Presence Of N-phenylmaleimide Research Articles

Thermal transformations of alk-1-enyl-N-phthalimidoaziridines

Thermolysis of alk-1-enyl-N-phthalimidoaziridines leads to products of 1,5-electrocyclization of intermediate azomethine ylides with participation of C=C bonds. If acyl or alkoxycarbonyl substituent is present in the aziridine ring, the C=O bond is also involved. Thermolysis of the title compounds in the presence of N-phenylmaleimide or dimethyl acetylenedicarboxylate under analogous conditions gives products of 1,3-dipolar cycloaddition of azomethine ylides to the double or triple bond of the dipolarophile.

Intra- and intermolecular thermal transformations of 2-acyl- and 2-alkoxycarbonyl-N-phthalimidoaziridines

Heating 2-acyl- and 2-alkoxycarbonyl-N-phthalimidoaziridines leads to substituted oxazoles in 45-65% yield. Only esters of oxazolecarboxylic acids are formed when the aziridine contains acyl and alkoxy groups. The thermolysis of the same aziridines in the presence of N-phenylmaleimide and the dimethyl ester of acetylenedicarboxylic acid gives both oxazoles and the products of 1,3-dipolar cycloaddition from aziridines with two substituents at the carbon atoms but only oxazoles from trisubstituted aziridines.

ChemInform Abstract: The Generation of Metaphosphoramidates by Fragmentation of 2,3- Oxaphosphabicyclo(2.2.2)octene Derivatives.

Abstract Phosphole oxides with N,N-diethylamino, N-mesitylamino and N-tert-butylamino substituents on phosphorus were generated in the presence of N-phenylmaleimide to give Diels-Alder adducts with the 7-phosphanorbornene framework. Products were characterized by 31P and 13C NMR spectroscopy, and in one case by 17O NMR spectroscopy. Insertion of oxygen into a P[sbnd]C bond of this strained cyclic system occurred smoothly on treatment with m-chloroperbenzoic acid. The resulting derivatives with the 2,3-oxaphosphabicyclo[2.2.2]octene ring system were characterized by 1H, 31P, and 13C NMR spectroscopy. In the case of the N-mesityl derivative, two stable isomers were formed and separated by chromatography. The full structure of one isomer was established by X-ray diffraction analysis. The ring system was fragmented on heating in toluene (110°C, 22–48 hrs) or on irradiation (30–35°C, 254 nm, 24 hrs) with the release of the P[sbnd]O bridging unit as a metaphosphoramidate (RR′N[sbnd]PO.). In the photolytic metho...

ChemInform Abstract: An Investigation of the Retro Diels-Alder Reaction as a Method for the Generation of Diatomic Sulfur.

The cyclic disulfides 2,3-dithiabicyclo[2.2.2]oct-5-ene 5, 1,4-dihydro-2,3-benzodithiin 6 and hexa-hydro-5,8-epoxy-2,3-benzodithiin 7 have been prepared by oxidation of the corresponding dithiols. Each of these compounds has been subjected to vapour phase pyrolysis in order to determine whether a retro Diels–Alder reaction occurs, leading to the formation of diatomic sulfur (S2) and a diene. Compounds 5 and 7 both appeared to decompose in this way; in each case the expected diene was detected in the pyrolysate together with sulfur (S8). Attempts to intercept S2 and thus to obtain direct evidence for its formation were not successful. The benzodithiin 6 underwent an analogous loss of sulfur on vapour phase pyrolysis, but only as a minor reaction pathway, and this decomposition pathway was not detectable in solution pyrolyses. Solution pyrolysis of 6 in the presence of N-phenylmaleimide gave N-phenyl-2,3-naphthalimide 21 in low yield. cis-Cyclopentene-3,5-dithiol 9 has also been prepared but no evidence could be obtained for the formation of the disulfide 4 on oxidation. Reaction of the dithiol 9 with aldehydes and ketones in the presence of acids led to the formation of adducts (such as 12 and 13 from acetone) which were rapidly interconverted in acidic media.

