On the regioselectivity of the condensation of stabilized phosphoylids with 3-substituted phthalic anhydrides

1989 ◽  
Vol 67 (4) ◽  
pp. 569-573 ◽  
Author(s):  
Livain Breau ◽  
Margaret M. Kayser
Keyword(s):  
Oxygen Atom ◽  
Transition State ◽  
Carbonyl Group ◽  
Lewis Base ◽  
Carbonyl Function ◽  
Deficient Phosphorus ◽  
Phthalic Anhydrides

Condensations of stabilized phosphorane 1 with 3-substituted phthalic anhydrides were investigated. The importance of various effects influencing regio- and stereoselectivity of these reactions is discussed. It is proposed that the oxygen atom on the substituents in position 3 can act as a Lewis base toward the electron-deficient phosphorus of the ylid. The resulting complexation stabilizes the transition state for the reaction at the ortho carbonyl group, thus offsetting the usual steric and "push" effects, which favour attack at the meta carbonyl function. Keywords: Wittig condensations, phthalic anhydrides, regioselectivity, stereoselectivity.

On the regioselectivity of Wittig reactions with unsymmetrically substituted succinic anhydrides

1989 ◽  
Vol 67 (9) ◽  
pp. 1401-1410 ◽  
Author(s):  
Margaret M. Kayser ◽  
Livain Breau
Keyword(s):  
Oxygen Atom ◽  
Transition State ◽  
Carbonyl Group ◽  
Wittig Reaction ◽  
Cyclic Anhydrides ◽  
Wittig Reactions ◽  
Deficient Phosphorus

Phosphorane ylids react readily with succinic anhydrides to give enol-lactones. With highly substituted succinic anhydrides, condensations occur at the less substituted carbonyl group, suggesting that the reaction is sterically controlled. This, however, is not the case in monosubstituted anhydrides where effects other than steric become dominant. Condensation of phosphorane 1a with methoxysuccinic anhydride occurs selectively at the carbonyl group adjacent to the substituent. Stabilization of the transition state through complexation between the oxygen atom of the substituent and an electron-deficient phosphorus of the ylid is proposed. Keywords: cyclic anhydrides, Wittig reaction, regioselectivity, stabilized ylid.

Notizen: Oxygen Incorporation in Cleavage of 18-Labeled 13-HydroperoxylinoIeyl Alcohol into 12-Hydroxy- (3Z)-dodecenal in Tea Chloroplasts

1986 ◽  
Vol 41 (3) ◽  
pp. 359-362 ◽  
Author(s):  
Akikazu Hatanaka ◽  
Tadahiko Kajiwara ◽  
Jiro Sekiya ◽  
Hiromitsu Toyota
Keyword(s):  
Oxygen Atom ◽  
Carbonyl Group ◽  
Oxygen Incorporation

The oxygen atom in the hydroperoxy group of 13-hydroperoxylinoleyl alcohol was primarily incorporated into the carbonyl group of 12-hydroxy-(3Z)-dodecenal but scarcely into n-hexanal during the incubation with tea chloroplasts.

INFRARED SPECTRA OF 2,6-DIMETHYL-4-PYRONE COMPLEXES

1961 ◽  
Vol 39 (6) ◽  
pp. 1184-1189 ◽  
Author(s):  
Denys Cook
Keyword(s):  
Complex Formation ◽  
Oxygen Atom ◽  
Carbonyl Group ◽  
Lewis Acid ◽  
Frequency Band ◽  
Infrared Spectra ◽  
Donor Site ◽  
Carbonyl Oxygen ◽  
Acid Strength ◽  
Group A

The infrared spectra of 2,6-dimethyl-4-pyrone in solution, and in complexes with HgCl2, ZnCl2, BF3, SbCl5, and HBr have been recorded. A band at 1639 cm−1 in the free pyrone moves to progressively lower frequencies in the complexes as the Lewis acid strength increases, identifying this band as the carbonyl stretching frequency and the donor site as the carbonyl group. A higher-frequency band, at 1678 cm−1 in the free pyrone, moves to lower frequency on complex formation, but to a much smaller extent, and is to be identified with a stretching mode of the ring. The site of protonation in 2,6-dimethyl-4-pyrone salts has been unequivocally shown to be the carbonyl oxygen atom.

