Photochemical reactions of 7-aminocoumarins. 2. [2 + 2]-cycloadducts with styrene

The photocycloaddition of styrene to 4-methyl-7-aminocoumarin, 4-methyl-7-diethylaminocoumarin, 7-(N-morpholino) coumarin, 3-ethoxycarbonylmethyl-4-methyl-7-diethylaminocoumarin, and coumarin-102 (2,3,6,7-tetrahydro-9-methyl-1H, 5H,11H-[l]-benzopyrano[6,7,8-ij] quinolizin-11-one) was investigated. Adducts of regio- and stereospecific [2 + 2]-cycloaddition to the 3–4 bond were isolated. It was established by means of x-ray diffraction analysis that the phenyl group in the cycloadducts occupies the 1-endo position. The participation of the singlet excited states of the 7-aminocoumarin molecules in [2 + 2]-cycloaddition was demonstrated.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1176–1184, September, 1988.     

Photochemical reaction of 7-aminocoumarins. 9. [2+2]-Cycloadducts with trans,trans-1,4-diphenyl-1,3-butadiene

The photoreactions of 7-diethylaminocoumarin, 4-methyl-7-diethylaminocoumarin, 4-trifluoromethyl-7-diethylaminocoumarin, and 4-N-morpholino-7-diethylaminocoumarin with trans,trans-1,4-diphenyl-1,3-butadiene, which lead to the formation of [2+2]-cycloaddition products, were studied. It was established that photocycloaddition proceeds with the formation of adducts that have a 1-endo-styryl substituent and a 2-exo-phenyl group. The effect of the substituent in the 4-position of the 7-aminocoumarin molecule on the effectiveness of cycloaddition is discussed.See [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1319–1325, October, 1990.     

Photochemical reactions of 7-aminocoumarins 1. [2 + 2]-cycloadducts with vinyl butyl ether and acrylonitrile

Adducts of [2 + 2]-cycloaddition to the 3–4 bond were isolated in the photochemical cycloaddition of vinyl butyl ether and acrylonitrile to 4-methyl-7-diethylaminocoumarin. The stereochemical structures of the compounds obtained as isomers of the head-to-tail type with an endo or exo orientation of the substituents were established by means of PMR spectroscopy. As a result of an evaluation of the effect of sensitizers and one-electron oxidizing and reducing agents it was found that the investigated reactions proceed through the singlet excited states of 7-aminocoumarins. It is assumed that the regiospecificity of the [2 + 2]-cycloaddition is determined by the C(₃) reaction center of the coumarin fragment.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1169–1175, September, 1988.     

Photochemical reactions of 7-aminocoumarins.

A number of 3-aryl-4-methyl-7-diethylaminocoumarins were obtained as a result of the photolysis of 3-iodo-4-methyl-7-diethylaminocoumarin in the presence of benzene, chlorobenzene, fluorobenzene, benzonitrile, toluene, and diphenyl ether. On the basis of an analysis of the PMR spectra it was established that photosubstitution leads to o- and p-isomeric products. The mechanism of the reaction was studied.See [1] for Communication 7.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1172–1176, September, 1990.     

Photochemical reactions of 7-aminocoumarins

The photochemical reactions of 4-methyl-7-diethylaminocoumarin with the dimethyl ester of acetylenedicarboxylic acid, diethyl ester of maleic acid, and N-phenylmaleimide in the presence of oxygen and acetophenone give products of the heterocyclization at C(₆) and C(₈) of coumarin fragment with participation of the diethylamino group. The stereochemical structure of the compounds synthesized was demonstrated using PMR spectroscopy. A mechanism was proposed for this reaction involving the formation of an -amino radical and its addition to the acetylene or olefin, accompanied by attack on the aromatic ring with subsequent aromatization.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 30–36, January, 1989.     

Photochemical reactions of 7-aminocoumarins. 6. Reaction of 7-dialkylaminocoumarins with halo derivatives

3-Substituted 7-dialkylaminocoumarins were synthesized as a result of the photoreaction of 7-diethylaminocoumarin, 4-trifluoromethyl-7-diethylaminocoumarin, 4-chloro-7-diethylaminocoumarin, 4-(N-morpholino)-7-diethylaminocoumarin, and coumarin-102 (2,3,6,7-tetrahydro-9-methyl-1H,5H,11H-[1]-benzopyrano[6,7,8-ij]quinolizin-11-one) with iodobenzene, 3,4-dimethoxyiodobenzene, isopropyl iodide, and ethyl -bromoacetate. It was established that electron-acceptor and electron-donor substituents in the 4 position accelerate photosubstitution. The spectral-luminescence characteristics of the compounds obtained were investigated.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 1028–1032, August, 1990.     

