Competition expts. have been performed to det. the rates, relative to benzene, with which anisole, the three dimethoxybenzenes and the three trimethoxybenzenes are deprotonated by sec-butyllithium. Only the first substituent (anisole relative to benzene) has a strong effect (krelf 2800); the second one accelerates moderately at best (1,3-dimethoxybenzene relative to anisole: krelf 12). Methoxy groups being located para with respect to the metalation site or occupying a vicinal position to another methoxy substituent diminish the reactivity by up to two powers of ten (relative to anisole). These surprising findings are without precedence. [on SciFinder (R)]
Titre
Rate enhancing and rate retarding effects of methoxy substituents on arene metalation
Publié dans
Tetrahedron Letters
Volume
40
Numéro
50
Pages
8797-8800
Date
1999
ISSN
0040-4039
Note
CAN 132:92998
22-12
Physical Organic Chemistry
Institut de Chimie organique de l'Universite (BCh),Lausanne,Switz.
Journal
written in English.
71-43-2 (Benzene); 91-16-7 (Catechol dimethyl ether); 100-66-3 (Anisole); 135-77-3 (Hydroxyhydroquinone trimethyl ether); 150-78-7 (Hydroquinone dimethyl ether); 151-10-0 (Resorcinol dimethyl ether); 621-23-8; 634-36-6 (Pyrogallol trimethyl ether) Role: PRP (Properties), RCT (Reactant), RACT (Reactant or reagent) (rate enhancing and rate retarding effects of methoxy substituents on arene metalation)
Date de création de la notice
2006-03-03