Huisgen reaction of nitrile oxides and nitrile imines leading to isoxazoline and pyrazole-4,6-diones

Huisgen reaction of nitrile oxides and nitrile imines generated in situ in the presence of N-benzylmaleimide afforded regiospecifically the corresponding cis-3-aryl-5-benzyl-3a,4,6,6atetrahydro-4H, 6H-pyrrolo[3,4-d]isoxazoline-4,6-diones and cis-3-aryl-5-benzyl-1-(2′,4′-dibromophenyl)-3a, 4,6,6a-tetrahydro-1H,5H-pyrrolo[3,4-c]pyrazole-4,6-diones in good yield. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 935–939, June, 2006.     

Reaction of 2-azabicyclo[2.2.1]heptenes with nitrile oxides

The reaction of 2-azanorbornene derivatives with nitrile oxides (generated in situ by dehydrohalogenation of N-hydroxyimoyl halides) affords two regioisomers with the exo-arrangement of the isoxazoline ring.     

Regioselectivity in the 1,3-dipolar cycloaddition of nitrile oxides to 3,3-methylene-5,5-dimethyl-2-pyrrolidinone

Summary Nitrile oxides add regioselectively to the carbon-carbon double bond of 3,3-methylene-5,5-dimethyl-2-pyrrolidinone (1), giving exclusively spiro-isoxazolines: 3-aryl-6-oxo-8,8-dimethyl-1-oxa-2,7-diazaspiro[4.4]non-2-enes3 a–l. The regiochemistry of the 1,3-dipolar cycloaddition to 1 seems to be controlled by the steric effect of the methyl groups at the ring junction and by frontier orbital interactions.Part XXV in the series 1,3-Dipolar Cycloaddition on Heterocycles. Part XXIV Ref. [10]     

Syntheses with nitrile oxides. 2. Reaction of aromatic nitrile oxides with bis(trimethylsilylcarbodiimide)

The reaction of aromatic nitrile oxides with bis(trimethylsilylcarbodiimide) gives 5-amino-3-aryl-1,2,4-oxadiazoles.For previous communication, see [1].N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117334 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2430–2432, October, 1992.     

锗苯与腈氧化物1,3偶极环加成反应理论研究

采用密度泛函理论(DFT)方法在B3LYP/6-311G**水平研究了锗苯与腈氧化物的1,3偶极环加成反应的微观机理、势能剖面,考察取代基和四氢呋喃溶剂对反应势能剖面的影响.计算结果表明,所研究反应均以协同但非同步的方式进行,且总是Ge—O键先于C—C键形成.锗苯分子中Ge原子上的给电子和吸电子取代基均有利于反应的进行,而腈氧化物C原子上的2,4,6-三甲苯基取代基在热力学上对反应很不利.四氢呋喃溶剂对所研究反应的势能剖面影响不大.     

1,3-偶极环加成合成新型3a,6a-二氢-4,6-二氧代吡咯啉并[3,4-d]吡唑类衍生物

α-氯代-4-氧代-4H-1-苯并吡喃-3-甲醛芳腙与N-取代苯基-马来酰亚胺在三乙胺作用下通过1,3-偶极环加成合成了一系列含3-(4-氧代-4H-1-苯并吡喃-3-基)-3a,6a-二氢-4,6-二氧代吡咯啉并[3,4-d]吡唑类衍生物. 化合物结构经元素分析, IR, ¹H NMR及MS确证.     

4-Hydroxyiminonitromethyl-2,2,5,5-tetramethyl-3-imidazolme-1-oxyl as a precursor of spin-labeled nitrile oxide

Paramagnetic nitrile oxide, a derivative of 3-imidazoline-1-oxyl, has been generated by thermolysis of geminal nitrooxime. This compound readily undergoes cycloaddition with alkenes with both activated and nonactivated C=C bonds. The paramagnetic nitrile oxide may be used for introducing a nitroxyl into molecules with multiple carbon-carbon bonds.For the previous communication, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 289–291, February, 1994.     

手性5-l-(艹孟)氧基丁内酯并[3,4-d]-3-取代基-异(口恶)唑啉类化合物的合成

研究了手性元5-(R)-(l-(艹孟)氧基)-2(5H)-呋喃酮与取代苯甲醛肟以次氯酸钙作为氧化剂进行的区域选择性原位1,3-偶极环加成反应,同步生成两个新的手性中心,得到了一系列光学纯丁内酯并[3,4-d]-3-取代基-异(口恶)唑啉类化合物;应用波谱学手段及X射线单晶衍射法确证了产物的绝对构型,并对产物的核磁共振氢谱规律性加以总结.     

Asymmetric 1,3-dipolar cycloaddition of nitrile oxides to chiral acryloyl esters bearing glucofuranose as auxiliary

Asymmetric 1,3-dipolar cydoaddition of nitrite oxides to an acryloyl ester (1) derived from 1,2:5,6-di-O-isopropylidene glucose (6) was studied. Solvent and temperature effect was discussed. The single diastereoisomer was isolated with high diastereoselective excess.     

