1,4-Cycloaddition Reactions. The Diels-Alder Reaction in Heterocyclic Syntheses

1968 ◽  
Vol 11 (2) ◽  
pp. 408-408
Author(s):  
Francis Caren
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Cycloaddition Reactions ◽  
Diels Alder Reaction

scholarly journals Enhancing the reactivity of 1,2-diphospholes in cycloaddition reactions

2015 ◽  
Vol 11 ◽  
pp. 169-173 ◽  
Author(s):  
Almaz Zagidullin ◽  
Vasili Miluykov ◽  
Elena Oshchepkova ◽  
Artem Tufatullin ◽  
Olga Kataeva ◽  
...  
Keyword(s):  
Room Temperature ◽  
Cycloaddition Reaction ◽  
Alder Reaction ◽  
Diels Alder ◽  
Alkyl Halides ◽  
Ethyl Iodide ◽  
Para Position ◽  
Cycloaddition Reactions ◽  
Diels Alder Reaction ◽  
Heating Up

Two different approaches have been employed to enhance the reactivity of 1-alkyl-1,2-diphospholes – the introduction of electron-withdrawing groups either at the phosphorus atoms or in the para-position of the arene ring. The alkylation of sodium 1,2-diphospha-3,4,5-triphenylcyclopentadienide with alkyl halides Hal-CH2-R (R = CN, COOEt, OMe, CH2OEt) results in corresponding 1-alkyl-3,4,5-triphenyl-1,2-diphospholes (alkyl = CH2CN (1a), CH2COOEt (1b), CH2OMe (1c), and (CH2)2OEt (1d)), which spontaneously undergo the intermolecular [4 + 2] cycloaddition reactions at room temperature to form the mixture of the cycloadducts, 2a–c, respectively. However the alkylation of sodium 1,2-diphospha-3,4,5-tri(p-fluorophenyl)cyclopentadienide with ethyl iodide leads to stable 1-ethyl-3,4,5-tris(p-fluorophenyl)-1,2-diphosphole (1e), which forms the [4 + 2] cycloadduct 2,3,4,4a,5,6-hexa(p-fluorophenyl)-1-ethyl-1,7,7a-triphospha-4,7-(ethylphosphinidene)indene (2e) only upon heating up to 60 °C. With further heating to 120 °C with N-phenylmaleimide, the cycloadducts 2a–c and 2e undergo the retro-Diels–Alder reaction and form only one product of the [4 + 2] cycloaddition reaction 3a–с, 3e with good yields up to 65%.

scholarly journals Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

2021 ◽  
Vol 17 ◽  
pp. 719-729
Author(s):  
Ramazan Koçak ◽  
Arif Daştan
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Cycloaddition Reactions ◽  
Inverse Electron Demand ◽  
Diels Alder Reaction ◽  
Reductive Treatment ◽  
High Yields ◽  
Derivatives Of ◽  
Electron Demand

The synthesis of novel polycyclic π-conjugated dihydropyridazines, pyridazines, and pyrroles was studied. Dihydropyridazine dyes were synthesized by inverse electron-demand Diels–Alder cycloaddition reactions between a dibenzosuberenone and tetrazines that bear various substituents. The pyridazines were synthesized in high yields by oxidation of dihydropyridazine-appended dibenzosuberenones with PIFA or NO. p-Quinone derivatives of pyridazines were also obtained by H-shift isomerization following the inverse electron-demand Diels–Alder reaction of tetrazines with p-quinone dibenzosuberenone. Then these pyridazines were converted to the corresponding pyrroles by reductive treatment with zinc. It was observed that all the dihydropyridazines obtained gave absorbance and emission at long wavelengths.

Establishing a library of porphyrin building blocks for superstructured assemblies: porphyrin dienes and dienophiles for cycloaddition reactions

2002 ◽  
Vol 06 (11) ◽  
pp. 673-684 ◽  
Author(s):  
Maxwell J. Gunter ◽  
Hesheng Tang ◽  
Ronald N. Warrener
Keyword(s):  
Building Blocks ◽  
Conformational Flexibility ◽  
Alder Reaction ◽  
Diels Alder ◽  
Cycloaddition Reactions ◽  
Mild Oxidation ◽  
Diels Alder Reaction ◽  
Cyclohexene Ring ◽  
Ready Access ◽  
Thermal Extrusion

The synthesis and utility of a series of porphyrins with (masked) diene and dienophile functionality are described. The key porphyrin diene is synthesised from a sulfolenopyrrole by a 3+1 strategy. A range of Diels-Alder cycloadducts is readily accessed from the diene by mild thermal extrusion of sulfur dioxide from the sulfolenoporphyrin, which produces the reactive porphodimethylidene. Each of these cycloadducts is fused to the porphyrin nucleus through a cyclohexene ring thus retaining some conformational flexibility in the resultant structures. The structures can be rigidified by mild oxidation to the corresponding benzo-derivatives. Diels-Alder reaction of the porphyrin 1,3-diene resulting from the sulfolenoporphyrin with norbornadiene produces the norbornene derivative, which can serve as a dienophile or dipolarophile in subsequent cycloaddition reactions. Nevertheless, a preferred route to this structure is through a corresponding 1+3 route, where the norbornene component is part of the tripyrrane. Extension of the synthetic protocols allows ready access to a “mixed function” porphyrin, containing both diene and dienophile components. Likewise, the synthesis of a bis-norbornene porphyrin is described. A collection of each of these reactive components is the basis for a library of building blocks which allows easy and simple entry to a wide variety of complex porphyrin-containing superstructures.

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