The effect of an alkoxy group on the kinetic and thermodynamic acidity of benzene and toluene

2-, 3- and 4-Methoxytoluene can be selectively metalated at an O-adjacent ortho position when butyllithium or tert-butyllithium in the presence of sodium (potassium) tert-butoxide or N,N,N′,N″,N″-pentamethyldiethylenetriamine are employed as reagents. In contrast, lithium diisopropylamide or lithium...

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Bibliographic Details
Published inTetrahedron Vol. 54; no. 12; pp. 2763 - 2770
Main Authors Schlosser, Manfred, Maccaroni, Paola, Marzi, Elena
Format Journal Article
LanguageEnglish
Published Elsevier Ltd 19.03.1998
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Summary:2-, 3- and 4-Methoxytoluene can be selectively metalated at an O-adjacent ortho position when butyllithium or tert-butyllithium in the presence of sodium (potassium) tert-butoxide or N,N,N′,N″,N″-pentamethyldiethylenetriamine are employed as reagents. In contrast, lithium diisopropylamide or lithium 2,2,6,6-tetramethylpiperidide deprotonate the benzylic α-position of 2- and 3-methoxy-toluene exclusively and of 4-methoxytoluene preferentially. These relative reactivities can be rationalized by an interplay of transition state stabilizing and destabilizing forces (dipole matching and metal coordination vs. lone pair repulsion). Graphic
ISSN:0040-4020
1464-5416
DOI:10.1016/S0040-4020(98)83011-1