Dimetalation: the acidity of monometalated arenes towards superbasic reagents
Twofold H/metal interconversions (dimetalations) can be accomplished with spiny arenes (tert-butylbenzene, 1,4-di-tert-butylbenzene, 1,1,3,3-tetramethylindane and congeners) and N,N-crowded anilines (2,2,6,6-tetramethyl-1-phenylpiperidine and N,N-bis[triethylsilyl]aniline), albeit incompletely (av. and optimum yields of trapping products 25% and 41%, resp.). All the evidence points at an aggregate phenomenon. Dimetalation occurs only with an excess of a highly concd. butyllithium/K tert-butoxide mixt. in hydrocarbon media. In THF, no trace of a dimetalated species is found, although such species, once generated in a different manner, are moderately stable in this solvent at -75 Deg. 1,4-Dimetalloarenes are favored over the 1,3-isomers; 1,2-isomers do not form at all. As found by competition kinetics, 2,2,6,6-tetramethyl-1-phenylpiperidine and N,N-bis(triethylsilyl)aniline undergo monometalation at roughly the same rate as tert-butylbenzene and much more slowly than benzene does. [on SciFinder (R)]
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Baston, E., Maggi, R., Friedrich, K., & Schlosser, M. (2001). Dimetalation: the acidity of monometalated arenes towards superbasic reagents. European Journal of Organic Chemistry, (21), 3985–3989. https://doi.org/10.1002/1099-0690(200111)2001:21<3985::AID-EJOC3985>3.0.CO;2-Y
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2001
21
3985
3989
CAN 136:151221 29-6 Organometallic and Organometalloidal Compounds Section de Chimie (BCh), Universite,Lausanne,Switz. Journal 1434-193X written in English. 768-66-1 (2,2,6,6-Tetramethylpiperidine) Role: RCT (Reactant), RACT (Reactant or reagent) (condensation with bromobenzene); 108-86-1 (Bromobenzene) Role: RCT (Reactant), RACT (Reactant or reagent) (condensation with tetramethylpiperidine); 98-06-6 (tert-Butylbenzene); 1012-72-2 (1,4-Di-tert-butylbenzene); 4147-89-1; 4834-33-7; 91324-94-6; 113710-83-1; 393542-80-8 Role: RCT (Reactant), RACT (Reactant or reagent) (mono- and dimetalation reactions of); 393542-81-9P; 393542-82-0P; 393542-85-3P; 395082-53-8P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. and hydrolysis of); 94572-99-3P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. and metalation reaction of); 96927-48-9P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. and mono- and dimetalation reactions of); 14034-95-8P; 16308-65-9P (Dimethyl 5-tert-butylisophthalate); 26537-19-9P (Methyl 4-tert-butylbenzoate); 27330-57-0P (Methyl 3-tert-butylbenzoate); 31935-68-9P; 100971-92-4P; 127808-48-4P; 146271-67-2P; 180319-33-9P; 261788-75-4P; 261788-76-5P; 393542-83-1P; 393542-84-2P; 393542-86-4P; 393542-87-5P; 393542-88-6P; 393542-89-7P; 393542-90-0P; 395082-54-9P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. of)
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