Conformational analysis about the N-N bond by P.M.R. spectroscopy: N'-derivatives of N-amino-1,2,3,4-tetrahydro-9-oxo-1,4-ethanonaphthalene-endo-2,3-dicarboximide

1973 ◽  
Vol 26 (9) ◽  
pp. 1963 ◽  
Author(s):  
SM Verma ◽  
O Subba Rao
Keyword(s):  
Maleic Anhydride ◽  
Conformational Analysis ◽  
Conformational Changes ◽  
Major Product ◽  
Diels Alder ◽  
Conformational Study ◽  
Temperature Dependent ◽  
Spectral Changes ◽  
Derivatives Of

A series of N?-derivatives of N-amino-1,2,3,4-tetrahydro-9-oxo-1,4- ethanonaphthalene-endo-2,3-dicarboximide have been prepared and their p.m.r. spectra studied. The non-planar ?cage-moiety? structure has been used in the conformational study. Temperature dependent spectral changes have been related to conformational changes about the N-N bond. ��� The endo configuration of the major product obtained in Diels-Alder addition of maleic anhydride on β-naphthol has been strongly evidenced.

Conformational analysis about the N-N bond by N.M.R. spectroscopy: N'-sulphonyl derivatives of N-Aminobicyclo[2,2,1]hept-5-ene-endo-2,3-dicarboximide

1974 ◽  
Vol 27 (6) ◽  
pp. 1227 ◽  
Author(s):  
SM Verma ◽  
Rao C Koteswara
Keyword(s):  
Conformational Analysis ◽  
Conformational Changes ◽  
Ground States ◽  
Spectral Changes ◽  
Rotational Barriers ◽  
Tosyl Group ◽  
Derivatives Of ◽  
Acyl Derivatives

A series of N'-sulphonyl and N'-acyl derivatives of N-aminobicyclo[2,2,1]hept-5-ene-endo-2,3-dicarboximide have been synthesized and their conformations have been investigated by N.M.R.spectroscopy. The effect of the sulphonyl group at the exocyclic nitrogen on the conformational process about the N-N bond has been studied. Existence of non-planar ground states about the N-N bond in the N',N?-disulphonyl and N'-sulphonyl-N'-acyl derivatives has been demonstrated.Temperature-dependent spectral changes have been related to the conformational changes about the N-N bond. It has been shown that the N'-tosyl substituent assumes a preferred conformation about the N-SO2 bond; the aryl part of the tosyl group lies exo to the cage-moiety. The N'-tosyl-N'-aroyl derivatives also show a preferred conformation about the N'-aroyl bond, the aryl part of the aroyl group lying endo to the cage-moiety. The N'-acetyl-N'-aroyl derivatives have been shown toexhibit low rotational barriers about the N'-aroyl bond.

scholarly journals Lineare Oligophosphaalkane, XX [1]: Alkalimetall-und Trimethylsilylderivate PH-funktioneller Methylenbisphosphane / Linear Oligophosphaalkanes, XX [1]: Alkali Metal and Trimethylsilyl Derivatives of PH-Functional Methylenebisphosphanes

1988 ◽  
Vol 43 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Franjo Gol ◽  
Gerd Hasselkuß ◽  
Peter C. Knüppel ◽  
Othmar Stelzer
Keyword(s):  
Conformational Changes ◽  
Coupling Constants ◽  
Protecting Groups ◽  
Temperature Dependent ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Trimethylsilyl Derivatives ◽  
First Time ◽  
Derivatives Of ◽  
Association Equilibrium