Photochemistry of dicarbonyl-substituted benzenes: influence of steric and electronic factors in the cyclization and Diels-Alder trapping reactions of photoenols

We have examined the photochemistry of a broad set of diketones 1-6 containing o-methyl substituents. Whereas sterically-congested diketones 1 and 2 are found to undergo diphotocyclization to afford high yields of bis-benzocyclobutenols (BCBs), photolysis of 3, 4 and 6, which are devoid of steric congestion, is found to lead to an intractable material; in these cases, the initially formed photoenols appear to derive stabilization from the second electron withdrawing group (electronic effect) such that other competing reactions become promoted. Quite remarkably, it is these ketones that undergo very efficient tandem photoenolization-Diels- Alder cycloaddition reactions in the presence of an excellent dienophile such as N- phenylmaleimide to yield novel Diels-Alder cycloadducts in near quantitative yields. Photolysis of sterically-encumbered ketones 1, 2 and 5 in the presence of N-phenylmaleimide is found to result in the suppression of the formation of benzocyclobutenols with virtually insignificant formation of the product; the short-lived photoenols appear to revert rapidly to the precursor ketones. Thus, we have unraveled a subtle role of steric and electronic factors in the diphotocyclization and 2-fold tandem photoenolization-Diels-Alder cycloaddition reactions of diketones.

Diels-Alder Reaction and Double Phenylation in Reaction of Thiophenes with Diphenyliodonium Triflate

The reaction of 2,5-dimethylthiophene with diphenyliodonium triflate in the presence of N-phenylmaleimide and a catalytic amount of Cu(OAc) 2 gave 1:1 and 1:2 cycloadducts with N-phenylmaleimide. The similar reactions of 2,5-bis(trimethylsilyl)thiophene, 3-phenylthiophene, and thiophene afforded 2,5-diphenylthiophene, 2,3,5-triphenylthiophene, and 2,5-diphenylthiophene, respectively. The cycloadducts and 2,5-diphenylated thiophenes are considered to be formed via S-phenylation of thiophenes affording 1-phenylthiophenium triflates.

The crystal structure of a novel product from the acid-catalyzed condensation of 1-benzylindole with acetone

The acid-catalyzed condensation of 1-benzylindole with acetone in the presence of N-phenylmaleimide gave a tetrahydrocarbazole, (4,5,10,10b-tetrahydro-5-methyl-2-phenyl-10-(phenylmethyl)pyrrolo[3,4-a]carbazole-1,3[2H, 3aH]-dione (1), as the major product and a novel spiro compound, 1′,3,4,4′-tetrahydro-1′,1′,3,3-tetramethyl-4,4′-bis(phenylmethyl)-1,3′(2H, 2′H)-spiro[cyclopent[b]indole] (2), as the minor product. The structure of the spiro compound was determined by an X-ray crystallographic determination. The acid-catalyzed condensation of 1-benzylindole with acetone in the absence of N-phenylmaleimide gave a bisindole, (1,1′-bis(phenylmethyl)-3,3′-(1-methylethylidene)diindole (3), as the major product and the spiro-compound as the minor product.

Products derived from oxidations of 3,4‐dimethyl‐1‐phenylphosphole‐1‐oxide: A 3‐phenyl‐5,6‐dimethyl‐2,3‐oxaphosphabicyclo[2.2.2]octene‐3‐oxide derivative as a precursor of phenyl metaphosphonic anhydride

AbstractOxidation of 3,4‐dimethyl‐1‐phenylphosphole with peracids or peroxides gives a relatively stable P‐oxide, which can be used in Diels‐Alder reactions to give derivatives with the 7‐phosphanorbornene framework. Oxygen insertion into a C–P bond of this framework occurs smoothly with m‐ chloroperbenzoic acid (MCPBA) providing derivatives of the 2,3‐oxaphosphabicyclo [2.2.2] octene ring system. The phosphole can be converted to this system in a one‐pot synthesis by reaction with excess MCPBA in the presence of N‐phenylmaleimide as dienophile. The phosphole oxide undergoes mono‐epoxidation with MCPBA. Thermal or photochemical fragmentation of the 2,3‐oxaphosphabicyclo [2.2.2] ocetene is a useful source of the 3‐coordinate species Ph–PO2, a meta‐anhydride of phenylphosphonic acid. This species was trapped successfully with a variety of alcohols.

