Reaction of trichloroacetyl isocyanate with vinyl sulfides

Conclusions Trichloroacetyl isocyanate reacts with the n-butyl, isoamyl, and phenyl vinyl sulfides on the type of 1, 4-cycloaddition with the formation of 3, 1-oxazin-6-one derivatives.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2324–2325, October, 1972.     

Synthesis of 1-trichloeoacetyl-2-teichloeomethyl-1,3-diaza-2-cyclobuten-4-one

Conclusions Trichloroacetyl isocyanate reacts with trichloroacetonitrile on the type of 22-cycloaddition with the formation of 1-trichloroacetyl-2-trichloromethyl-1,3-diaza-2-cyclobuten-4-one.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimichesckaya, No. 10, pp. 2325–2326, October, 1972.     

Reaction of trifluoroacetyl isocyanate with Schiff bases

Conclusions Trifluoroacetyl isocyanate reacts with Schiff bases on the type of 2 + 4-cycloaddition to give substituted 4-oxo-1, 3,5-oxadiazines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.1, pp.202–204, January, 1976.     

Heterodiene syntheses—X : Reaction of arylidene-pyrazolones and -isoxazolones with dihydropyran: Nature of the transition state

Dihydropyran reacts easily with the α, β-unsaturated carbonyl system of heterocyclic rings (pyrazoles or isoxazoles) in accordance with a 1,4-cycloaddition.     

Cycloaddition von Heterocumulenen an CN-Bindungssysteme. 1. Mitteilung. Perhydro-s-triazindione und Perhydro-s-triazinyl-harnstoffe aus N,N,N′-trisubstituieten Formamidinen und Isocyanaten

The addition of methyl isocyanate to N,N-dimethyl-N′-arylformamidines 4d – 4r leads to the perhydro-s-triazine-diones 5d – 5o and to the s-triazinylureas 10a – 10k . The mechanism of formation is discussed. The addition of the arylisocyanates 18a – 18p to the N,N,N′-trialkylformamidines 9 and 27a – 27i furnishes the expected 1,4-cycloaddition products 26 and 27 in good yields. The N,N-di-isopropyl-N′-alkylformamidines 27j – 271 , however, do not undergo 1,4-dipolar cycloadditions and react with the arylisocyanate 18b to yield the alkyl isocyanates 31a – 31c and N,N-diisopropyl-N′-(p-chlorphenyl)-formamidine 32 exclusively.     

Reaction of benzoyl and trichloroacetyl isocyanates with quinoline

Conclusions Trichoroacetyl isocyanate under the influence of quinoline forms ditrichloroacetylcarbodiimide, which adds to the C=N bond of quinoline on the type of a 2+4-cycloaddition. Benzoyl isocyanate under the influence of quinoline forms the dimer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.2, pp.456–458, February, 1973.     

Heterodiene syntheses—XIV: The reaction of 3-oxindolideneacetophenones with ethyl vinylether

Ethyl vinylether reacts with 3-oxindolideneacetophenones. In addition to some 2,3-dihydropyran[2,3-b]indoles, obtained by 1,4-cycloaddition, previously unknown 3-(3-oxindolyl)dihydrofurans whose origin may involve a dipolar intermediate were isolated. Rationalization of the mechanism is proposed and the approach in terms of frontier orbitals is discussed.     

Action of Lawesson's reagent on substituted 2‐amino‐1,4‐naphthoquinones: Novel synthesis of benzodiphenoquinone‐bis‐1,3,2‐thiazaphospholine‐2‐sulfide derivatives

1,3,2,4‐Dithiadiphosphetane‐2,4‐disulfide 1 reacts with substituted 2‐amino‐1,4‐naphthoquinons 2a–d to give 4,5,4′,5′‐benzodiphenoquinone‐bis‐1,3,2‐thiazaphospholine‐2‐sulfide derivatives of type 3. Compatible analytical and spectroscopic results were obtained for all the new compounds. A mechanism is proposed to explain the formation of compounds 3. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 488–491, 1999     

1,1-Cycloaddition of oxalyl dichloride with dialkenylmetal compounds: formation of cyclopentadienone derivatives by the reaction of 1,4,-dilithio-1,3-dienes or zirconacyclopentadienes with oxalyl chloride in the presence of CuCl

1,4-Dilithio-1,3-dienes or zirconacyclopentadienes reacted with oxalyl chloride in the presence of CuCl in a 1,1-cycloaddition manner to give cyclopentadienone derivatives in high yields along with the elimination of CO.     