Abstract The synthesis of the trimethylsilyl derivatives of the PH-functional methylenebisphosphanes, R2-n(Me3 Si)nP-CH2 -PR(SiMe3) (R = Me, iPr, tBu, Ph, 2.4.6-Me3C6H2 ; n = 0.1) is reported. In the Li-phosphides R2-nLinP - CH2 - PLiR used as reactive intermediates, a monomer-oligomer association equilibrium causes a rapid Li-exchange as indicated by the solvent and temperature dependent 31P{1H} and 7Li NMR spectrum of (iPr)2 P-CH2 -P(iPr)Li in various solvents (Et2O, THF and MTHF) in the temperature range from 30 to -110 °C. For the syntheses of the Me-and Ph-substituted PH-functional methylenebisphosphanes R2P-CH2 -PRH and RHP-CH2 -PRH (R = Me, Ph) the chlorophosphane CKP -CH2 -PCl2 is used as a starting material. Bifunctional substituents (Ph -N̍-N̍ -Ph and Me -N̍-CO-N̍-Me) are employed for the first time as protecting groups to block one or two PCl-functions in Cl2P-CH2-PCI2,. Cleavage of the PN-bonds in the five membered ring systems (R = Me, Ph) with HCl affords the P-substituted methylenebis-chlorophosphanes RClP-CH2 - PClR in satisfactory yields. The compounds have been characterized by 1H, 13 C{1H} and 31P{1H} NMR spectroscopy. With-in homologous substitution series of methylenebisphosphanes, e.g. R2P-CH2-PR2-nHnthe coupling constants 2J(PP) seem to reflect conformational changes at the PCP-skeleton.

scholarly journals Structural and solvent control over activation parameters for a pair of retro Diels-Alder reactions

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Andrea L. Widstrom ◽  
Benjamin J. Lear
Keyword(s):  
Maleic Anhydride ◽  
Activation Parameters ◽  
Solvent Polarity ◽  
Alder Reaction ◽  
Diels Alder ◽  
Temperature Dependent ◽  
Experimental Conditions ◽  
Click Reactions ◽  
Solvent Dependence ◽  
Solvent Control

AbstractWe report the temperature dependent NMR of two Diels-Alder adducts of furan: one formed with maleic anhydride and the other with N-methylmaleimide. These adducts are the products of so-called ‘click’ reactions, widely valued for providing simple, reliable, and robust reactivity. Under our experimental conditions, these adducts undergo a retro Diels-Alder reaction and we use our temperature dependent NMR to determine the rates of these reactions at multiple temperatures—ultimately providing estimates of the activation parameters for the reversion. We repeat these measurements in three solvents. We find that, in all solvents, the barrier to reversion is larger for the adduct formed with N-methylmaleimide. The barrier to reversion for this adduct is relatively insensitive to changes in solvent while the adduct formed with maleic anhydride responds more strongly to changes in solvent polarity. The differences in reaction barrier and solvent dependence arises because the adduct formed with N-methylmalemide is more stable—leading to a larger barrier to reversion—while the adduct formed with maleic anhydride experiences a larger change in dipole during the reaction—leading to a larger solvent dependence.

Angucyclinones Related to Ochromycinone. IV. The Structures and Reactions of Unusual Diels-Alder Adducts Formed from Maleic Anhydride and Racemic 5,5-Dimethyl-3-vinylcyclohex-2-en-1-ol

2000 ◽  
Vol 53 (5) ◽  
pp. 403 ◽  
Author(s):  
Craig Brinkworth ◽  
Tomas Rozek ◽  
John H. Bowie ◽  
Brian W. Skelton ◽  
Allan H. White
Keyword(s):  
Carboxylic Acid ◽  
Maleic Anhydride ◽  
Anticancer Activity ◽  
Alder Reaction ◽  
Major Product ◽  
Diels Alder ◽  
Epoxide Ring ◽  
X Ray ◽  
Osmium Tetraoxide ◽  
Diels Alder Reaction

The Diels–Alder reaction between maleic anhydride and racemic 5,5-dimethyl-3-vinylcyclohex-2-en-1-ol gives two racemic diastereomers, the major product (2a,S,3R,8aS,8bR)-7,7-dimethyl-2-oxo-2a,3,4,6,7,8,8a,8b-octahydro-2H-benzo[cd]isobenzofuran-3-carboxylic acid (63% yield), and the minor product (2aR,3S,8aS,8bS)-7,7-dimethyl-2-oxo-2a,3,4,6,7,8,8a,8b-octahydro-2H-benzo[cd]isobenzofuran-3-carboxylic acid (9%). Epoxidation of the major product gives racemic (1aS,3R,3aS,5aR,8aS,8bR)-7,7-dimethyl-4 oxoperhydro-benzo[cd]oxireno[2,3-e]isobenzofuran-3-carboxylic acid in 81% yield, while opening of the epoxide ring gave the trans diol (2aS,3R,5S,5aR,8aR,8bR)-5,5a-dihydroxy-7,7-dimethyl-2-oxoperhydrobenzo[cd]isobenzofuran-3-carboxylic acid in 58% yield. Treatment of the major Diels–Alder product with osmium tetraoxide gave the cis diol (2aS,3R,5S,5aR,8aS,8bR)-5,5a-dihydroxy-7,7-dimethyl-2-oxoperhydrobenzo[cd]isobenzofuran-3-carboxylic acid in 86% yield. The structures of four products were confirmed by X-ray and n.m.r. methods. None of the products exhibit anticancer activity.