N-N bond-forming cyclization for the one-pot synthesis of N-aryl[3,4-d]pyrazolopyrimidines

An efficient one-pot synthesis of N-aryl[3,4-d]pyrazolopyrimidines in good yield and under mild reaction conditions is described. By exploiting electron-deficient hydroxylamines, the substituted oxime products were formed with very high E-diastereoselectivity. The key step utilizes a cyclization reaction upon an oxime derived from hydroxylamine-O-sulfonic acid to form the N-N bond of the product.     

Catalyst free synthesis of fused pyrido[2,3-d]pyrimidines and pyrazolo[3,4-b]pyridines in water

A one-pot,three-component condensation reaction of an aldehyde,benzoyl acetonitrile(3-oxo-3-phenylpropane nitrile) and 6- amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione or 3-methyl-1-phenyl-1H-pyrazol-5-amine in water to give fused pyrido[2,3- d]pyrimidines and pyrazolo[3,4-b]pyridines in high yields without any catalyst,is described.     

A DFT study for the regioselective 1,3-dipolar cycloadditions of nitrile N-oxides toward alkynylboronates

The mechanism for the 1,3-dipolar cycloaddition of benzonitrile oxide toward ethynyl and propynylboronate has been studied by using density functional theory (DFT) at B3LYP/6-31G* level. These cycloadditions are concerted [3+2] processes. The presence of the two oxygens on the boronic ester precludes the participation of the boron atom on [3+3] processes. The two regioisomeric channels associated to the formation of the isoxazoles bearing the boronic ester unit on the 4- or 5-positions have been characterized. The B3LYP/6-31G* activation parameters are in acceptable agreement with the experiments, allowing to explain the factors controlling these regioselective cycloadditions.     

A stereoselective synthesis of spiro-dioxolanes via the multicomponent reaction of dicarbomethoxycarbene, aldehydes and 1,2- or 1,4-diones

The three component reaction of acyclic carbonyl ylides generated from dicarbomethoxycarbene and aldehydes with 1,2- and 1,4-diones is described. The reaction afforded the corresponding spiro-dioxolanes in good yields.     

Efficient synthesis of 1,2,4-oxadiazine-5-ones via [3+3] cycloaddition of in situ generated aza-oxyallylic cations with nitrile oxides

1,2,4-Oxadiazin-5-ones were prepared via [3+3] cycloaddition of in situ generated aza-oxyallylic cations with nitrile oxides in good yields and excellent functional group compatibility. This efficient transformation is metal-free and is promoted by an inorganic base Cs₂CO₃. In addition, this reaction features simple-operation, mild conditions, and high regioselectivity.     

Regioselectivity of cycloadditions of nitrile oxides and nitrones to 4-methylene-tetrahydrothiopyrane

Summary The cycloaddition of nitrile oxides and nitrones to 4-methylene-tetrahydrothiopyrane proceeds regioselectively under the formation of spiro-substituted isoxazole derivatives4 and9. Semiempirical calculations (AM1) were used to analyze the electronic structure of reactants, energies of products, and activation barriers leading to these products in order to rationalize this exclusive regioselectivity. It was shown that the main factor responsible for the high stereoselectivity of this reaction is not frontier orbital control, but mainly electrostatic and steric interactions. The spiro compounds4 were cleaved by hydrogenolysis to -amino-alcohols11, which were recyclized to spiro-oxazines12 and13.4 and9 as well as12 and13 are derivatives of novel heterocylic systems.

---

Regioselektive Cycloadditionen von Nitriloxiden und Nitronen an 4-Methylen-tetrahydrothiopyran

Zusammenfassung Die Cycloaddition von Nitrilen und Nitriloxiden an 4-Methylen-tetrahydrothiopyran zeigt einen regioselektiven Verlauf unter Bildung der spiro-substituierten Isoxazolderivate4 und9. Die elektronischen Strukturen von Reaktanden, Energien von möglichen Reaktionsprodukten und die Aktivierungsbarrieren der durchgeführten Reaktionen wurden mittels semiempirischer Verfahren (AM1) untersucht, um die beobachteten eindeutigen Regioselektivitäten zu interpretieren. Es zeigte sich, daß dafür nicht ausschließlich Frontorbitalkontrolle, sondern vor allem elektrostatische und sterische Wechselwirkungen verantwortlich sind.Die Spiroverbindungen4 wurden in weiterer Folge durch Reduktion zu den entsprechenden -Aminoalkoholen11 gespalten, welche wiederum zu Spiro-oxazinen des Typs12 und13 recyclisiert wurden. Die Verbindungen4 und9 sind ebenso wie12 und13 Derivate von neuen heterocyclischen Grundsystemen.

     

Theoretical Study of Mechanism and Regioselectivity of 1,3-dipolar Cycloaddition of N-[methyl]-C-[5-nitro-2-furyl] Nitrilimine with Dimethyl 7-oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylate

The mechanism and regioselectivity of 1,3-dipolar cycloaddition of N-[methyl]-C-[5-nitro-2-furyl] nitrilimine with dimethyl 7-oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylate were investigated using activation energy calculations and density functional theory-based re-activity indexes. The reaction proceeds by an asynchronous concerted mechanism. The calculations are performed at the B3LYP/6-31G(d) level of theory and the obtained results are in agreement with experimental outcome.