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Journal article

Fluorine-flanked congested sites: Minimal, though perceptible buttressing effects on the proton mobility of arenes

(2,6-Difluorophenyl)trimethylsilane, -triethylsilane and -triisopropylsilane undergo sec-butyllithium-mediated metalation at the 3- and 4-position (ortho and meta relative to the halogen) in ratios of 99.6:0.4, 98:2 and 95:5, resp. The steric pressure transmitted by the fluorine atoms can be increased if the trialkylsilyl group is locked up on the other side by a relatively voluminous substituent. Whereas (2,6-difluorophenyl)triethylsilane is attacked by lithium 2,2,6,6-tetramethylpiperidide under deprotonation of the 4- and 5-position in a ratio of 99.4:0.6, the proportion of "ortho"/"meta" metalation changes to 84:16 when (2-bromo-6-fluorophenyl)triethylsilane acts as the substrate. [on SciFinder (R)]

    Keywords: Silanes Role: RCT (Reactant) ; SPN (Synthetic preparation) ; PREP (Preparation) ; RACT (Reactant or reagent) (aryl; fluorine-flanked congested sites ; minimal ; though perceptible buttressing effects on proton mobility of arenes); Steric effects (fluorine-fl ; fluorine proton mobility arene lithiation

    Note:

    CAN 144:87824 22-4 Physical Organic Chemistry Institute of Chemical Sciences and Engineering,Ecole Polytechnique Federale,Lausanne,Switz. Journal 1434-193X written in English. 1435-51-4 (1,3-Dibromo-5-fluorobenzene); 1435-52-5 (1,4-Dibromo-2-fluorobenzene) Role: RCT (Reactant), RACT (Reactant or reagent) (Grignard, carboxylation; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 768-35-4 ((3-Fluorophenyl)boronic acid); 1765-93-1 ((4-Fluorophenyl)boronic acid); 2265-93-2 (2,4-Difluoro-1-iodobenzene) Role: RCT (Reactant), RACT (Reactant or reagent) (Suzuki; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 865-47-4; 3030-47-5 (N,N,N',N'',N''-Pentamethyldiethylenetriamine) Role: RGT (Reagent), RACT (Reactant or reagent) (fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 5400-61-3P (2,3',4-Trifluorobiphenyl); 112704-79-7P (4-Bromo-2-fluorobenzoic acid); 161957-56-8P (3-Bromo-2-fluorobenzoic acid); 872545-53-4P (2,4,4'-Trifluorobiphenyl); 872545-54-5P (2,4-Difluoro-3-(trimethylsilyl)benzoic acid); 872545-55-6P (2,4-Difluoro-3-(triisopropylsilyl)benzoic acid); 872545-56-7P; 872545-57-8P (3,5-Difluoro-4-(triisopropylsilyl)benzoic acid) Role: SPN (Synthetic preparation), PREP (Preparation) (fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 109-72-8 (n-Butyllithium); 594-19-4 (tert-Butyllithium); 598-30-1 (sec-Butyllithium); 38227-87-1 (Lithium 2,2,6,6-tetramethylpiperidide) Role: RGT (Reagent), RACT (Reactant or reagent) (lithiating agent; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 872545-52-3P ((2-Bromo-6-fluorophenyl)triethylsilane) Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (lithiation, carboxylation, protodesililation; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 133117-48-3 ((2,6-Difluorophenyl)trimethylsilane); 651027-02-0 ((2,6-Difluorophenyl)triethylsilane) Role: RCT (Reactant), RACT (Reactant or reagent) (lithiation, carboxylation, thermal decompn.; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 872545-50-1P ((2,6-Difluorophenyl)triisopropylsilane) Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (lithiation, carboxylation, thermal decompn.; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 184910-20-1P ((4-Bromo-2,6-difluorophenyl)trimethylsilane); 872545-51-2P ((4-Bromo-2,6-difluorophenyl)triisopropylsilane) Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (lithiation, carboxylation; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 372-18-9 (1,3-Difluorobenzene); 461-96-1 (1-Bromo-3,5-difluorobenzene); 1073-06-9 (1-Bromo-3-fluorobenzene) Role: RCT (Reactant), RACT (Reactant or reagent) (lithiation, silylation; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes); 75-77-4 (Chlorotrimethylsilane); 994-30-9 (Chlorotriethylsilane); 13154-24-0 (Chlorotriisopropylsilane) Role: RCT (Reactant), RACT (Reactant or reagent) (silylating agent; fluorine-flanked congested sites, minimal, though perceptible buttressing effects on proton mobility of arenes)

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    Record created on 2006-03-03, modified on 2016-08-08

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