The effect of an alkoxy group on the kinetic and thermodynamic acidity of benzene and toluene
2-, 3- And 4-Methoxytoluene can be selectively metalated at an O-adjacent ortho position when butylithium or tert-butyllithium in the presence of sodium (potassium) tert-butoxide or N,N,N',N",N"-pentamethyldiethylenetriamine are employed as reagents. In contrast, lithium diisopropylamide or lithium 2,2,6,6-tetramethylpiperidide deprotonate the benzylic a-position of 2- and 3-methoxytoluene exclusively and of 4-methoxytoluene preferentially. These relative reactivities can be rationalized by an interplay of transition state stabilizing and destabilizing forces (dipole matching and metal coordination vs. lone pair repulsion). [on SciFinder (R)]
1998
54
12
2763
2770
CAN 128:243708
22-12
Physical Organic Chemistry
Institut de Chimie organique de l'Universite,Lausanne-Dorigny,Switz.
Journal
written in English.
1657-55-2P (1,2-Bis(4-methoxyphenyl)ethane) Role: BYP (Byproduct), PREP (Preparation) (The effect of an alkoxy group on the kinetic and thermodn. acidity of benzene and toluene); 100-84-5 (3-Methoxytoluene); 104-93-8 (4-Methoxytoluene); 578-58-5 (2-Methoxytoluene); 74260-40-5 (Tributyl(4-methoxybenzyl)tin) Role: PEP (Physical, engineering or chemical process), RCT (Reactant), PROC (Process), RACT (Reactant or reagent) (The effect of an alkoxy group on the kinetic and thermodn. acidity of benzene and toluene); 98-51-1 (4-tert-Butyltoluene) Role: PRP (Properties), RCT (Reactant), RACT (Reactant or reagent) (The effect of an alkoxy group on the kinetic and thermodn. acidity of benzene and toluene); 93-25-4P ((2-Methoxyphenyl)acetic acid); 104-01-8P ((4-Methoxyphenyl)acetic acid); 704-45-0P; 1798-09-0P ((3-Methoxyphenyl)acetic acid); 5406-18-8P; 18927-05-4P; 23786-14-3P; 25045-36-7P; 26507-91-5P; 27798-60-3P; 52239-62-0P; 63113-79-1P; 81245-24-1P Role: SPN (Synthetic preparation), PREP (Preparation) (The effect of an alkoxy group on the kinetic and thermodn. acidity of benzene and toluene); 109-72-8 (Butyllithium); 594-19-4 (tert-Butyllithium); 865-47-4; 865-48-5 (Sodium tert-butoxide); 917-54-4 (Methyllithium); 3030-47-5 (N,N,N',N",N"-Pentamethyldiethylenetriamine); 4111-54-0 (LDA); 38227-87-1 (Lithium 2,2,6,6-tetramethylpiperidide) Role: PEP (Physical, engineering or chemical process), RCT (Reactant), PROC (Process), RACT (Reactant or reagent) (metalation agent; The effect of an alkoxy group on the kinetic and thermodn. acidity of benzene and toluene)
REVIEWED
EPFL