scholarly journals A Natural Diels‐Alder Biocatalyst Enables Efficient [4+2] Cycloaddition Under Harsh Reaction Conditions

ChemCatChem ◽  
2019 ◽  
Vol 11 (20) ◽  
pp. 5027-5031 ◽  
Author(s):  
Carl O. Marsh ◽  
Nicholas R. Lees ◽  
Li‐Chen Han ◽  
Matthew J. Byrne ◽  
Sbusisiwe Z. Mbatha ◽  
...  
Keyword(s):  
Diels Alder ◽  
Reaction Conditions

Single wall carbon nanotube (SWCNT)–gold nanorod (AuNR) conjugates via thermally-mild reaction conditions

2017 ◽  
Vol 41 (21) ◽  
pp. 12392-12396 ◽  
Author(s):  
Siting Ni ◽  
Jun Zhu ◽  
Mohamed Amine Mezour ◽  
R. Bruce Lennox
Keyword(s):  
Carbon Nanotube ◽  
Covalent Binding ◽  
Alder Reaction ◽  
Diels Alder ◽  
Gold Nanorod ◽  
Reaction Conditions ◽  
Single Wall Carbon ◽  
Inverse Electron Demand ◽  
Diels Alder Reaction ◽  
Electron Demand

A thermally-mild method for covalent binding of SWCNTs to AuNRs, based on an inverse-electron-demand Diels–Alder reaction, is established and discussed.

Einfache Synthese von 2,2-Diethoxy-2,5-dihydrofuranen, 2(5 H)Furanonen und 2-Ethoxy-furanen.Kristall-und Molekülstruktur eines Barrelenon Diels-Aider Produktes [1] / Convenient Synthesis of 2,2-Diethoxy-2,5-dihydrofurans, 2(5 H)Furanones and 2-Ethoxyfurans.Crystal and Molecular Structure of a Barrelenone Diels-Alder Product [1]

1994 ◽  
Vol 49 (3) ◽  
pp. 389-406 ◽  
Author(s):  
Rolf W. Saalfrank ◽  
Wieland Hafner ◽  
Joachim Markmann ◽  
Andreas Welch ◽  
Karl Peters ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Maleic Anhydride ◽  
Structure Analysis ◽  
Diels Alder ◽  
Dimethyl Acetylenedicarboxylate ◽  
Reaction Conditions ◽  
X Ray ◽  
Convenient Synthesis

AbstractReaction of 1,2-hydroxyketones 5 with (2,2-diethoxyvinylidene)triphenylphosphorane (2) or (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborates 6 yields the 2,2-diethoxy- 2.5-dihydrofurans 9. Depending on the reaction conditions used, the orthoesters 9 can be hydrolized to give 2(5 H)furanones 10 and 2-ethoxyfurans 11, respectively. 4,5-Dimethyl- 5.6-dihydro-2-pyranone (20) and 8-methoxycoumarin (23) are prepared, starting from (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborate (6 a) and 1-hydroxy-2-methyl- 3-butanone (16) or 2-hydroxy-3-methoxy-benzaldehyde (21). The 2-ethoxyfuranes 11 readily undergo Diels-Alder reactions with 2-chloracrylonitrile (24), maleic anhydride (26), N-phenyl-1,2,4-triazoline-3,5-dione (28) and dimethyl acetylenedicarboxylate (30) to give the corresponding Diels-Alder products 25, 27, 29 and 31, respectively. Contrary to 2-ethoxyfuran 11b , 11a reacts with two equivalents of acetylene 30, to yield barrelenone 34. The structure of 34 unequivocally is established by X-ray structure analysis.

scholarly journals Direct Diels-Alder reaction of chitin derived 3-acetamido-5-acetylfuran

2022 ◽  
Author(s):  
Rafael Gomes ◽  
Juliana Pereira ◽  
João Ravasco ◽  
João Vale ◽  
Fausto Queda
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Fine Tuning ◽  
Reduced Form ◽  
Partial Hydrolysis ◽  
Reaction Conditions ◽  
Diels Alder Reaction ◽  
Direct Use ◽  
Kinetics Of ◽  
Hydrolysis Of

The Diels-Alder (DA) reaction of biomass derived furans is an emerging technology for the preparation of new molecular entities and “drop-in” commodity chemicals. In this work we address the challenge of the direct use of electron-poor furanic platforms as dienes through the use of an unexplored chitin derived furan, 3-acetamido-5-acetylfuran (3A5AF). The 3-acetamido group promoted a remarkable increase in the kinetics of the DA allowing for the preparation of 7-oxanorbornenes (7-ONB) at 50 ºC. Partial hydrolysis of the enamide to hemi-acylaminals was possible upon fine tuning of the reaction conditions, disabling retro-DA processes. Finally, DA reaction of the reduced form of 3A5AF allowed quantitative formation of 7-ONB in aqueous condition after 10 minutes. Certanly these are the first steps for expanding the toolbox of chitin derived 3A5AF as diene.