Radiation-induced crosslinking of polyvinylidene fluoride

The radiation-induced crosslinking of polyvinylidene fluoride (PVDF) was studied using N,N'-m-phenylenedimaleimide (PhDMI). It was shown that the addition of sensitizer results in a nearly two-fold decrease in the absorbed dose required for crosslinking. The main radiation-chemical parameters of the crosslinking process were determined. The mechanism of PVDF crosslinking in the presence of N-phenylmaleimide (PhMI), PhDMI and its saturated analogue, N,N'-m-phenylenedisuccinimide (PhDSI) was studied by ESR spectroscopy. The results indicate the probability of forming a crosslinked structure, which is really a system of interpenetrating networks.

XY–ZH systems as potential 1,3-dipoles. Part 10. The decarboxylative route to azomethine ylides. Background and relevance to pyridoxal decarboxylases

The reaction of primary and α,α-disubstituted α-amino acids with pyridoxal in the presence of N-phenylmaleimide in various solvents at temperatures up to 120 °C gives rise to two series of cycloadducts. One series arises from azomethine ylides formed by decarboxylation of the intermediate pyridoxal imines whilst the other series arises via azomethine ylides derived by 1,2-prototropy in the same pyridoxal imines. The relevance of the decarboxylative route to azomethine ylides to the Strecker degradation and to pyridoxal-mediated decarboxylase enzymes is discussed.

O-Quinonoid compounds. Part 18. Stabilised 2,3-naphthoquinodimethanes via transient 1,3-diphenylbenz[f]inden-2-one

1,3-Diphenylbenz[f]inden-2-one (8) can be reversibly generated by thermolysis of its formal (π4s+π4s)-dimer (11) which is itself available in 5 steps from benz[f]indan-1,3-dione; (8) adds stereospecifically to cis- and trans-but-2-ene. Photodecarbonylation of the adducts (23), (21), and (22) derived by trapping (8) with norbornadiene, trimethylmaleimide, and the dienophile (24) gives the sterically stabilised 2,3-naphthoquinodimethanes (29), (25), and (26) respectively. These are long-lived in fluid solution at 20 °C and were characterised by u.v.–visible spectroscopy and as their adducts with 4-phenyltriazoline-3,5-dione (PTD). 1,3,4,9-Tetraphenylbenz[f]inden-2-one (37) generated by reaction of its dibromide (10; X = O, Y = Br) with sodium iodide forms the formal (π6s)+π6s)-dimer (35). Dissociation of (35) in the presence of N-phenylmaleimide gives the adduct (15).

Preparation and thermal fragmentation of imidazolidines derived from aryl imines

Aryl imines of diethyl aminomalonate undergo facile dimerisation to imidazolidines. Heating the imidazolidines at 110° in the presence of N-phenyl maleimide or diethyl azodicarboxylate gives pyrrolidines and triazolidines respectively via a retro 1,3-dipolar cycloaddition.

Radiation crosslinking of ethylene-prophylene rubber in the presence of N-phenylmaleimide as sensitizer

Radiation crosslinking of ethylene-prophylene rubber in the presence of N-phenylmaleimide as sensitizer

Studies on the reaction of benzoyl peroxide with NN-disubstituted aromatic amines and other related compounds. Part IV. A novel formation of 1,2,3,4-tetrahydroquinoline derivatives

The reaction of benzoyl peroxide with NN-dimethylaniline in cumene or chloroform at ca. 0° in the presence of N-phenylmaleimide gives 1,2,3,4-tetrahydro-1-methylquinoline-N-phenyl-3,4-dicarboximide, formed via the N-methylanilinomethyl radical. This reaction provides a convenient way of differentiating between the PhNMe·ĊH2 radical and the (PhNMe:CH2)+ cation as intermediates. The latter does not react with N-phenylmaleimide, although it reacts with ethyl vinyl ether to give 4-ethoxy-1,2,3,4-tetrahydro-1-methylquinoline. The formation of quinoline derivatives by use of benzoyl peroxide succeeds also with N-methylmaleimide (instead of the N-phenyl compound) and with a number of other aromatic tertiary amines, including N-phenyl- and N-p-tolyl-pyrrolidine; yields of products obtained are of preparative value. Reduction of the products gives 2,3,3a,4,5,9b-hexahydro-5-methyl-2-phenyl-1H-pyrrolo[3,4-c]quinoline, 2,3,3a,3b,4,5,6,11b-octahydro-2-phenyl-1H-dipyrrolo[1,2a,3,4-c]quinoline, and derivatives thereof.