- Proton mobility in 2-substituted 1,3-dichlorobenzenes: "ortho" or "meta" metalation?
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Nine 1,3-dichlorobenzene congeners were selected as model compounds to assess the relative rates of proton abstraction from 4- and 5-positions ("ortho" vs. "meta" metalation). Using lithium 2,2,6,6-tetramethylpiperidide as the basic reagent, the chlorine-adjacent 4-position underwent metalation exclusively. In contrast, attack at the chlorine-remote 5-posi" tion became significant even in the case of moderately sized 2-substituents (such as dimethylamino or ethyl) when secbutyllithium was employed. The "ortho/para" (4-/5-) ratios ranged from 80:20 to 65:35. The more pronounced "meta-orienting" effect of silicon as opposed to carbon substituents can be attributed to dissimilarities in the n polarization of the aromatic ring. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Schlosser, Manfred,Heiss, Christophe,Marzi, Elena,Scopelliti, Rosario
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p. 4398 - 4404
(2007/10/03)
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- Metalation and derivatization of all six dichlorobenzotrifluorides: Site selectivities
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The metalation of 2,3-, 2,6-, 2,4- and 3,5-dichlorobenzotrifluorides can be readily effected with standard reagents such as lithium diisopropylamide, lithium 2,2,6,6-tetramethylpiperidide, and butyllithium at the chlorine-adjacent 4- and 3-positions and t
- Masson, Eric,Marzi, Elena,Cottet, Fabrice,Bobbio, Carla,Schlosser, Manfred
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p. 4393 - 4400
(2007/10/03)
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