies of the 2-nitroimidazole radiosensitizers as has been characterized for nitrosobenzenes (14)(15)(16)(17). This have revealed a number of biological and biochemical effects paper presents our examination of this phenomenon, at both the that are associated with reductive metabolism (1-6). The experimental and theoretical level. As will be shown, our initial implication is that biological reduction is producing some premise was incorrect. The nrnr ...

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Section: \ H I S-cismentioning

confidence: 99%

Experimental and theoretical investigation of C-nitroso rotation in 2-nitrosoimidazoles

1988

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“…This principle of 1,4-elimination using organic or inorganic bases has been long known and the transient appearance of nitrosoalkenes has sometimes been detected by the presence of a blue or green coloration [8]. Isolation of nitrosoalkenes, however, has only been achieved in a limited number of cases [5] [9] [lo] ( Table 1).…”

Section: Discussionmentioning

confidence: 99%

Nitrosoalkenes: Synthesis and Reactivity

Francotte

Merényi

Vandenbulcke-Coyette

et al. 1981

Helvetica Chimica Acta

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SummarySome (1-and 8-halonitrosoalkenes 1 have been synthesized and characterized. The halogen atoms of the oxime precursors 2 can be substituted by alkoxy groups. Two kinds of cycloaddition reaction of 1 have been observed: i) reaction of the NO group with dienes gives 3,6-dihydrooxazine derivatives 6 which isomerise to epoxyepimines 7 in most cases of 8-substituted nitrosoalkenes: ii) if 4,5-dihydrooxazines 22 are obtained, the cycloaddition of the nitrosoalkenes as 4 7r-component is presumed.Nitrosoalkenes possess a large synthetic potential, since they comprise both an alkene activated by an electron withdrawing group and an 1,3-diene system. Furthermore, the nitroso group itself reacts with it wide number of reagents [l] and allows an easy, simultaneous incorporation of nitrogen and oxygen by addition We have recently reported the epoxy-epimination of cyclic 1,3-dienes by isomerization of the cycloadducts formed from such dienes with certain halonitrosoalkenes [6] [7]. This reaction merits particular attention since nitrosoalkenes are readily accessible, highly reactive intermediates which can be used in situ. In order to study the scope and limitations of this stereospecific reaction, which allows the functionalization of the four sp2-centres of a diene in one step, it seemed interesting to vary the dienes and the substituents of the nitrosoalkene.') Taken in part from the Ph. D-Thesis of E. Francotte (l078), present address: C'iha-Geigy AG, Zentrale Forschung. CH-4002 Basel.0018-019X/81/4/1208-11$01.00/0 0 198 I Schweizer-ische Chemiache Gesellschaft

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“…In our earlier work [4] we did not succeed in determining the configuration of the 1-aryl-2-nitroso prop-1-enes prepared, and it remained uncertain whether a stabilization of the compounds by mesomerism of the nitroso olefin group with the aromatic nucleus takes place. The position and the extinction coefficient of the n-r* band in the region of about 700 nm seemed to be arguments for a stabilization of these nitrosoolefins by mesomerism with the aromatic nucleus.…”

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“…Monomeric nitrosoolefins can be isolated only in the absence of strong nucleophiles and if their structure makes both a rearrangement and a polymerisation impossible. So we succeeded in the preparation of three 2,6disubstituted 1-phenyl-2-nitroso prop 1-enes [4], and later the isolations of 1-nitroso 2,2-di-tert-butyl ethylene [5] and 1,ldichloro-2-nitroso prop-1-ene [6] were also accomplished.In our earlier work [4] we did not succeed in determining the configuration of the 1-aryl-2-nitroso prop-1-enes prepared, and it remained uncertain whether a stabilization of the compounds by mesomerism of the nitroso olefin group with the aromatic nucleus takes place. The position and the extinction coefficient of the n-r* band in the region of about 700 nm seemed to be arguments for a stabilization of these nitrosoolefins by mesomerism with the aromatic nucleus.…”

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Structure of monomeric 1-aryl-2-nitroso-prop-1-enes

Engel

Pritzkow

Gelbrich³

et al. 1995

J. Prakt. Chem.

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Nitrosoolefins are unstable intermediates in nucleoplilic substitutions at bischloronitroso compounds and a-chlorooximes [ l -31. They react rapidly with nucleophilic agents; in the absence of such agents they rearrange by a proton shift to oximes of &$-unsaturated carbonyl compounds. A further possible reaction of monomeric nitrosolefins is the polymerisation to tarry compounds. Monomeric nitrosoolefins can be isolated only in the absence of strong nucleophiles and if their structure makes both a rearrangement and a polymerisation impossible. So we succeeded in the preparation of three 2,6disubstituted 1-phenyl-2-nitroso prop 1-enes [4], and later the isolations of 1-nitroso 2,2-di-tert-butyl ethylene [5] and 1,ldichloro-2-nitroso prop-1-ene [6] were also accomplished.In our earlier work [4] we did not succeed in determining the configuration of the 1-aryl-2-nitroso prop-1-enes prepared, and it remained uncertain whether a stabilization of the compounds by mesomerism of the nitroso olefin group with the aromatic nucleus takes place. The position and the extinction coefficient of the n-r* band in the region of about 700 nm seemed to be arguments for a stabilization of these nitrosoolefins by mesomerism with the aromatic nucleus. On the other hand the substituents in 2-and 6-position of the phenyl group make a coplanar arrangement of the aromatic ring and the nitrosolefin system very improbable.We have once again prepared the nitrosoolefins lbd described in [4] and moreover 1-(2,6-dimethylphenyI)-2nitroso prop-1-ene l a in order to elucidate their structure by X-ray analysis. Only in the case of 1-(2-methoxy-4,6-1 Formula Scheme 1 Structure of 1-(2-methoxy-4,6-dimethylphenyl)-2-nitroso prop-1-ene Id. The plane of the nitrosoolefin side chain is twisted out of the plane of the aromatic nucleus with an angle of (49.3 i 0.2)". Table 1 13C-and 'H-nmr signals of the nitrosoolefins la-d Ar\ /CH3 1 b Ar : 2,4,64rirnethylphenyI

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Darstellung und Eigenschaften von Drei stabilen monomeren Nitrosoolefinen

Cited by 22 publications

References 6 publications

Experimental and theoretical investigation of C-nitroso rotation in 2-nitrosoimidazoles

Experimental and theoretical investigation of C-nitroso rotation in 2-nitrosoimidazoles

Nitrosoalkenes: Synthesis and Reactivity

Structure of monomeric 1-aryl-2-nitroso-prop-1-enes

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