Cycloaddition reactions of nitrosoalkenes and azoalkenes with cyclopentadiene and other dienes

Faragher, Roy; Gilchrist, T. L.

doi:10.1039/p19790000249

Cited by 82 publications

(19 citation statements)

References 3 publications

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“…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). Several theoretical calculations of nitrosoethylenes have been reported (28)(29)(30), but none of these have examined the cis and trans isomerization.…”

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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“…Flash column chromatography was performed with silica gel 60 (0.035–0.070 mm) provided by Acros Organics, as the stationary phase. 2,2′‐(Propane‐2,2‐diyl)difuran ( 3 ), 1‐(2‐bromo‐1‐phenylethylidene)‐2‐(2,4‐dinitrophenyl)hydrazine ( 10b ), 1‐(2,4‐dinitrophenyl)‐3‐phenyl‐1,4,4a,7a‐tetrahydrofuro[3,2‐ c ]pyridazine ( 12b ), 1‐(2,4‐dinitrophenyl)‐4a,6‐dimethyl‐3‐phenyl‐1,4,4a,7a‐tetrahydrofuro[3,2‐ c ]pyridazine ( 12j ), cis ‐3‐[1‐(2,4‐dinitrophenyl)‐3‐phenylpyrazol‐5‐yl]prop‐2‐enol ( 24a ), cis ‐3‐[1‐(2,4‐dinitrophenyl)‐3‐phenylpyrazol‐5‐yl]prop‐2‐en‐1‐yl 2,2,2‐trifluoroacetate ( 24b ), 2‐bromo‐1‐(4‐nitrophenyl)ethanone oxime ( 28a ), 2‐bromo‐1‐(4‐fluorophenyl)ethanone oxime ( 28b ) and 2‐bromo‐1‐(4‐methoxyphenyl)ethanone oxime ( 28c ) were prepared as described in the literature.…”

Section: Methodsmentioning

confidence: 99%

Hetero‐Diels–Alder and Ring‐Opening Reactions of Furans Applied to the Synthesis of Functionalized Heterocycles

et al. 2017

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Furans have been explored as a scaffold for the synthesis of a range of heterocyclic compounds, exploring their dienophilic behaviour towards nitroso‐ and azoalkenes as the first step. Acid‐catalysed rearrangements of these cycloadducts, 4a,7a‐dihydro‐4H‐furo[2,3‐e][1,2]oxazines and 1,4,4a,7a‐tetrahydrofuro[3,2‐c]pyridazines, were studied. Using 1 equiv. of TFA, the bicyclic heterocycles derived from furan and 2‐methylfuran were converted into furans bearing side‐chains incorporating oxime and hydrazone groups by ring‐opening of the six‐membered ring with the concomitant aromatization of the furan ring. The use of TFA as solvent led to rearrangement via spirocyclic intermediates, followed by furan ring‐opening to afford functionalized isoxazoles or pyrazoles. Furthermore, furo‐oxazines derived from 2,5‐dimethylfuran, in which furan aromatization is precluded, were converted efficiently into 6H‐1,2‐oxazines through a furan ring‐opening reaction upon thermolysis in the presence of a catalytic amount of p‐toluenesulfonic acid. The tetrahydrofuro[3,2‐c]pyridazines derived from furan and dimethylfuran underwent acid‐catalysed addition reactions, leading to 6‐substituted hexahydrofuro[3,2‐c]pyridazines, when in the presence of alcohols or water.

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“…173 ± 177 Apparently, the range of cycloaddition reactions of nitrosoalkenes to C=C bonds is not exhausted by the data presented above. Thus Gilchrist et al 18,93 believe that the reaction of a-halo oximes with enamines in the presence of Na 2 CO 3 involves generation and subsequent [4+2]-cycloaddition of nitrosoalkenes to electron-rich C=C bonds. 18,93 However, the alkylation of enamines with a-bromo oximes 152,153 in the absence of bases should apparently be regarded as direct S N 2 substitution of bromine, because the intermediate immonium salts can be isolated.…”

Section: Compoundmentioning

confidence: 99%

Conjugated nitrosoalkenes

Lyapkalo¹,

Ioffe²

1998

Russ. Chem. Rev.

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Published data on the preparation, structure, physical and chemical properties, and reactivity of nitrosoalkenes are described systematically. The influence of the structure and stereoelectronic effects of substituents at the double bond on the stability of nitrosoalkenes is analysed. Primary attention is paid to concerted cycloaddition of nitrosoalkenes to miscellaneous multiple bonds, in particular, to the problems of regio-, stereo-, and enantioselectivity of [4 + 2]-cycloaddition of nitrosoalkenes to alkenes. The bibliography includes 183 references.

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Cycloaddition reactions of nitrosoalkenes and azoalkenes with cyclopentadiene and other dienes

Cited by 82 publications

References 3 publications

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

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

Hetero‐Diels–Alder and Ring‐Opening Reactions of Furans Applied to the Synthesis of Functionalized Heterocycles

Conjugated nitrosoalkenes

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