γ-Silylated α,β-unsaturated amides — Preparation by [1,5]-sigmatropic rearrangement and use as masked dienolate equivalents in carbonyl condensations

2009 ◽  
Vol 87 (6) ◽  
pp. 745-759 ◽  
Author(s):  
James R. Green ◽  
Babajide I. Alo ◽  
Marek Majewski ◽  
Victor Snieckus
Keyword(s):  
Oxygen Atom ◽  
Transition State ◽  
Condensation Product ◽  
Aromatic Aldehydes ◽  
Sigmatropic Rearrangement ◽  
Fluoride Ion ◽  
Bidentate Coordination ◽  
State Models

The reaction of lithium dienolates derived from N,N-dialkylsenecioamides (1a–1c) with triorganosilyl electrophiles occurs initially at the oxygen atom predominantly, and is followed by an O → C silicon migration to afford the γ-silylated senecioamides (4a–4h). The γ-silylated senecioamide Z-4a undergoes fluoride-ion-mediated condensations with aromatic aldehydes to give kinetic α-(6) and thermodynamic γ-(5) condensation product patterns comparable to lithium dienolates. The TiCl4-mediated reactions with aldehydes gives α-products (6) in a highly syn-selective manner. Possible transition-state models for the syn-selective condensations are discussed and a chair-like transition state featuring bidentate coordination to titanium (11) is proposed.

Ab initio calculations of the oxygen atom NMR shielding in the carbonyl group

1993 ◽  
Vol 203 (4) ◽  
pp. 404-408 ◽  
Author(s):  
Andrzej Barszczewicz ◽  
Michał Jaszuński ◽  
Karol Jackowski
Keyword(s):  
Oxygen Atom ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Carbonyl Group

scholarly journals Synthesis and Spectral Studies of Novel Palladium (O) Complex with Ciprofloxacin Antibiotic

2018 ◽  
Vol 7 (4.36) ◽  
pp. 722
Author(s):  
N. S. Majeed ◽  
I. K. Kareem ◽  
N. N.A. Jafar
Keyword(s):  
Oxygen Atom ◽  
Carbonyl Group ◽  
1H Nmr ◽  
13C Nmr ◽  
Molar Conductance ◽  
Spectral Studies ◽  
Neutral Ligand ◽  
Tetrahedral Structure ◽  
Ft Ir ◽  
Prepared Complex

New complex of Palladium (0) with ciprofloxacin has been synthesized, The complex was portrayed by different physico - substance systems like essential examination, m.pt. , TLC, molar conductance estimation, attractive helplessness,13C- NMR, 1H-NMR and FT-IR. According to the results obtained, tetrahedral structure suggested for the prepared complex. The neutral ligand act in a Didentate mode, binding through oxygen atom of carbonyl group in pyridonering and oxygen atom of carboxyl ate group.  

Pyrolysis of Aryl Azides. XIII. Conformational Effects on the Ability of Carbonyl as a Neighbouring Group

1996 ◽  
Vol 49 (11) ◽  
pp. 1197 ◽  
Author(s):  
LK Dyall ◽  
JA Ferguson ◽  
TB Jarman
Keyword(s):  
Transition State ◽  
Carbonyl Group ◽  
Electronic Effects ◽  
Aryl Azides ◽  
Conformational Effects ◽  
Acetyl Group ◽  
Previous Claim

Our previous claim, that locking an ortho carbonyl group into a favourable conformation causes very large increases in the rate of thermolysis of aryl azides , has been reexamined. In 8-azido-5-methoxy-1-tetralone the rate advantage over an azide with a rotatable ortho acetyl group is estimated to be only 18-fold. Nevertheless, this factor is large enough to invalidate attempts to explain relative neighbouring group abilities on simple electronic effects alone. The very large rate increases we reported previously for 1-azidoacridin-g(10H)-one and 1-azidoanthracene-9,10-dione are partly due to favourable retention of conjugation in the transition state.

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