Reversible 1,4-cycloaddition of singlet oxygen to N-substituted 2-pyridones: 1,4-endoperoxide as a versatile chemical source of singlet oxygen

N-substituted pyridones (1) easily undergo singlet oxygenation to give exclusively the corresponding endoperoxides (2), which decompose to give pyridones again while liberating 1O2 in high yield.     

Acid catalyzed reduction of nitrosobenzene by 3,5-dipyrrolidinocarbamoyl-N-benzyl-1,4-dihydropyridine as a nadh analog

Acid catalyzed reduction of substituted nitrosobenzenes to the hydroxylamines by 3,5-dipyrrolidinocarbamoyl-N-benzyl-1,4-dihydropyridine has been studied in anhydrous acetonitrile.     

ConjugatedSchiff bases,XIII. sterically congested 1,4-diazabutadienes as dipolar reagents in 1,3-cycloaddition

Use of sterically congested 1,4-diazabutadienes as dipols in reactions with some heterocumulenes has been investigated. A synchronous concerted. mechanism has been considered. The hydantoine-type structure of products has been discussed with respect to their chemical and spectral behaviour.Part XII:Moskal J., Milart P., J. Chem. Res., in press.     

Condensation of aminoferrocene with nitrosobenzene

Summary Phenylazoferrocene and phenylazoxyferrocene were synthesized by the condensation of aminoferrocene with nitrosobenzene in the presence of sodium hydroxide.     

Vapor-phase core photoelectron spectra of para-nitroaniline and nitrosobenzene

Para-nitroaniline (PNA) and nitrosobenzene have been studied in the gas phase by X-ray photoelectron spectroscopy using Al Kα X-ray (1486.6 eV) radia     

[4 + 2]-cycloaddition of alkyl vinyl ethers to 3-aroylpyrrolo-[2,1-c][1,4]benzoxazine-1,2,4-triones

Russian Journal of Organic Chemistry -     

Transition-metal-free synthesis of 1,4-benzoxazepines via [4+3]-cycloaddition of para-quinone methides with azaoxyallyl cations

A formal[4+3]-cycloaddition reaction of ortho-hydroxyphenyl-substituted para-quinone methides(p-QMs)with in-situ generated azaoxyallyl cations is reported.The reaction occurs under very mild reaction conditions(transition-metal free,room temperature,cheap inorganic base)and provides a very efficient route to a series of biologically important 1,4-benzoxazepine derivatives in good to excellent yields.     

Conjugated schiff's bases—10: Control effect of charge resonance coupling on 1,3-cycloaddition of heterocumulenes to some 1,4-diazabutadienes

1,3-Dipolar cycloaddition of organic isocyanates to some 1,4-diazabutadienes has been investigated by theoretical and experimental methods. Analysis of HOMO, LUMO interactions indicated the reaction mechanism and the product structure. Cycloaddition proved to be combined with 1,4 sigmatropic-type hydrogen shift and elimination of the initial 1,4-diazabutadiene fragment.     

Chemical degradation of polystyrene induced by chlorinated nitrosobenzene

Chemically induced degradation of polystyrene (PSt) in the presence of 2,4,6-tri-chloronitrosobenzene (TCNB) as radical generator was investigated in benzene solution by means of the electron spin resonance (ESR) method. The ESR spectra observed after the addition of TCNB to PSt in benzene solution were assigned to the nitroxide radicals (spin adducts) of the PSt radicals,

,

and

. These assignments were deduced from comparisons between observed and computer simulated spectra and were supported by experiments using α-deuterated PSt. It was found by analyses of ESR spectra that two kinds of type (B) radicals were produced, which were different in local conformation. The radicals (A) and (B) were thought to be produced by hydrogen abstraction by the chlorinated phenyl radical which results from homolytic scission of the CN bond of TCNB on slight warming. On the other hand, it was concluded that β-scission of radical (A) results in the formation of the chain scission radical (C). The mechanism of degradation of PSt induced by TCNB as radical initiator is discussed, together with the decrease in molecular weight observed after the addition of TCNB to a PSt-benzene solution. From the decrease of molecular weight it is concluded that TCNB acts as a scission inducer.     

Reaction of nitrosobenzene with 1,2,3,4-tetrachloro-5,5-ethylenedioxycyclopentadiene

The reaction of nitrosobenzene with 1,2,3,4-tetrachloro-5,5-ethylenedioxycyclopentadiene gives rise to N-phenyldichloromaleimide 1 and the unsaturated trichloro-hydroxy-ester-lactam 2.     

On the mechanism of the 1,2-cycloaddition of azobenzenes to ketenimines

The 1,2-cycloaddition of unsymmetrical azobenzenes has been found to be stereoselective and the rate is essentially solvent independent. These observations lead to the postulation of a near concerted process which encounters a steric effect after alignment.     

AOT-based microemulsions accelerate the 1,3-cycloaddition of benzonitrile oxide to N-ethylmaleimide

We studied the 1,3-dipolar cycloaddition of benzonitrile oxide to N-ethylmaleimide in AOT/isooctane/water microemulsions at 25.0 degrees C and found the reaction rate to be roughly 150 and 35 times greater than that in isooctane and pure water, respectively. The accelerating effect of the microemulsion is the combined result of an increase in the local concentrations of the reactants through incorporation into the interface and of the intrinsic rate of the process through electrostatic interactions with the headgroups in the surfactant.     

(2+2)-cycloaddition of triazolinediones to strained bicycloalkenes

Substituted norbornenes and dibenzobarrelene react under forced conditions with $\text{N}$-methyl-1,2,4-triazolin-3,5-diones to afford urazoles via (2+2)-cycloaddition.