Photochemical reactions of 7-aminocoumarins. 7. Reaction of 3-iodo-4-methyl-7-diethylcoumarin with olefins

A number of new 7-aminocoumarins having an unsaturated substituent in the 3 position were obtained as a result of photolysis of 3-iodo-4-methyl-7-diethylaminocoumarin with olefins, viz., styrene, acrylonitrile, methyl acrylate, methyl methacrylate, 4-vinylpyridine, 2-ethoxypropene, indent, ethyl -anilinocrotonate, and 2,5-norbornadiene, as well as with phenylacetylene. Regiospecificity and stereospecificity of the investigated photoreactions were established. The spectral-luminescence characteristics of the synthesized compounds are presented.For Communication 6, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1033–1041, August, 1990.     

Photochemical reactions of 7-aminocoumarins. 10. Reaction of 3-iodo-4-methyl-7-diethylaminocoumarin with heteroaromatic compounds

Photolysis of 3-iodo-4-methyl-7-diethylaminocoumarin in the presence of N-methylpyrrole, furan, thiophene, selenophene, pyridine, indole, imidazole, and benzimidazole results in the formation of a series of 3-hetaryl-7-aminocoumarins. The spectral luminescence characteristics of these newly synthesized compounds have been investigated.For communication 9, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1469–1473, November, 1990.     

Photochemical reactions of 7-aminocoumarins. 4. Reaction of 4-methyl-7-diethylaminocoumarin with compounds tending to photolytic dissociation

The photochemical reactions of 4-methyl-7-diethylaminocoumarin with a series of alkyl halides including isopropyl iodide, allyl iodide, bromoacetone -bromoethyl acetate, phenacyl bromide, p-bromophenacyl bromide, and chloroacetonitrile, and aryl iodides including iodobenzene, 2-nitroiodobenzene, 3,4-dimethoxyiodobenzene, and 3-iodo-4-methyl-7-diethylaminocoumarin proceed by a radical addition mechanism to give 3-substituted aminocoumarins. A series of 3-substituted 7-aminocoumarins was also obtained as a result of the photochemical reactions of 4-methyl-7-diethylaminocoumarin, with other reagents, having photolabile chemical bonds such as dioxanyl peroxide, phenyl iodosodiacetate, and nitromethane. The luminescence characteristics of the compounds synthesized were studied.For Communication 3, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 460–469, April, 1989.     

Rhodium N-heterocyclic carbene-catalyzed [4 + 2] and [5 + 2] cycloaddition reactions

[reactions: see text] A rhodium complex of N-heterocyclic carbene (NHC) has been developed for intra- and intermolecular [4 + 2] and intramolecular [5 + 2] cycloaddition reactions. This is the first use of a transition-metal NHC complex in a Diels-Alder-type reaction. For the intramolecular [4 + 2] cycloaddition reactions, all the dienynes studied were converted to their corresponding cycloadducts in 91-99% yields within 10 min. Moreover, up to 1900 turnovers have been obtained for the intramolecular [4 + 2] cycloaddition at 15-20 degrees C. For the intermolecular [4 + 2] cycloadditions, high yields (71-99%) of the corresponding cycloaddition products were obtained. The reaction time and yield were highly dependent upon the diene and the dienophile. For the intramolecular [5 + 2] cycloaddition reactions, all the alkyne vinylcyclopropanes studied were converted to their corresponding cycloadducts in 91-98% yields within 10 min. However, the catalytic system was not effective for an intermolecular [5 + 2] cycloaddition reaction.     

[7+2]- and [11+2]-cycloaddition reactions of diazo-azoles with isocyanates to azolo[5,1-d] [1,2,3,5] tetrazine-4-ones

Diazo-azoles react as 1,7- or 1,11-dipoles with isocyanates to form the hitherto unknown pyrazolo[5,1-d] [1,2,3,5]tetrazine-4-ones, [1,2,3,5]tetrazino[5,4-b]indazole-4-ones and [1,2,3]triazolo[5,1-d][1,2,3,5]tetrazine-4-ones in a [7+2]- or [11+2]-cycloaddition reaction.     

