Cycloadditions of Aryl‐Substituted 1,2,4‐Triazines with 2‐Cyclopropylidene‐1,3‐dimethylimidazolidine – Zwitterions as Discrete Intermediates

Cycloadditions of 2‐cyclopropylidene‐1,3‐dimethylimidazolidine ( 1 ), a strong, electron‐rich C‐nucleophile, with a variety of aryl‐substituted 1,2,4‐triazines occur at temperatures between ?100 and +100°, depending on the substitution pattern. At low temperatures, zwitterions, formed by nucleophilic attack of 1 on the triazines, could be detected spectroscopically and, in some cases, isolated. Two types of zwitterions were found: 1) those where the new bond was linked to C(5) of the triazine and which were formed in a reversible dead‐end equilibrium, and 2) those where the new bond was linked either to C(3) or C(6). The latter exhibited the same regiochemistry as the final cycloadducts, and might be intermediates of a two‐step Diels–Alder reaction. Energies and structural characteristics for stationary points in the reaction of monosubstituted triazines with 1 in the gas phase and in CH₂Cl₂ solution were calculated at the Becke3LYP/6‐311+G(d,p)//Becke3LYP/6‐31G(d) level of theory. Different reaction mechanisms are discussed on the basis of steric, electronic, and solvent effects.     

1,3-Dipolar Cycloaddition of 5-Substituted-1-Methyl-3-Oxidopyridiniums

5-Methoxy- and 5-dimethylamino-1-methyl-3-oxidopyridiniums were shown to give the 1,3-dipolar cycloadducts widely with methyl acrylate, acrylonitrile, N-phenylmaleimide, styrene, phenylacetylene, cyclopentadiene, cyclopentene, diethyl azodicarboxylate and singlet oxygen.     

Conjugation of 1-Aminoadamantanes and 5-Trifluoromethylhydantoins by 1,3-Dipolar Cycloaddition

Russian Journal of General Chemistry - A synthetic approach was proposed for combining pharmacophore scaffolds, namely, 1-aminoadamantanes and 5-trifluoromethylhydantoins by the copper-catalyzed...     

Some Aspects of the Azide-Alkyne 1,3-Dipolar Cycloaddition Reaction

Russian Journal of Organic Chemistry - Some peculiar features of two most commonly used catalytic systems (Cul and CuSOVsodium ascorbate) controlling the regioselectivity of 1,3-dipolar...     

Approach to the Valorization of Carbohydrates as Raw Materials by Microwave-Assisted Neat 1,3-Dipolar Cycloaddition

By reaction of C,N-diphenylnitrone and carbohydrates with a crotonyl side chain at their primary or anomeric carbon position, we explore the application of sugar derivatives as raw materials and chiral inducers in microwave-assisted neat 1,3-dipolar cycloadditions.     

微波促进的1,3-偶极环加成4β-1,2,3-三唑鬼臼毒素的合成

在微波作用的无溶剂条件下，由4β-叠鬼臼毒素与炔烃反应，合成了8个含有 1,2,3-三唑的鬼臼毒素衍生物，并用IR, ~1H NMR, MS确定了这些化合物的结构。 该反应操作简单，产率较高，副产物少，同时具有原子经济性。     

First Example of 1,3-Dipolar Cycloaddition of Carbonyl Ylides to Cyclopropenes

Carbonyl ylide generated from 1-diazo-5-phenylpentane-2,5-dione in the presence of Rh₂(OAc)₄ reacts with 3-substituted cyclopropenes following the 1,3-dipolar cycloaddition pattern to afford substituted 9-oxatricyclo[3.3.1.0^2,4]nonan-6-ones.     

Theoretical Study of 1,3-Dipolar Cycloaddition of Hydrazoic Acid to Substituted Ynamines

The 1,3-dipolar cycloaddition reactions of various substituted ynamines with hydrazoic acid were theoretically investigated with the high-accuracy CBS-QB3 method. Two regioisomers, 4-amine, and 5-amine substituted adducts, were obtained, with the former as the preferred yield. This regioselectivity is rationalized by the frontier molecular orbital theory. The reactivity and synchronicity are enhanced with the increase of the electron-withdrawing character of the substitute on ynamine fragment. The calculations also show that the effect of solvent increases the activation energy, and the reaction becomes even harder in polar solvent.     

Preparation of 1,3-Disubstituted-5-cyano-4,5-dihydropyrazoles via 1,3-Dipolar Cycloaddition of Nitrile Imine with Acrylonitrile

Ｉｎｔｒｏｄｕｃｔｉｏｎ4 ,5 Ｄｉｈｙｄｒｏｐｙｒａｚｏｌｅｄｅｒｉｖａｔｉｖｅｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｅｘｔｅｎｓｉｖｅｌｙｄｕｅｔｏｔｈｅｉｒｄｉｖｅｒｓｅｃｈｅｍｉｃａｌｒｅａｃｔｉｖｉｔｙ ,ｂｒｏａｄｓｐｅｃｔｒｕｍｏｆｂｉｏｌｏｇｉｃａｌａｃｔｉｖｉｔｙａｎｄｖａｒｉｅｔｙｏｆｉｎｄｕｓｔｒｉａｌａｐ ｐｌｉｃａｔｉｏｎ .1Ｉｎａｄｄｉｔｉｏｎ ,ｉｔｉｓｋｎｏｗｎｔｈａｔ 4 ,5 ｄｉｈｙｄｒｏｐｙｒａ ｚｏｌｅｄｅｒｉｖａｔｉｖｅｓｗｅｒｅｕｓｅｆｕｌｃｏｍｐｏｕｎｄｓｎｏｔｏｎｌ…     

氧化腈与丙炔1,3-偶极环加成反应中区域选择性的理论研究

用密度泛函(DFT)B3LYP/6-311＋＋G**方法研究了氧化腈(RCNO, R＝F, NO₂, OCH₃, OH, COOCH₃, CHO, CONH₂, H, CH₃)与丙炔的1,3-偶极环加成反应, 并且计算了不同温度下的反应速率常数, 讨论了氧化腈上不同取代基R的取代效应和温度对反应区域选择性的影响. 结果显示, 氧化腈与富电子亲偶极体——炔烃反应, 5-取代反应占优势; 氧化腈上取代基R为强吸电子基团时或在较高温度下, 有利于4-取代反应的进行.