The rate retarding effect of alkyl groups on arene metalation quantified
Metalation/trapping sequences applied to relatively inert, tert-alkyl substituted arenes tend to give poor yields unless the reagent is used in high concns. Under optimized conditions, even 1,4-bis(tert-butyl)benzene, 1,1,3,3-tetramethylindane and 1,1,2,2,3,3-hexamethylindane can be smoothly converted into derivs. Competition expts. enable the quant. assessment of tert-alkyl substituent effects on the metalation rates at arom. ortho, meta and para positions. Unlike alkyl groups, hetero elements generally accelerate metalation reactions. 1,1,3,3-Tetramethyl-1,3-dihydroisobenzofuran undergoes the H/metal exchange 3-6 times faster than the indanes mentioned above, the reaction occurring at both the 5- and at the 4-position. [on SciFinder (R)]
2000
41
5
667
670
CAN 132:237116
29-2
Organometallic and Organometalloidal Compounds
Section de Chimie (BCh), Universite,Lausanne,Switz.
Journal
written in English.
71-43-2 (Benzene); 98-06-6 (tert-Butylbenzene); 1012-72-2; 1014-60-4; 4834-33-7; 91324-94-6; 113710-83-1 Role: PEP (Physical, engineering or chemical process), PRP (Properties), RCT (Reactant), PROC (Process), RACT (Reactant or reagent) (rate retarding effect of alkyl groups on arene metalation quantified); 124-38-9 (Carbon dioxide) Role: RCT (Reactant), RACT (Reactant or reagent) (rate retarding effect of alkyl groups on arene metalation quantified); 14034-95-8P; 100971-92-4P; 146271-67-2P; 261788-75-4P; 261788-76-5P Role: SPN (Synthetic preparation), PREP (Preparation) (rate retarding effect of alkyl groups on arene metalation quantified); 109-72-8; 865-47-4 Role: PEP (Physical, engineering or chemical process), PRP (Properties), RCT (Reactant), PROC (Process), RACT (Reactant or reagent) (superbase; rate retarding effect of alkyl groups on arene metalation quantified)
REVIEWED
EPFL