ChemInform Abstract: VARIATION OF STERIC EFFECTS IN METAL ION-CATALYZED PROTON TRANSFER. A PROBE OF TRANSITION-STATE STRUCTURE

1984 ◽  
Vol 15 (21) ◽  
Author(s):  
R. KLUGER ◽  
M. K. WONG ◽  
A. K. DODDS
2020 ◽  
Author(s):  
Veejendra Yadav

In comparison to the popular pathway involving proton-transfer via a four-centred cyclic transition state structure, the recently proposed overall lower energy pathway involving proton-transfer via a seven-centred cyclic transition state structure followed by Hofmann elimination for the Me<sub>3</sub>N-catalyzed Morita-Baylis-Hillman reaction is applicable to the DABCO-catalyzed reaction equally well. This finding clearly establishes that the zwitterion at the bridge-head in DABCO is well tolerated. Also, the activation free energy of the rate-limiting aldol reaction under DABCO-catalysis is lower than that under Me<sub>3</sub>N-catalysis, suggesting that DABCO is likely a better catalyst to achieve faster conversion.


2020 ◽  
Author(s):  
Veejendra Yadav

In comparison to the popular pathway involving proton-transfer via a four-centred cyclic transition state structure, the recently proposed overall lower energy pathway involving proton-transfer via a seven-centred cyclic transition state structure followed by Hofmann elimination for the Me<sub>3</sub>N-catalyzed Morita-Baylis-Hillman reaction is applicable to the DABCO-catalyzed reaction equally well. This finding clearly establishes that the zwitterion at the bridge-head in DABCO is well tolerated. Also, the activation free energy of the rate-limiting aldol reaction under DABCO-catalysis is lower than that under Me<sub>3</sub>N-catalysis, suggesting that DABCO is likely a better catalyst to achieve faster conversion.


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