Origin of the preference for the chair conformation in the Cope rearrangement. Effect of phenyl substituents on the chair and boat transition states

1992 ◽  
Vol 114 (7) ◽  
pp. 2635-2643 ◽  
Author(s):  
K. J. Shea ◽  
G. J. Stoddard ◽  
W. P. England ◽  
C. D. Haffner
Keyword(s):  
Transition States ◽  
Chair Conformation ◽  
Cope Rearrangement ◽  
Rearrangement Effect

[3,3] Sigmatropic Rearrangement of Some Fluorinated 1,5-Hexadienes

2002 ◽  
Vol 67 (10) ◽  
pp. 1517-1532 ◽  
Author(s):  
William R. Dolbier ◽  
Keith W. Palmer ◽  
Feng Tian ◽  
Piotr Fiedorow ◽  
Andrzej Zaganiaczyk ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Transition States ◽  
Activation Parameters ◽  
Sigmatropic Rearrangement ◽  
Semiempirical Methods ◽  
Cope Rearrangement ◽  
Computational Studies ◽  
Stepwise Mechanism ◽  
Radical Intermediates

Fluorine atoms incorporated into 1,5-hexadiene molecule should influence the kinetic as well as the thermodynamic parameters of [3,3] sigmatropic rearrangement (Cope rearrangement). Within few decades is has been documented that this transformation proceeds in a concerted manner, rather than stepwise with some radical intermediates involved. Few new terminally fluorinated 1,5-hexadienes (compounds 3, 5A, 7, 9 and 5B) have been synthesized. The activation parameters of rearrangement have been determined and compared with those known for hydrocarbon analogues. While systems developing chair-like transition states (compounds 3 and 5) showed close similarity with hydrocarbon analogues (compound 1), those developing boat-like transition states (compounds 7, 9 and 5B) may proceed through radical stepwise mechanism. Computational studies of the transition states were carried out, showing that only ab initio methods (MP2 and especially DFT) can give approximate correlation with experimental data, whereas in the case of hydrocarbon analogues even simple semiempirical methods (AM1) were reliable enough to reproduce experimental results.

ChemInform Abstract: Chair and Boat Transition States for the Cope Rearrangement. A CASSCF Study.

ChemInform ◽  
1988 ◽  
Vol 19 (42) ◽  
Author(s):  
K. MOROKUMA ◽  
W. T. BORDEN ◽  
D. A. HROVAT
Keyword(s):  
Transition States ◽  
Cope Rearrangement
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