Eistert's Methyl Enol Ethers of Acetylacetone

1971 ◽  
Vol 49 (16) ◽  
pp. 2672-2675 ◽  
Author(s):  
Dennis V. C. Awang
Keyword(s):  
Carbonyl Oxygen ◽  
Enol Ether ◽  
Trans Conformation ◽  
Enol Ethers ◽  
Solvent Shift ◽  
Acid Catalyzed ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects ◽  
Configuration And Conformation ◽  
Shift Data

The configuration and conformation of the two isomeric methyl enol ethers of acetylacetone (1) have been unequivocally demonstrated. The n.m.r. solvent shift data and observation of nuclear Overhauser effects support an s-cis conformation for the more stable isomer 2 bearing acetyl trans to methoxyl while indicating an s-trans conformation for the less stable enol ether 3 having acetyl cis to methoxyl. The facile acid-catalyzed isomerization of 3 to 2 apparently proceeds by reversible protonation of carbonyl oxygen since no deuterium incorporation is observed when the isomerization is performed in acetic acid-d4.

Preferred conformations of enol ethers in solution: Detection of an equilibrium by kinetic nuclear overhauser effects

1981 ◽  
Vol 22 (40) ◽  
pp. 4029-4032 ◽  
Author(s):  
John D Mersh ◽  
Jeramy KM Sanders
Keyword(s):  
Enol Ethers ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects

scholarly journals NMR solution conformation of heparin-derived tetrasaccharide

1996 ◽  
Vol 318 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Dmitri MIKHAILOV ◽  
Kevin H. MAYO ◽  
Ioncho R. VLAHOV ◽  
Toshihiko TOIDA ◽  
Azra PERVIN ◽  
...  
Keyword(s):  
Chair Conformation ◽  
Coupling Constants ◽  
Solution Conformation ◽  
1H And 13C Nmr ◽  
Small Deviations ◽  
J Coupling Constants ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects ◽  
Dynamics Simulations ◽  
Ring Conformations

The solution conformation of the homogeneous, heparin-derived tetrasaccharide ΔUA2S(1 → 4)-α-d-GlcNpS6S(1 → 4)-α-l-IdoAp2S(1 → 4)-α-d-GlcNpS6S (residues A, B, C and D respectively, where IdoA is iduronic acid) has been investigated by using 1H- and 13C-NMR. Ring conformations have been defined by J-coupling constants and inter-proton nuclear Overhauser effects (NOEs), and the orientation of one ring with respect to the other has been defined by inter-ring NOEs. NOE-based conformational modelling has been done by using the iterative relaxation matrix approach (IRMA), restrained molecular dynamics simulations and energy minimization to refine structures and to distinguish between minor structural differences and equilibria between various ring forms. Both glucosamine residues B and D are in the 4C1 chair conformation. The 6-O-sulphate group is oriented in the gauche–trans configuration in the D ring, whereas in the B ring the gauche–gauche rotomer predominates. Uronate (A) and iduronate (C) residues are mostly represented by 1H2 and 2S0 twisted boat forms, respectively, with small deviations in expected coupling constants and NOEs suggesting minor contributions from other A and C ring conformations.

The photoaddition of 1,3-diketonatoboron difluorides with benzene derivatives

1991 ◽  
Vol 69 (3) ◽  
pp. 423-431 ◽  
Author(s):  
Yuan L. Chow ◽  
Xinxin Ouyang
Keyword(s):  
Crystallographic Analysis ◽  
Secondary Oxidation ◽  
Enol Ethers ◽  
X Ray ◽  
Thermal Reactions ◽  
Secondary Reactions ◽  
Enol Acetates ◽  
Orthogonal Orientation ◽  
Acid Catalyzed ◽  
Boron Difluoride

