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

Heiss, ChristopheLeroux, FredericSchlosser, Manfred2006-03-032006-03-032006-03-03200510.1002/ejoc.200500552https://infoscience.epfl.ch/handle/20.500.14299/227027WOS:0002340301000158003(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)]Silanes Role: RCT (Reactant)SPN (Synthetic preparation)PREP (Preparation)RACT (Reactant or reagent) (aryl; fluorine-flanked congested sitesminimalthough perceptible buttressing effects on proton mobility of arenes); Steric effects (fluorine-flfluorine proton mobility arene lithiationFluorine-flanked congested sites: Minimal, though perceptible buttressing effects on the proton mobility of arenestext::journal::journal article::research article