Intramolecular 1,3-cycloadditions of nitrile ylides bearing an acetylenic function

Treatment of amides 1a,b with thionyl chloride followed by reaction with triethylamine gave 1,4-dihydro[1]benzopyrano[4,3-b]pyrrole derivatives ( 4a,b ) arising from intramolecular 1,3-cycloaddition of intermediate nitrile ylides ( 3a,b ).     

A new reaction of vicinal sulfonyliminocarboxylates with phosphites

The reaction of alkyl trifluoro(organylsulfonylimino)propionates with phosphites occurs with NC transfer of the RSO₂ group and leads to sulfonyl-substituted trifluoroalanine derivatives. The novel rearrangement is interpreted as cheletropic 1,4-cycloaddition of the phosphite and subsequent 1,2-shift of the sulfonyl group in the intermediate cyclic phosphorane.     

Access to thiomorpholin-3-one derivatives: [3 + 3]-cycloadditions of α-chlorohydroxamates and 1,4-dithiane-2,5-diol

A protocol of [3 + 3]-cycloaddition was proposed for the synthesis of 2H-1,4-thiazin-3(4H)-ones and thiomorpholine-3,5-diones from α-chlorohydroxamates and 1,4-dithiane-2,5-diol. This direct and practical method provides a novel and rapid approach for the synthesis of thiomorpholin-3-one derivatives under mild condition with moderate to good yield and wide functional group tolerance.     

Product structure in the reaction of dimethyl acetylenedicarboxylate with 2-furyl-1,2,3,4-tetrahydroquinolines

Dimethyl acetylenedicarboxylate reacts with 4-substituted and 3,4-fused 2-furyl-1,2,3,4-tetrahydroquinoline derivatives at the furan fragment according to the [4 + 2]-cycloaddition pattern. The reaction is not stereoselective, and it yields two diastereoisomeric 7-oxabicyclo[2.2.1]hepta-2,5-dienes whose structure was determined by X-ray analysis and NMR spectroscopy.     

Synthesis of 2-ethoxyprop-2-enal dimethylhydrazone and its Diels-Alder reactions

Conditions were found for the preparation of 2-ethoxyprop-2-enal dimethylhydrazone by reaction of 2-ethoxypropenal with N,N-dimethylhydrazine. 2-Ethoxyprop-2-enal dimethylhydrazone reacted with methyl vinyl ketone and methyl acrylate according to the [4 + 2]-cycloaddition pattern with regioselective formation of substituted tetrahydropyridines. The major product in the reaction of 2-ethoxyprop-2-enal dimethylhydrazone with 1,4-benzoquinone was 5-hydroxy-1-benzofuran-2-carbaldehyde dimethylhydrazone formed as a result of [3 + 2]-cycloaddition; a small amount of the corresponding [4 + 2]-cycloaddition product was also obtained. Some spontaneous transformations of the primary cycloaddition products were revealed.     

Synthetic transformations of higher terpenoids: XVII. Intramolecular cyclization of N-furfuryl amides of the labdane series

16-(Benzylaminomethyl)lambertianic acid methyl ester reacts with 2-methylprop-2-enoyl chloride to give unsaturated amide which readily undergoes intramolecular [4 + 2]-cycloaddition with formation of terpenoid derivatives of 10-oxa-3-azatricyclo[5.2.1.0^1,5]decenone. Acetylation of lambertianic acid methyl ester with acetic anhydride occurs preferentially at the 2-position of the furan ring and is accompanied by migration of the exocyclic double bond. Reductive amination of 16-acetyl-15,16-epoxylabda-8(9),13,14-triene and subsequent reaction of the resulting amine with 2-methylprop-2-enoyl chloride give intramolecular cyclization products in high yield without isolation of intermediate furfurylacryloyl derivative. Reactions of methyl 16-(benzylaminomethyl)-15,16-epoxylabda-8(9),13,14- and -8(17),13,14-trien-18-oates with maleic anhydride lead to the formation of the corresponding 10-oxa-3-azatricyclo[5.2.1.0^1,5]dec-8-ene-6-carboxylic acid derivatives as mixtures of diastereoisomers.     

Some reactions of 3,6-disubstituted-s-tetrazines; A new synthesis of the 1,2,4-triazine ring system

The synthesis of variously substituted pyridazines by 1,4-cycloaddition of cyclic enol ethers, esters, and some electron-rich acetylenes is described. Extension of the scheme to include some imino-ethers as dienophiles resulted in the synthesis of 1,2,4-triazine derivatives.     

