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.

A synthesis and some reactions of 7-Oxabicyclo[2.2.1]heptan-2-one

1983 ◽  
Vol 36 (12) ◽  
pp. 2473 ◽  
Author(s):  
J Moursounidis ◽  
D Wege
Keyword(s):  
Thermal Decomposition ◽  
Alder Reaction ◽  
Diels Alder ◽  
Acid Mixture ◽  
Diels Alder Reaction ◽  
Reaction Proceeds ◽  
Atom Migration ◽  
Acyl Azide ◽  
Mild Hydrolysis ◽  
Hydrolysis Of

Diels-Alder reaction between furan and α-chloroacrylonitrile gives a mixture of exo-2-chloro-and endo-2-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitrile (4) and (5). Mild hydrolysis affords the corresponding α-chloro acid mixture, from which the endo carboxylic acid may be removed through iodo lactone formation. Catalytic hydrogenation of (4) and (5) followed by hydrolysis, acyl azide formation, Curtius rearrangement, and hydrolysis of the resulting mixture of a-chloro isocyanates yields 7-oxabicyclo[2.2.l]heptan-2-one (1) in preparatively useful amounts. Reduction of (1) gives only endo alcohol, and Baeyer-Villiger reaction proceeds with exclusive bridgehead atom migration. Thermal decomposition of the sodium salt of the p-toluenesulfonylhydrazone of (1) affords 7-oxatricyclo[2.2.1 .02,6]heptane.

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.

Preparation of YBa2Cu3O7−x precursors from a fused eutectic of sodium and potassium hydroxides

1989 ◽  
Vol 4 (6) ◽  
pp. 1307-1311 ◽  
Author(s):  
Nicholas Coppa ◽  
Daniel H. Nichols ◽  
John W. Schwegler ◽  
J. E. Crow ◽  
G. H. Myer ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Potassium Hydroxide ◽  
Product Formation ◽  
Mechanical Grinding ◽  
Reaction Conditions ◽  
Fine Powders ◽  
Yttrium Barium ◽  
Sodium And Potassium

A method for preparing YBa2Cu3O7−x from the simultaneous thermal decomposition of the nitrates of yttrium, barium, and copper in an anhydrous fused eutectic of sodium and potassium hydroxide is described. This method eliminates the need for any mechanical grinding or the introduction of carbon containing anions. Products formed are fine powders (∼1 μm) having mole ratios 1.00Y:2.00Ba:3.06Cu.X-ray diffraction analyses reveal that the initial products are Y(OH)3, BaO2, and CuO, which when air calcinated/oxygen annealed at 900–950 °C form the superconducting YBa2Cu3O7−x A mechanism is postulated for product formation as a function of reaction conditions.

Acyl cyanides as carbonyl heterodienophiles: application to the synthesis of naphthols, isoquinolones, and isocoumarins

1996 ◽  
Vol 74 (2) ◽  
pp. 221-226 ◽  
Author(s):  
Richard Connors ◽  
Elisabeth Tran ◽  
Tony Durst
Keyword(s):  
Key Words ◽  
Diels Alder ◽  
Acetonitrile Solution ◽  
Carbon And Nitrogen ◽  
Nitrogen Nucleophiles ◽  
Derivatives Of

Irradiation of 2-methylbenzoyl cyanide (3a) in acetonitrile solution results in the formation of its dimer, which upon loss of HCN gives rise to the cycloadduct 7a. The dimerization also proceeds efficiently with derivatives of 3a giving adducts 7b and 7c. When 2-methylaroyl cyanides are photolyzed in the presence of a more reactive acyl cyanide the mixed adducts 8a–e are obtained in excellent yields. The cycloadducts 7a–c and 8a–e react with carbon and nitrogen nucleophiles by a tandem addition–cyclization sequence furnishing substituted naphthols (10a and 10b) and isoquinolones (11a–d), respectively. Isocoumarins 12a and 12b were prepared from the adducts 8a and 8e by treatment with potassium tert-butoxide in THF. Key words: naphthols, isoquinolones, isocoumarins, synthesis of; acyl cyanides; hetero Diels–Alder.

