The trifluoromethoxy group:- a long-range electron-withdrawing substituent
Judged by its capacity to promote a hydrogen/metal permutation at an ortho position, the trifluoromethoxy group is superior to both the methoxy and trifluoromethyl groups. Moreover, like CF3 and unlike OCH3, OCF3 exerts a long-range effect that still considerably lowers the basicity of arylmetal compds. when located in a more remote meta or even para position. As a consequence, 4-(trifluoromethoxy)anisole is deprotonated by sec-butyllithium mainly, and by tert-butyllithium exclusively, at a position adjacent to the OCH3 group rather than next to the strongly electron-withdrawing CF3O group. 1,3-Benzodioxole undergoes ortho lithiation only six times faster than anisole, whereas 2,2-difluoro-1,3-benzodioxole reacts about 5000 times faster, as evidenced by competition expts. The structure and distance dependence of substituent effects can be rationalized by assuming superposing s- and p-polarizing interactions. [on SciFinder (R)]
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Castagnetti, E., & Schlosser, M. (2002). The trifluoromethoxy group:- a long-range electron-withdrawing substituent. Chemistry - A European Journal, 8(4), 799–804. https://doi.org/10.1002/1521-3765(20020215)8:4<799::AID-CHEM799>3.0.CO;2-6
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WOS:000174100000006
2002
8
4
799
804
CAN 137:5886 22-12 Physical Organic Chemistry Institut de Chimie Organique Ecole Polytechnique Federale de Lausanne,Lausanne,Switz. Journal 0947-6539 written in English. 274-09-9 (1,3-Benzodioxole); 710-18-9 (4-(Trifluoromethoxy)anisole); 1583-59-1 (1,3-Benzodioxole, 2,2-difluoro-); 2216-69-5 (1-Methoxynaphthalene); 403646-52-6 (Naphthalene, 1-(trifluoromethoxy)-) Role: CPS (Chemical process), PEP (Physical, engineering or chemical process), PRP (Properties), RCT (Reactant), PROC (Process), RACT (Reactant or reagent) (trifluoromethoxy group as long-range electron-withdrawing substituent); 142738-94-1P (Benzene, 1-methoxy-3-(Trifluoromethoxy)-); 261952-22-1P (Benzene, 1-methoxy-2-(Trifluoromethoxy)-) Role: CPS (Chemical process), PEP (Physical, engineering or chemical process), PRP (Properties), RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), PROC (Process), RACT (Reactant or reagent) (trifluoromethoxy group as long-range electron-withdrawing substituent); 827-99-6 (Phenol, 3-(trifluoromethoxy)-); 32858-93-8 (Phenol, 2-(trifluoromethoxy)-) Role: RCT (Reactant), RACT (Reactant or reagent) (trifluoromethoxy group as long-range electron-withdrawing substituent); 594-19-4 (tert-Butyllithium); 598-30-1 (sec-Butyllithium) Role: RGT (Reagent), RACT (Reactant or reagent) (trifluoromethoxy group as long-range electron-withdrawing substituent); 883-21-6P (2-Naphthoic acid, 1-methoxy); 5768-39-8P (1,3-Benzodioxole-4-carboxylic acid); 191604-88-3P (Benzoic acid, 2-methoxy-5-(trifluoromethoxy)-); 433330-69-9P; 433330-70-2P; 433330-71-3P; 433330-72-4P; 433330-73-5P Role: SPN (Synthetic preparation), PREP (Preparation) (trifluoromethoxy group as long-range electron-withdrawing substituent)
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