Theoretical study of the reaction of vitamin B6 with 1O2

Singlet oxygen is known to cause oxidative stress in cells, leading to severe damage (e.g., lipid peroxidation, membrane degradation, mutagenic alterations to DNA, protein misfunctionality). Recently, pyridoxine has been discovered to be capable of quenching singlet oxygen, however, the mechanism of this reaction remains essentially unknown. In this work, we have investigated four sets of reactions: 1) 1,3-addition to a double bond connected to a hydrogen-carrying group, resulting in the formation of allylic hydroperoxides; 2) [pi2+pi2] 1,2-cycloaddition to an isolated double bond, resulting in the formation of 1,2-peroxides; 3) 1,4-cycloaddition to a system containing at least two conjugated double bonds, resulting in the formation of the so-called 1,4-peroxides; 4) 1,4-addition to phenols and naphthols with the formation of hydroperoxide ketones. Thermodynamically, reaction 4 and the 6(9), 3(8), and 5(8) cases of reaction 1 are the most exergonic ones, with energies ranging from -16 to -18 kcal mol(-1). Furthermore, reaction 4 shows the lowest barrier through the reaction path, and is predicted to be the preferred mechanism for the pyridoxine + singlet-oxygen reaction, which is in agreement with previous experimental results.     

Chemoselectivity in the Reaction of 2‐Diazo‐3‐oxo‐3‐phenylpropanal with Aldehydes and Ketones

The chemoselectivity in the reaction of 2‐diazo‐3‐oxo‐3‐phenylpropanal ( 1 ) with aldehydes and ketones in the presence of Et₃N was investigated. The results indicate that 1 reacts with aromatic aldehydes with weak electron‐donating substituents and cyclic ketones under formation of 6‐phenyl‐4H‐1,3‐dioxin‐4‐one derivatives. However, it reacts with aromatic aldehydes with electron‐withdrawing substituents to yield 1,3‐diaryl‐3‐hydroxypropan‐1‐ones, accompanied by chalcone derivatives in some cases. It did not react with linear ketones, aliphatic aldehydes, and aromatic aldehydes with strong electron‐donating substituents. A mechanism for the formation of 1,3‐diaryl‐3‐hydroxypropan‐1‐ones and chalcone derivatives is proposed. We also tried to react 1 with other unsaturated compounds, including various olefins and nitriles, and cumulated unsaturated compounds, such as N,N′‐dialkylcarbodiimines, phenyl isocyanate, isothiocyanate, and CS₂. Only with N,N′‐dialkylcarbodiimines, the expected cycloaddition took place.     

Straightforward carbamoylation of nucleophilic compounds employing organic azides, phosphines, and aqueous trialkylammonium hydrogen carbonate

In the presence of aqueous trialkylammonium hydrogen carbonate, the Staudinger reaction leads to the intermediate formation of the corresponding isocyanate, which, in turn, reacts further with a nucleophilic reagent also present in the mixture and results in carbamoylation with good yield. On the basis of this reaction a practical carbamoylation procedure was devised and a comparative study on suitability of different solvents and phosphorus (III) derivatives for carbamoylation reaction was conducted. The versatility of the method was demonstrated by examples with different classes of nucleophilic compounds that included the aminomethyl resin and natural compounds that display poor solubility in organic solvents.     

Kinetics and mechanism of reaction of p-methoxystyrene and tetracyanoethylene. II. Effect of pressure

The reaction of p-methoxystyrene and TCNE is studied in 50% CHCl₃–50% CCl₄ (v/v) at 25°C at high pressures up to 1000 bar by following the disappearance of the absorbance at 600 nm due to the EDA complex. By using the mixed solvent, equations required for the high-pressure kinetics are simplified. The volume of activation is ?42 to ?46 cm³/mol for the 1,4-cycloaddition and ?55 cm³/mol for the 1,2-cycloaddition. The activation volume for the 1,4-cycloreversion is assumed to be ?8 to ?12 cm³/mol based on a previous study on a similar system. The rate of the cycloreversion process is affected by solvent polarity. The rate of the 1,2-cycloaddition is influenced by solvent more significantly than that of the 1,4-cycloaddition. It is concluded that the transition state is polar in both cycloadditions and that its zwitterionic character is much stronger in the 1,2-cycloaddition.