COS-triggered Oxygen/Sulfur Exchange of Isatins: Chemoselective Synthesis of Functionalized Isoindigos and Spirothiopyrans via Self-condensation and Thio-Diels-Alder Reaction

2022 ◽  
Author(s):  
Wei Chen ◽  
Hui Zhou ◽  
Bai-Hao Ren ◽  
Wei-Min Ren ◽  
Xiaobing Lu
Keyword(s):  
Exchange Reaction ◽  
Sulfur Atom ◽  
Carbonyl Sulfide ◽  
Alder Reaction ◽  
Diels Alder ◽  
Reaction Conditions ◽  
Diels Alder Reaction ◽  
Chemoselective Synthesis ◽  
Sulfur Exchange

Herein, we present the first organocatalytic oxygen/sulfur atom exchange reaction (O/S ER) of isatins by employing carbonyl sulfide (COS) as novel sulfuring reagent under mild reaction conditions. 8-Diazabicyclo[5.4.0] undec-7-ene (DBU),...

Intramolecular Diels–Alder reactions of 2H-thiopyran dienes

1996 ◽  
Vol 74 (7) ◽  
pp. 1418-1436 ◽  
Author(s):  
Dale E. Ward ◽  
Thomas E. Nixey ◽  
Yuanzhu Gai ◽  
Matthew J. Hrapchak ◽  
M. Saeed Abaee
Keyword(s):  
Lewis Acid ◽  
Acid Catalysis ◽  
Thermal Conditions ◽  
Sigmatropic Rearrangement ◽  
Diels Alder ◽  
Methyl Groups ◽  
Type Ii ◽  
Reaction Conditions ◽  
Terminal Olefin ◽  
High Stereoselectivity

A systematic survey of IMDA reactions of 4-[tris(2-methylethyl)silyl]oxy-2H-thiopyran derivatives with potential dienophiles tethered at the C-2, C-3, C-5, and C-6 positions is presented. Cycloaddition was not observed with a C3 or C4 tether and an unactivated terminal olefin as dienophile. IMDA adducts could be obtained when dienophiles activated by a carbomethoxy group were employed. Compounds having the activated dienophile attached via a C3 tether to C-2 of the 2H-thiopyran gave adducts with high stereoselectivity. Substrates having the dienophile attached to C-3 with a C3 or C4 tether cyclized readily. With an (E)-enoate as the dienophile, the stereoselectivity was poor (endo:exo = 1.1–2.5:1) and essentially independent of reaction conditions (i.e., thermal vs. Lewis acid mediated). With the(Z)-enoate, a 7:1 mixture of endo:exo IMDA adducts was obtained under thermal conditions; with Lewis acid catalysis, isomerization of the dienophile was competitive with cycloaddition. Type II IMDA adducts were not observed with C-5 tethered substrates. Compounds having the dienophile attached to C-6 via a C3 or a five-atom tether also failed to give IMDA adducts. No evidence for isomerization of the 2H-thiopyran dienes by [1,5] sigmatropic rearrangement was observed. The endo adducts from IMDA reactions of the C-3 tethered substrates can be desulfurized to obtain synthetically useful trans-fused hydrindans and decalins with angular methyl groups. Key words: intramolecular Diels–Alder, 2H-thiopyran, cis-substituted 1,3-diene surrogate, trans-octahydro-3a-methyl-1H-indene derivatives, trans-decahydro-4a-methylnapthalene derivatives.

scholarly journals Asymmetric Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene

2012 ◽  
Vol 8 ◽  
pp. 1819-1824 ◽  
Author(s):  
Magnus Rueping ◽  
Sadiya Raja
Keyword(s):  
Alder Reaction ◽  
Optically Active ◽  
Diels Alder ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Reaction Conditions ◽  
Diels Alder Reaction ◽  
Brönsted Acid ◽  
Acid Catalyzed ◽  
Chiral Bronsted Acid

A new chiral Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene has been developed. The reaction provides optically active aza-tetracycles in good yields with high diastereo- and enantioselectivities under mild reaction conditions.

