Substituent Effects in the Thermal Isomerization of 1,2-Dicarbonyl Derivatives of 3,6-Bridged 1,2,3,6-Tetrahydropyridazines

1975 ◽  
Vol 53 (4) ◽  
pp. 535-541 ◽  
Author(s):  
John A. Campbell ◽  
Ian Harris ◽  
Donald Mackay ◽  
Timothy D. Sauer
Keyword(s):  
Substituent Effects ◽  
Thermal Isomerization ◽  
Diels Alder ◽  
Effect Of Substituents ◽  
Rotation Rates ◽  
Derivatives Of ◽  
Cyclic Intermediate

The Diels–Alder adducts of cyclopentadiene and azodiacyls or azodiaroyls isomerize to 1,3,4-oxadiazines at rates which show a trend qualitatively related to the rotation rates of the corresponding N,N-dimethylamides. The isomerizations probably occur by a cyclic concerted mechanism.The ring substituents in the adducts of 1,4-dimethyl-2,3-diphenylcyclopentadiene and azodibenzoyl or azodiacetyl accelerate the isomerization; the kinetic evidence supports a cyclic intermediate in the reaction in isooctane as solvent but is more consistent with a dipolar intermediate in aqueous ethanol.Some generalizations about the effect of substituents on the isomerization are presented on the basis of these and earlier experiments.

Synthesis and Isomerization of Adducts of Azodicarbonyl Compounds and Cyclopentadiene

1972 ◽  
Vol 50 (3) ◽  
pp. 371-380 ◽  
Author(s):  
J. A. Campbell ◽  
Donald Mackay ◽  
T. D. Sauer
Keyword(s):  
Thermal Isomerization ◽  
Diels Alder ◽  
Derivatives Of

The synthesis of a range of bicyclic Diels–Alder adducts (structures b) of cyclopentadiene with symmetrical and unsymmetrical azodicarbonyl compounds is described. Thermal isomerization of these adducts to the bicyclic 1,3,4-oxadiazines (structures c and d) is especially rapid with bulky acyl groups. In unsymmetrical adducts with acyl groups of markedly different size, the larger group dictates completely the direction of isomerization. Adducts with two different aroyl groups give both isomers.Spectroscopic properties of the adducts, the oxadiazines and the dihydro derivatives of the oxadiazines are described.

Infrared spectra and substituent effects in 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones

1983 ◽  
Vol 48 (2) ◽  
pp. 586-595 ◽  
Author(s):  
Alexander Perjéssy ◽  
Pavol Hrnčiar ◽  
Ján Šraga
Keyword(s):  
Substituent Effects ◽  
Phenyl Group ◽  
Wave Number ◽  
Vibrational Coupling ◽  
Wave Numbers ◽  
Stretching Vibration ◽  
Stretching Vibrations ◽  
The Relationship ◽  
Derivatives Of ◽  
Effect Of Structure

The wave numbers of the fundamental C=O and C=C stretching vibrations, as well as that of the first overtone of C=O stretching vibration of 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones and 1,3-cycloheptanedione were measured in tetrachloromethane and chloroform. The spectral data were correlated with σ+ constants of substituents attached to phenyl group and with wave number shifts of the C=O stretching vibration of substituted acetophenones. The slope of the linear dependence ν vs ν+ of the C=C stretching vibration of the ethylenic group was found to be more than two times higher than that of the analogous correlation of the C=O stretching vibration. Positive values of anharmonicity for asymmetric C=O stretching vibration can be considered as an evidence of the vibrational coupling in a cyclic 1,3-dicarbonyl system similarly, as with derivatives of 1,3-indanedione. The relationship between the wave numbers of the symmetric and asymmetric C=O stretching vibrations indicates that the effect of structure upon both vibrations is symmetric. The vibrational coupling in 1,3-cycloheptanediones and the application of Seth-Paul-Van-Duyse equation is discussed in relation to analogous results obtained for other cyclic 1,3-dicarbonyl compounds.

Nuclear magnetic resonance characterization of the ring conformations of monosubstituted derivatives of 1,3-dioxa-5,6-benzocycloheptene

1983 ◽  
Vol 61 (1) ◽  
pp. 109-115 ◽  
Author(s):  
R. St-Amour ◽  
M. St-Jacques
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Substituent Effects ◽  
Steric Effects ◽  
Slow Exchange ◽  
Conformational Properties ◽  
Derivatives Of ◽  
Ring Conformations ◽  
Twist Boat

The conformational properties of 2-alkyl (Me, Et, i-Pr, and t-Bu) and 2-phenyl derivatives of 1,3-dioxa-5,6-benzocycloheptene (1) were studied by 13C dnmr. Analysis of slow exchange spectra at 100.6 MHz indicates that all derivatives except tert-butyl exist in an equilibrium of chair (major) and twist-boat (minor) conformations. Substituent effects on the position of the equilibrium are rationalized in terms of steric effects.

Effect of Substituents on Photochemical and Biological Properties of 13,15-N-Cycloimide Derivatives of Chlorin p6

2005 ◽  
Vol 31 (5) ◽  
pp. 482-494 ◽  
Author(s):  
A. I. Nazarova ◽  
A. V. Feofanov ◽  
T. A. Karmakova ◽  
G. V. Sharonov ◽  
A. D. Plyutinskaya ◽  
...  
Keyword(s):  
Biological Properties ◽  
Effect Of Substituents ◽  
Derivatives Of ◽  
Chlorin P6
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