Buttressing Effects on Haloarene Deprotonation: A Merely Kinetic or Also Thermodynamic Phenomenon?
(2,6-Dichlorophenyl)- and (2,6-dibromophenyl)trialkylsilanes undergo hydrogen/metal interconversion preferentially at the 4- rather than 3-position. However, the organometallic species generated by such a "meta metalation" are thermodynamically less stable (i.e., more basic) than those that would result from an ordinary "ortho metalation". This was demonstrated by equilibration expts. based on permutational halogen/metal interconversion. A new buttressing effect can explain the unprecedented regioselectivity. It is supported by X-ray structures that reveal marked deformations of the benzene ring in halophenylsilanes. [on SciFinder (R)]
WOS:000225280200050
2004
6
24
4591
4593
CAN 142:22985
22-12
Physical Organic Chemistry
Institute of Chemical Sciences and Engineering (ISIC),Ecole Polytechnique Federale,Lausanne,Switz.
Journal
written in English.
17989-28-5; 121412-28-0 ((2,4-Dichlorophenyl)lithium); 802984-56-1; 802984-57-2 Role: CPS (Chemical process), FMU (Formation, unclassified), PEP (Physical, engineering or chemical process), RCT (Reactant), FORM (Formation, nonpreparative), PROC (Process), RACT (Reactant or reagent) (buttressing effects on haloarene deprotonation kinetics or thermodn. phenomenon); 19752-55-7 (3,5-Dichloro-1-bromobenzene); 650598-50-8 (4-Triethylsilyl-3,5-dichloro-1-bromobenzene) Role: FMU (Formation, unclassified), FORM (Formation, nonpreparative) (buttressing effects on haloarene deprotonation kinetics or thermodn. phenomenon); 802984-55-0P Role: FMU (Formation, unclassified), PRP (Properties), SPN (Synthetic preparation), FORM (Formation, nonpreparative), PREP (Preparation) (buttressing effects on haloarene deprotonation kinetics or thermodn. phenomenon); 1193-72-2 (1-Bromo-2,4-dichlorobenzene) Role: FMU (Formation, unclassified), RCT (Reactant), FORM (Formation, nonpreparative), RACT (Reactant or reagent) (buttressing effects on haloarene deprotonation kinetics or thermodn. phenomenon); 802984-53-8P; 802984-54-9P Role: PRP (Properties), SPN (Synthetic preparation), PREP (Preparation) (buttressing effects on haloarene deprotonation kinetics or thermodn. phenomenon); 108-18-9 (Diisopropylamine); 3032-81-3; 29898-32-6; 650598-44-0 Role: RCT (Reactant), RACT (Reactant or reagent) (buttressing effects on haloarene deprotonation kinetics or thermodn. phenomenon); 650598-42-8 (3,5-Dibromo-4-triethylsilylbenzoic acid) Role: PRP (Properties) (crystal structure; of 3,5-dibromo-4-triethylsilylbenzoic acid); 650598-41-7 (3,5-Dichloro-4-triethylsilylbenzoic acid) Role: PRP (Properties) (crystal structure; of 3,5-dichloro-4-triethylsilylbenzoic acid)
REVIEWED
EPFL