4-Aryl-3-substituted Furans

1994 ◽  
Vol 59 (12) ◽  
pp. 2721-2726 ◽  
Author(s):  
Jarmila Štetinová ◽  
Ján Leško ◽  
Miloslava Dandárová ◽  
Rudolf Kada ◽  
Roman Koreň
Keyword(s):  
Thermal Decomposition ◽  
Triple Bond ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Substituted Furans

4-Aryl-3-substituted furans IIIa - IIId were prepared by Diels Alder reaction of 4-phenyloxazole (I) with compounds IIa - IId, containing an activated triple bond, and subsequent thermal decomposition of the cycloadduct.

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

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.

Dihydrothiophenes.10. The preparation and Diels–Alder reactions of some sulfur and phosphorus-substituted dienophiles and 2-aza-substituted 1,3-dienes

1984 ◽  
Vol 62 (11) ◽  
pp. 2089-2093 ◽  
Author(s):  
John M. McIntosh ◽  
Lilianna Z. Pillon
Keyword(s):  
Thermal Decomposition ◽  
Alder Reaction ◽  
Conjugated Dienes ◽  
Diels Alder ◽  
Diels Alder Reaction

The use of 3-carboxylated 2,5-dihydrothiophenes as the dienophilic component of the Diels–Alder reaction has been investigated. The yields are generally quite low. The formation of conjugated dienes that are aminated at an interior position of the conjugated chain by formation and thermal decomposition of 3-acetamido-2,5-dihydrothiophenes appears to be a viable route to these useful compounds. One example of the Diels–Alder reaction of 2-carboxylated diethyl vinylphosphonates is reported.

The thermal decomposition of diethyl ether. II. Analytical survey of the reaction products as a function of reaction conditions

1958 ◽  
Vol 245 (1240) ◽  
pp. 40-48 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Rate Constants ◽  
Vapour Phase ◽  
Mass Spectrometric ◽  
Spectrometric Analysis ◽  
Reaction Products ◽  
Reaction Conditions ◽  
True Rate ◽  
Carbon Tetrafluoride ◽  
Pressure Changes

By mass-spectrometric analysis combined with vapour-phase chromatography the reaction products from the thermal decomposition of ether have been determined at various stages of the reaction (uninhibited and inhibited by nitric oxide) for initial ether pressures of 80 to 1000 mm. The effects of added hydrogen and of carbon tetrafluoride on the composition of the products have also been examined. No major changes in the chemistry of the reaction occur with these variations in conditions. Factors are given for calculating true rate constants from pressure changes accompanying the reaction. Corrected values of rate constants vary with the conditions in the same way as the values derived from uncorrected pressure changes, the correspondence being close for the uninhibited reaction.

ISOBENZOFURANE, A TRANSIENT INTERMEDIATE

1965 ◽  
Vol 43 (5) ◽  
pp. 1599-1606 ◽  
Author(s):  
Louis F. Fieser ◽  
Makhluf J. Haddadin
Keyword(s):  
Thermal Decomposition ◽  
Diels Alder ◽  
Independent Synthesis ◽  
Trapping Agent ◽  
Transient Intermediate

A study of Diels–Alder reactions of tetraphenylcyclopentadienone (II) coupled with development of two improved procedures for the generation of benzyne, one of which affords a practical route to the reactive dienophile 1,4-dihydronaphthalene-1,4-endo-oxide (Ia), led to an investigation of the reaction of Ia and II. At 80° these reactants combine readily to give the adduct IIIa, which is cleaved on pyrolysis to isobenzofurane VIIIa and 1,2,3,4-tetraphenylbenzene (IX). The transient existence of isobenzofurane (VIIIa) was established by trapping it with the 1,4-endo-oxide Ia and isolation of the adducts X and XI. In confirmation of the interpretation, X and XI were obtained by independent synthesis from the adduct Va from Ia and α-pyrone and thermal decomposition of Va in the presence of Ia as trapping agent. Parallel experiments with 1,4-dimethyl-1,4-dihydronaphthalene-1,4-endo-oxide, as well as mixed additions, supported the interpretations advanced. Evidence is presented to show that isobenzofurane (VIIIa) invariably adds exo to the bicyclic dienophile.

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