Catalytic enantioselective [2 + 4] and [2 + 2] cycloaddition reactions with propiolamides

We report here the catalytic and highly enantioselective [2 + 4] and [2 + 2] cycloaddition reactions of electron-rich dienes or silyl enol ethers with electron-deficient propiolamide derivatives induced by copper(II).3-(2-naphthyl)-L-alanine amide complex.     

Reactions with diazoazoles. Part IV. . [7 + 2]- and [11 + 2]-cyclocondensation reactions of diazoazoles with acyltriphenylphosphonium methylides to azolo[5,1-c][1,2,4]triazines

Acyltriphenylphosphoniummethylides react with diazoazoles in a [2 + 7]- or [2 + 11]-cycloaddition reaction followed by elimination of triphenylphosphane oxide to yield azolo[5,1-c][1,2,4]triazines.     

[2+2]- AND [4+2] cycloaddition reactions of 1,3-diazabutadienes with diphenylketene

1,3-Diazabutadienes react with diphenylketene in [2+2] - and [4+2] cycloaddition reactions, depending on the substitution pattern. Spectroscopic data (IR, ¹H- and ¹³C-NMR) and results of quantummechanical model calculations (ab initio 3-21G) are presented.     

Photochemical [2 + 2] cycloaddition of acetylene to chiral 2(5H)-furanones

The [2 + 2] photocycloaddition of acetylene to chiral 2(5H)-furanones was investigated. The influence on the chemical yield and facial diastereoselectivity of the substituent at the stereogenic center and also the effect of a 4-methyl group were evaluated. A mechanistic proposal based on a simple theoretical conformational analysis is presented. Using a C(2)-symmetric bis(lactone) as the substrate, a diastereomeric excess higher than 98% was found.     

Catalytic [2+2] and [3+2] cycloaddition reactions of allenoates with cyclic ketimines

Cyclic ketimines as electrophiles for [2+2] and [3+2] cycloaddition reactions of allenoates have been developed, affording functionalized sultam-fused azetidines and dihydropyrroles, respectively, in good yields with high regioselectivities.     

4-R-7-Nitrobenzofurazans in [3+2] cycloaddition reactions with N-methylazomethine ylide

A number of new tetrahydroisoindole derivatives fused with the furazan ring were synthesized based on the 1,3-dipolar cycloaddition of N-methylazomethine ylide with substituted 4-nitrobenzofurazans. Substituents in the benzene ring were found to affect the cycloaddition process.     

Photochemical [3 + 2] cycloaddition of 2-cyanochromone to olefins

Irradiation of 2-cyanochromone in the presence of olefins gave rise to [3 + 2] cycloadducts together with the formation of normal [2 + 2] cycloadducts with the product ratio being temperature-dependent. The mechanism involving a vinyl nitrene intermediate was proposed.     

Solid-State Photochemical [2+2] Cycloaddition Reaction of MnII Complexes

Three Mn^II complexes have been synthesized under similar experimental conditions. Of these [Mn₂(benzoate)₄(L)₂] (where L=4-styrylpyridine or 4spy, 1 and 2-fluoro-4′-styrylpyridine or 2F-4spy, 3 ) are paddlewheel complexes, but crystallized in different space groups. Whereas [Mn₂(benzoate)₄(3F-4spy)₄] (3F-4spy=3-fluoro-4′-styrylpyridine), 4 is a dinuclear complex having different stoichiometry from 1 and 3 with two pairs of 3F-4spy ligands aligned in face-to-face manner. An irreversible phase transition occurs from the space group P2₁/c to C2/c when 1 was heated up to 125 °C to 2 in a single-crystal-to-single-crystal fashion or when ground 1 to powder. 2 is isomorphous and isostructural to 3 . Complimentary π–π interactions in head-to-tail alignment of the styrylpyridine ligands furnishes 1D aggregates in 1 – 3 which are congenial to undergo [2+2] cycloaddition reaction under UV light. Whereas, face-to-face alignment of the 4spy pairs in 4 is expected to provide a head-to-head photoproduct. All the Mn^II complexes are indeed found to be photoreactive. To our surprise, contrary to their Zn^II analogues, 2 and 3 were not found to be photosalient. The percentage volume expansion during the photoreaction as determined from the density measurements, was found to be too low (3.2 and 4.6 % respectively for 2 and 3 ) to have this behavior.