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  4. Relay propagation of crowding: the trifluoromethyl group as both an emitter and transmitter of steric pressure
 
research article

Relay propagation of crowding: the trifluoromethyl group as both an emitter and transmitter of steric pressure

Schlosser, Manfred  
•
Cottet, Fabrice  
•
Heiss, Christophe  
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2006
European Journal of Organic Chemistry

Whereas lithium 2,2,6,6-tetramethylpiperidide (LITMP) abstrs. a proton exclusively from the 4-position of 3-bromobenzotrifluoride, the same base attacks selectively the 2-position when employed in the presence of N,N,N',N'',N''-pentamethyldiethylenetriamine and potassium tert-butoxide ("Faigl mix"). 1-Bromo-3,5-bis(trifluoromethyl)benzene also undergoes metalation at the 2-position but [2-bromo-4-(trifluoromethyl)phenyl]silane does not react at all, evidently locked up by a C-SiR3/C-Br buttressing effect. 2-Bromo-4-(trifluoromethyl)pyridine, aza-analogous to the parent model arene 3-bromobenzotrifluoride, and both the benzo-azaanalogous 2-bromo-4-(trifluoromethyl)quinoline and its regioinverted isomer 4-bromo-2-(trifluoromethyl)quinoline are again readily deprotonated at the Br- and CF3-flanked positions. However, the buttressing caused by the introduction of a methoxy group at the peri-(5-)position impedes the deprotonation of either bromo(trifluoromethyl)quinoline. Compared with methoxy, a peri-Me substituent (to be assimilated to an ortho-tert-Bu substituent) exerts a smaller buttressing effect. Although 4-bromo-5,7-dimethoxy-4-(trifluoromethyl)quinoline proves to be again totally inert towards bases, 4-bromo-5,7-dimethyl-4-(trifluoromethyl)quinoline can be lithiated at the 3-position. Obviously, methoxy is more powerful as an emitter of steric pressure than Me is and bromine is superior to trifluoromethyl as a transmitter of steric pressure. [on SciFinder (R)]

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Type
research article
DOI
10.1002/ejoc.200500728
Web of Science ID

WOS:000235349000020

Author(s)
Schlosser, Manfred  
Cottet, Fabrice  
Heiss, Christophe  
Lefebvre, Olivier
Marull, Marc  
Masson, Eric  
Scopelliti, Rosario  
Date Issued

2006

Published in
European Journal of Organic Chemistry
Issue

3

Start page

729

End page

734

Note

22 Physical Organic Chemistry Institute of Chemical Sciences and Engineering,Ecole Polytechnique Federale,Lausanne,Switz. Journal 1434-193X written in English.

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LSCO  
Available on Infoscience
March 3, 2006
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/227052
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