Solid-state and solution photocycloadditions of 4-acyloxy-2-pyrones with maleimide

Solid-state photosensitized reactions of 4-acyloxy-2-pyrones (1b,c) with maleimide (2) afforded endo-endo double-[4+2] cycloadducts (3b,c) with high stereoselectivity. Sensitized photoreactions of 1a-d with 2 in solution gave exo-endo double-[4+2] cycloadducts (4a-d). 2-Pyrones 1a-d were photolyzed to give carboxylic acids (5a-d) via their valence isomerization in the solid state and in solution. Such kinds of photoreaction of the 4-acyloxy-2-pyrones were dramatically different from regio- and stereoselective [2+2] cycloadditions of 4-alkyloxy-2-pyrones. The photoreaction mechanisms of 1 with 2 and 1 itself were analyzed by powder X-ray diffraction analysis and MO calculations.     

Dipolar Cycloaddition Reactions with Thiazolonylhydrazones: A New Route for the Synthesis of Several New Thienyl- and Furyl-Thiazolonylpyrrolopyrazole Derivatives of Expected Biological Activities

Several new pyrrolopyrazoles were synthesized via the reactions of each of 2-thiophenecarboxaldehyde thiazolonylhydrazone or 2-furaldehyde thiazolonylhydrazone with N -substituted maleimides followed by partial dehydogenation using bromobenzene and complete aromatization using nitrobenzene. Structures were established on the basis of elemental analyses and spectroscopic data studies.     

Chiral squaramides catalyzed diastereo- and enantioselective Michael addition of α-substituted isocyanoacetates to N-aryl maleimides

An efficient diastereo- and enantioselective Michael addition of α-substituted isocyanoacetates to N-aryl maleimides catalyzed by quinine or cyclohexane-1,2-diamine derived squaramide catalysts has been disclosed, affording the corresponding adducts in good yields (up to 99%), high diastereoselectivities (up to >20:1 dr) and good to excellent enantioselectivities (up to 94% ee) under mild conditions.     

On the reactivity of isoindolo[2,1-a]quinazoline-5-ones

Base- and acid-catalyzed nucleophilic addition of 11H-isoindolo[2,1-a]quinazoline-5-one to aromatic aldehydes and maleimides was investigated. The aldol adducts and condensation products were obtained stereoselectively. Main diastereomers of the Michael adducts were isolated in 74-89% yield, and converted by N-methylation to new stable α-substituted isoindole derivatives, for which 6-methylisoindolo[2,1-a]]quinazoline-5-one stands as the unsubstituted reference. The stability of the latter was monitored in moist aerated CDCl₃ solution, and one of the oxidative hydrolysis product was characterized by X-ray diffraction analysis as the corresponding N-arylphthalimide. The reactivity of the unsubstituted 6-methylisoindolo[2,1-a]]quinazoline-5-one was also investigated with acetylenic Michael acceptors. Fully conjugated isoindole derivatives possessing an original pull-push-pull structure were obtained. The conformations and molecular orbitals of the dibenzoylacetylene adduct were studied at the DFT level of theory. Its static quadratic hyperpolarizabilty β₀ was also calculated at the ZINDO level.     

N-取代基马来酰亚胺均聚合研究进展

N-取代基马来酰亚胺聚合物具有良好的热性能,近些年来随着材料性能的要求提高,对这类单体的研究也越来越多,本论文综述了N-取代基马来酰亚胺在自由基、阴离子聚合、配位聚合等方面的均聚合研究进展。     

[3+2]- Versus [4+2]-cycloaddition reactions of 3-methylsulfanyl-2-arylazo-3-(pyrrolidin-1-yl)acrylonitriles with N-substituted maleimides involving pyrrolidine-derived azomethine ylides

3-Methylsulfanyl-2-arylazo-3-(pyrrolidin-1-yl)acrylonitriles do not enter into [4+2]-cycloaddition reactions with maleimides to form the expected pyrrolo-pyridazines. Instead the formation of novel pyrrolo-pyridazines of type 4 takes place via a formal [3+2]-cycloaddition of initially formed pyrrolidine-derived azomethine ylides 7. The mechanism leading to the final product is discussed.     

Benzo[f]isoindole derivatives from cycloaddition reaction of 2,4-dimethylpyrimido[2,1-a]isoindole and maleimides

In contrast to the previously reported results in the reaction of maleimides with pyrido[2,1-a]isoindole and 1,2-bis substituted isoindoles, the reaction between 2,4-dimethylpyrimido[2,1-a]isoindole and maleimides leads to the formation of unusual products. Their structure is assessed by NMR and mass spectrometry. An original reaction pathway is proposed. The high quantum yields observed in fluorescence opens the route to applications as biological probes. To cite this article: Z.V. Voitenko et al., C. R. Chimie 9 (2006).     

Copper-catalyzed synthesis of oxime ethers from iminoxy radical (CN–O) and maleimides via radical addition

An efficient Cu(II)-catalyzed radical addition of maleimides has been achieved. The identified copper catalyst enables the formation of oxime radicals (N–O) by cleaving the O–H bond in ketoximes, followed by the radical addition to N-substituted maleimides. The oxime radicals (N–O) were detected and confirmed by EPR spectroscopy and variable-temperature ¹H NMR. The simple one-pot reaction realizes the facile preparation of a variety of oxime ether adduct products in moderate to good yields.     

Efficient asymmetric Michael reaction of 2-oxindole-3-carboxylate esters with maleimides catalyzed by cinchonidine

A highly efficient enantioselective Michael reaction of 2-oxindole-3-carboxylate esters with N-maleimides catalyzed by commercially available cinchonidine was described. The desired adducts, containing a quaternary center at the C3-position and a vicinal tertiary center, were obtained in excellent yields (up to 99%), good enantioselectivities (up to 85% ee), and diastereoselectivities (dr>90:10) in the presence of 0.05–5 mol % catalyst loading.     

Synthese von neuen bifunktionellen Maleinimidverbindungen zur Herstellung von Chemoimmunokonjugaten

Summary Bifunctional maleimide compounds are suitable for binding small molecules to carrier proteins in that they bind to the sulfhydryl group of proteins through the double bond of the maleimide group and to molecules of low molecular weight (e.g. anticancer drugs) through a functional groupX. 18 maleimide compounds of the general formula Maleimid-R-X (R=phenylene, benzyl-, methylene-, ethylene, or am-benzoylethylamide group andX=hydroxy-, amino-, hydrazino-, carboxylic acid-, carboxylic anhydride-, carboxylic acid chloride-, carboxylic acid hydrazide-, oxycarbonylchloride-, aldehyde, keto-, orp-toluenesulfonate-group) were synthesized and characterized through¹H- and¹³C-NMR-spectroscopy, elemental analysis, and mass spectrometry.