Diels–Alder reactions of activated 2H-thiopyrans

1991 ◽  
Vol 69 (10) ◽  
pp. 1487-1497 ◽  
Author(s):  
Dale E. Ward ◽  
Yuanzhu Gai ◽  
Wajdi M. Zoghaib
Keyword(s):  
Thermal Decomposition ◽  
Key Words ◽  
Diels Alder ◽  
Reaction Conditions ◽  
Approximate Order

The Diels–Alder reactivity of various 2H-thiopyrans bearing electron-donating substituents has been investigated. The approximate order of reactivity among the 2H-thiopyrans studied was 4,6-disubstituted [Formula: see text] 5-substituted > 4-substituted, 3,5-disubstituted [Formula: see text] 3-substituted. Good yields of predominantly endo adducts are obtained with reactive dienophiles. With less reactive dienophiles, reactions are much slower and yields are attenuated due to the competing thermal decomposition of the dienes under the reaction conditions. The adducts obtained are equivalent (via desulfurization) to those from unreactive cis-substituted dienes. Key words: Diels–Alder, 2H-thiopyran.

Reaction of Bromonaphthofurans with Bis(pinacolato)diboron.

1999 ◽  
Vol 52 (11) ◽  
pp. 1021 ◽  
Author(s):  
Margaret A. Brimble ◽  
Fatiah Issa
Keyword(s):  
Late Stage ◽  
Diels Alder ◽  
Aryl Bromide ◽  
Reaction Conditions ◽  
Boronate Ester ◽  
Oxidative Rearrangement ◽  
Biaryl Coupling ◽  
Claisen Reaction

The synthesis of a dimeric pyranonaphthoquinone (8) was investigated focusing on a late-stage biaryl coupling of suitably functionalized bromonaphthofurans by using Suzuki–Miyaura methodology. Bromonaphthofuran (16) underwent reaction with bis(pinacolato)diboron in the presence of PdCl2(dppf) to afford boronate ester (21) and furonaphthofuran (22). ‘In situ’coupling of the boronate ester (21) with aryl bromide (16) to the desired dimer (11) was not realized. Bromonaphthofuran (17), prepared by Diels–Alder/retro-Claisen reaction of bromonaphthoquinone (24) with diene (25), underwent Suzuki–Miyaura coupling to naphthofuran (27) and boronate ester (28). Numerous attempts to alter the reaction conditions to effect homocoupling of bromide (17) to biaryl (19) were unsuccessful. Bromopyranonaphthoquinone (18) prepared by oxidative rearrangement of (17) failed to undergo Suzuki–Miyaura coupling.

Thermal Routes to Substituted Cyclopentadienes

1972 ◽  
Vol 50 (19) ◽  
pp. 3186-3195 ◽  
Author(s):  
D. M. Findlay ◽  
Marie Lessard Roy ◽  
Stewart McLean
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Thermal Process ◽  
Kinetic Studies ◽  
Alder Reaction ◽  
Diels Alder ◽  
Reaction Conditions ◽  
Phenyl Azide ◽  
Aromatic Fragment ◽  
Diels Alder Reaction

An investigation has been made with the aim of finding a route to cyclopentadienes, particularly those with a single substituent at the 5-position, in which the final step is a thermal process of low enough activation energy that the cyclopentadiene produced does not undergo rearrangement by hydrogen migration under the reaction conditions. In the routes studied the final intermediates have been suitably substituted norbornenes which can lead to the required cyclopentadiene and an aromatic fragment by a retro-Diels–Alder reaction. In one series the intermediate was a phenyl azide adduct of norbornadiene which fragmented to cyclopentadiene and phenyltriazole, but the temperature required for this was clearly too high to allow substituted cyclopentadienes to be isolated before they had rearranged. In the course of this work, in addition to the exo-adduct of phenyl azide, the endo-adduct and a number of bisadducts were obtained and studied. In another series, adducts of tetraphenylcyclopentadienone and dimethyldiphenylcyclopentadienone with norbornadiene and 7-phenylnorbornadiene were prepared and studied. Decarbonylation of the adducts was effected both thermally and photochemically; in the latter case the reaction could be carried out at low temperature and the dihydrobenzene (a dihydrobenzonorbornadiene) produced was isolable. With or without isolation, the dihydrobenzene underwent a subsequent retro-Diels–Alder reaction to provide the cyclopentadiene and a substituted benzene. Kinetic studies showed that the activation energy for this process was almost but not quite low enough to satisfy the conditions stipulated, and in no case was a 5-substituted cyclopentadiene isolated before it had rearranged.

Caveat in the stereochemical outcome of the organocatalytic Diels–Alder reaction in PEG-400

RSC Advances ◽  
2016 ◽  
Vol 6 (80) ◽  
pp. 76132-76136 ◽  
Author(s):  
Pantapalli M. Anitha ◽  
Prathama S. Mainkar ◽  
Shivakrishna Kallepu ◽  
V. S. Phani Babu ◽  
Cirandur Suresh Reddy ◽  
...  
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Reaction Conditions ◽  
Peg 400 ◽  
Diels Alder Reaction

The organocatalytic Diels–Alder reaction in non-conventional solvent (PEG-400) has yielded cycloaddition products with diastereoselectivities hitherto not reported in detail using classical reaction conditions.

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