The boron difluoride complexes of 2-acetylcyclohexanone, 2-acetylcyclopentanone, and acetylacetone (abbreviated as ACHBF2, ACPBF2, and AABF2) were irradiated in the presence of benzene to give the 1:1 adducts as the primary photoadducts; for certain BF2 complexes, toluene, chlorobenzene, benzonitrile, and methyl benzoate were also used as substrates. The 1,5-diketone photoadducts were assumed to form by a [2+2] photocycloaddition followed by cyclobutane opening and hydrolysis to give 1,2 adducts. They undergo a variety of secondary thermal reactions, probably acid catalyzed, to give enol ethers, enol acetates, acetophenones, and ketonylacetophenones. The efficiency of these secondary reactions determines the final products. Photoaddition with a monosubstituted benzene preferentially occurs at the 3,4 bond without regioselectivity. Under oxygen, ACHBF2 photolytically reacts with benzene to give a secondary oxidation product of a 10-membered cyclic alkylphe-none, which is proven by X-ray crystallographic analysis to have the benzene ring and carbonyl group in orthogonal orientation. It is shown that the singlet excited state ACHBF2 initiates the photoaddition, probably through the formation of the benzene exciplex, which could be detected by its emission. While the Stern–Volmer rates are small, the quantum yield of photoaddition products is as high as 0.12–0.19 under limiting conditions. Key words: [2+2] photocycloaddition, non-planar alkanophenone, macrocyclic alkanophenone, boron difluoride complexes, photoaddition to benzenes.

scholarly journals Asymmetric Synthesis of Cyclic Hydroxy Ketones Derived from Enol Ethers via Sharpless Asymmetric Dihydroxylation. A Study in the Correlation of the Enol Ether Chain Length and Enantioselectivity.

ChemInform ◽  
2004 ◽  
Vol 35 (9) ◽  
Author(s):  
Benjamin F. Marcune ◽  
Sandor Karady ◽  
Paul J. Reider ◽  
Ross A. Miller ◽  
Mirlinda Biba ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Chain Length ◽  
Enol Ether ◽  
Enol Ethers ◽  
Asymmetric Dihydroxylation ◽  
Hydroxy Ketones

Bronsted acid-catalyzed rapid enol-ether formation of 2-hydroxyindole-3-carboxaldehydes

2013 ◽  
Vol 17 (4) ◽  
pp. 827-834 ◽  
Author(s):  
Darian Blanchard ◽  
T. Stanley Cameron ◽  
Mukund Jha
Keyword(s):  
Bronsted Acid ◽  
Brønsted Acid ◽  
Enol Ether ◽  
Brönsted Acid ◽  
Acid Catalyzed

Carbon-carbon bond formation in reactions of PhIO.cntdot.HBF4-silyl enol ether adduct with alkenes or silyl enol ethers

1989 ◽  
Vol 54 (11) ◽  
pp. 2605-2608 ◽  
Author(s):  
V. V. Zhdankin ◽  
M. Mullikin ◽  
Rik Tykwinski ◽  
Bruce Berglund ◽  
Ronald Caple ◽  
...  
Keyword(s):  
Bond Formation ◽  
Enol Ether ◽  
Enol Ethers ◽  
Carbon Bond ◽  
Silyl Enol Ethers ◽  
Carbon Carbon Bond ◽  
Silyl Enol Ether

scholarly journals Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

2010 ◽  
Vol 6 ◽  
Author(s):  
Fabian Pfrengle ◽  
Hans-Ulrich Reissig
Keyword(s):  
Lewis Acid ◽  
Functional Group ◽  
Tricarboxylic Acid ◽  
Membered Ring ◽  
Enol Ether ◽  
Enol Ethers ◽  
Acidic Conditions ◽  
Hydroxylamine Derivatives

A stereodivergent synthesis of enantiopure 3,6-dihydro-2H-pyrans is presented. The addition of lithiated enol ethers to carbohydrate-derived nitrones afforded syn- or anti-configured hydroxylamine derivatives 4a–d that were cyclized under Lewis acidic conditions to yield functionalized dihydropyrans cis- or trans-5a–d containing an enol ether moiety. This functional group was employed for a variety of subsequent reactions such as dihydroxylation or bromination. Bicyclic enol ether 19 was oxidatively cleaved to provide the highly functionalized ten-membered ring lactone 20. The synthesized enantiopure aminopyrans 24, 26, 28 and 30 can be regarded as carbohydrate mimetics. Trimeric versions of 24 and 28 were constructed via their attachment to a tricarboxylic acid core.

Structure assignment of some 3,4′-diquinolinyl sulfides studied by Nuclear Overhauser Effects, X-ray analysis and reactions with sodium methoxide

2010 ◽  
Vol 109 (10) ◽  
pp. 509-514 ◽  
Author(s):  
Stanislaw Boryczka ◽  
Andrzej Maślankiewicz ◽  
Miroslaw Wyszomirski ◽  
Teresa Borowiak ◽  
Maciej Kubicki
Keyword(s):  
Sodium Methoxide ◽  
X Ray ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects ◽  
Structure Assignment
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