Rate enhancing and rate retarding effects of methoxy substituents on arene metalation

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)]


Published in:
Tetrahedron Letters, 40, 50, 8797-8800
Year:
1999
Keywords:
Note:
CAN 132:92998
22-12
Physical Organic Chemistry
Institut de Chimie organique de l'Universite (BCh),Lausanne,Switz.
Journal
0040-4039
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)
Laboratories:




 Record created 2006-03-03, last modified 2018-01-27


Rate this document:

Rate this document:
1
2
3
 
(Not yet reviewed)