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%.

Synthese neuer Pyridin-C-nukleoside der 2 ,3 -Didesoxyribose durch „inverse“ [4+2]-Cycloaddition Synthesis of Novel Pyridine-C-nucleosides of 2,3-Dideoxyribose by „Inverse“ [4+2]-Cycloaddition

1997 ◽  
Vol 52 (7) ◽  
pp. 851-858 ◽  
Author(s):  
Gunther Seitz ◽  
Johanna Siegl
Keyword(s):  
Cycloaddition Reaction ◽  
Alder Reaction ◽  
Diels Alder ◽  
The Novel ◽  
Protecting Group ◽  
Enol Ethers ◽  
Inverse Electron Demand ◽  
Diels Alder Reaction ◽  
Cyclic Ketene Acetals

The anomeric imido esters 5 and 6, appropriate precursors for C-nucleoside synthesis, were prepared and utilized as heterodienophiles in a Diels-Alder reaction with inverse electron demand to yield the novel, protected 1.2.4-triazine C-nucleosides 8 and 9. They could be deprotected by treatment with 70% trifluoroacetic acid to furnish the free C-nucleosides 10 and 11. The triazine „aglycon“ of 8 contains an electron deficient diazadiene system, highly activated to react with various electron rich dienophiles such as enamines, enol ethers and several cyclic ketene acetals in an „inverse“ [4+2]-cycloaddition reaction. The Diels-Alder adducts spontaneously eliminate N2 and after follow-up reactions the O-TBDPS protected pyridine-C-nucleosides 13, 15, 17,19, 21 and 23 are formed. Removal of the protecting group by treatment with CF3CO2H /H2O leads to the corresponding 2’,3’-dideoxy-β-D-ribofuranosyl- pyridines.

scholarly journals Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

2015 ◽  
Vol 11 ◽  
pp. 576-582 ◽  
Author(s):  
Grzegorz Mlostoń ◽  
Paulina Grzelak ◽  
Maciej Mikina ◽  
Anthony Linden ◽  
Heinz Heimgartner
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Thermal Conditions ◽  
Alder Reaction ◽  
Diels Alder ◽  
Hydrogen Shift ◽  
Diels Alder Reaction ◽  
Shift Sequence

Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels–Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones.

Synthesis of endo-fused 5-unsubstituted hexahydro-2H-pyrano[3,2- c]quinolines via sequential Sc(OTf)3-catalyzed cationic imino-Diels-Alder Reaction/N-debenzylation using N-benzylanilines, 3,4-dihydro-2H-pyran and paraformaldehyde under MW irradiation

2021 ◽  
Vol 18 ◽  
Author(s):  
Arturo René Mendoza Salgado ◽  
Carlos Eduardo Puerto Galvis ◽  
Vladimir V. Kouznetsov ◽  
Carlos Mario Meléndez
Keyword(s):  
Efficient Method ◽  
Cycloaddition Reaction ◽  
Acid Catalyst ◽  
Alder Reaction ◽  
Diels Alder ◽  
Synthetic Methods ◽  
Diels Alder Reaction ◽  
Catalytic Transfer ◽  
Lewis Acid Catalyst ◽  
Mw Irradiation

Background: Hexahydro-2H-pyrano[3,2-c]quinolines are known to have antibacterial, antifungal, and antitumor properties. Great efforts have been made to develop new synthetic methods that lead to the synthesis of valuable libraries. Extensive methodologies, low yields, excessive amounts of catalyst and expensive reactants are some of the limitations of current methodologies. Aim and Objective: Developing a useful and efficient method to construct diversely substituted hexahydro-2H-pyrano[3,2- c]quinolines into good to excellent yields through a cationic imino-Diels-Alder/N-debenzylation methodology. Method: The cationic imino-Diels-Alder/N-debenzylation methodology was used for the preparation of substituted hexahydro-2H-pyrano[3,2-c]quinolines. It involves the use of Sc(OTf)3 for activation of cationic imino-Diels-Alder cycloaddition reaction of N-benzylanilines, 3,4-dihydro-2H-pyran and paraformaldehyde in MeCN; and microwave irradiation to shorten reaction time to afford new 6-benzyl-hexahydro-2H-pyrano[3,2-c]quinolines whose catalytic transfer debenzylation reactions with HCO2NH4 in the presence of Pd/C (10%) and methanol give the new 5-unsubstituted pyrano[3,2- c]quinolines in excellent yields. Results: We found that optimal conditions for the preparation of hexahydro-2H-pyrano[3,2-c]quinolines were Sc(OTf)3 0,5 % and acetonitrile at 160 ° C for 15 min; and using paraformaldehyde obtained the 6-benzyl-hexahydro-2H-pyrano [3,2- c]quinolines with excellent yields, while the N-debenzylation process using ammonium formate in the presence of Pd/C and methanol resulted in the synthesis of hexahydro-2H-pyrano [3,2-c] quinolines with quantitative yields (95-98%). Conclusion: We describe an efficient method to synthesize hexahydro-2H-pyrano[3,2-c]quinolines via the cationic iminoDiels-Alder/N-debenzylation methodology using Sc(OTf)3 0,5 % as Lewis Acid catalyst. Excellent yields of the products, using of MW irradiation, short times of reactions and an efficient and highly diversified method are some of the main advantages of this new protocol.

scholarly journals Coupling the Microscopic Healing Behaviour of Coatings to the Thermoreversible Diels-Alder Network Formation

Coatings ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 13 ◽  
Author(s):  
Joost Brancart ◽  
Robrecht Verhelle ◽  
Jessica Mangialetto ◽  
Guy Van Assche
Keyword(s):  
Network Formation ◽  
Polymer Network ◽  
Cycloaddition Reaction ◽  
Thermomechanical Properties ◽  
Alder Reaction ◽  
Diels Alder ◽  
Force Microscopy ◽  
Diels Alder Reaction ◽  
Atomic Force ◽  
Microscopic Evaluation

While thermally reversible polymer network coatings based on the Diels-Alder reaction are widely studied, the mechanisms responsible for the heating-mediated healing of damage is still not well understood. The combination of microscopic evaluation techniques and fundamental insights for the thermoreversible network formation in the bulk and coating shed light on the mechanisms behind the damage healing events. The thermomechanical properties of thermoset and elastomer coatings, crosslinked by the furan-maleimide Diels-Alder cycloaddition reaction, were studied in bulk and compared to the thermal behaviour applied as coatings onto aluminium substrates. The damage sealing of thermoset (Tg = 79 °C) and elastomer (Tg = −49 °C) coatings were studied using nano-lithography and atomic force microscopy (AFM). The sealing event is studied and modelled at multiple temperatures and correlated to the changes in the network structure and corresponding thermomechanical properties.

scholarly journals A theoretical study of the solvent effect on Diels-Alder reaction in room temperature ionic liquids using a supermolecular approach

2009 ◽  
Vol 123 (3-4) ◽  
pp. 347-352 ◽  
Author(s):  
Riccardo Bini ◽  
Cinzia Chiappe ◽  
Veronica L. Mestre ◽  
Christian S. Pomelli ◽  
Thomas Welton
Keyword(s):  
Ionic Liquids ◽  
Solvent Effect ◽  
Room Temperature ◽  
Theoretical Study ◽  
Alder Reaction ◽  
Diels Alder ◽  
Room Temperature Ionic Liquids ◽  
Diels Alder Reaction
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