Synthesis of Chiral Polyfunctionalised Cyclopentanes from the Diels–Alder Adduct of Furan and Maleic Anhydride

2000 ◽  
Vol 2000 (4) ◽  
pp. 176-178 ◽  
Author(s):  
Richard T. Brown ◽  
Simon B. Jameson ◽  
Dehimi Ouali ◽  
Peter I. Tattersall
Keyword(s):  
Maleic Anhydride ◽  
Enantiomeric Excess ◽  
Diels Alder ◽  
Pig Liver ◽  
Pig Liver Esterase ◽  
Liver Esterase ◽  
Derivatives Of ◽  
Alder Adduct

Chiral polyfunctionalised cyclopentanes have been readily obtained in ~65% enantiomeric excess via a stereo-specific Wagner–Meerwein rearrangement induced by bromination of derivatives of the exo-cis Diels–Alder adduct of furan and maleic anhydride, combined with desymmetrisation of a meso intermediate by pig liver esterase.

Interventional Thermal Injury of the Arterial Wall: Unfolding of von Willebrand Factor and Its Increased Binding to Collagen after 55° C Heating

1996 ◽  
Vol 75 (03) ◽  
pp. 515-519 ◽  
Author(s):  
Mark J Post ◽  
Anke N de Graaf-Bos ◽  
George Posthuma ◽  
Philip G de Groot ◽  
Jan J Sixma ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Conformational Changes ◽  
Arterial Wall ◽  
Platelet Adhesion ◽  
Type I ◽  
Temperature Dependent ◽  
Collagen Types ◽  
Electron Microscopic ◽  
Von Willebrand ◽  
Willebrand Factor

Summary Purpose. Thermal angioplasty alters the thrombogenicity of the arterial wall. In previous studies, platelet adhesion was found to increase after heating human subendothelium to 55° C and decrease after heating to 90° C. In the present electron microscopic study, the mechanism of this temperature-dependent platelet adhesion to the heated arterial wall is elucidated by investigating temperature-dependent conformational changes of von Willebrand factor (vWF) and collagen types I and III and the binding of vWF to heated collagen. Methods. Purified vWF and/or collagen was applied to electron microscopic grids and heated by floating on a salt-solution of 37° C, 55° C or 90° C for 15 s. After incubation with a polyclonal antibody against vWF and incubation with protein A/gold, the grids were examined by electron microscopy. Results. At 37° C, vWF was coiled. At 55° C, vWF unfolded, whereas heating at 90° C caused a reduction in antigenicity. Collagen fibers heated to 37° C were 60.3 ± 3.1 nm wide. Heating to 55° C resulted in the unwinding of the fibers, increasing the width to 87.5 ± 8.2 nm (p < 0.01). Heating to 90° C resulted in denatured fibers with an enlarged width of 85.1 ± 6.1 nm (p < 0.05). Heating of collagen to 55° C resulted in an increased vWF binding as compared to collagen heated to 37° C or to 90° C. Incubation of collagen with vWF, prior to heating, resulted in a vWF binding after heating to 55° C that was similar to the 37° C binding and a decreased binding after 90° C. Conclusions. After 55° C heating, the von Willebrand factor molecule unfolds and collagen types I and III exhibit an increased adhesiveness for von Willebrand factor. Heating to 90° C denatures von Willebrand factor and collagen. The conformation changes of von Willebrand factor and its altered binding to collagen type I and III may explain the increased and decreased platelet adhesion to subendothelium after 55° C and 90° C heating, respectively.

Asymmetric Diels-Alder reactions with a chiral maleic anhydride analog, 5-(1-menthyloxy)-2(5H)-furanone

1988 ◽  
Vol 53 (5) ◽  
pp. 1125-1127 ◽  
Author(s):  
Ben L. Feringa ◽  
Johannes C. De Jong
Keyword(s):  
Maleic Anhydride ◽  
Diels Alder

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

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