Directed ortho Metalation (DOM)
The reaction of an alkyllithium compound with an arene bearing a "Directed Metalation Group" (DMG) normally leads to an ortho-metalated intermediate. Good DMG's are strong complexing or chelating groups that have the effect of increasing the kinetic acidity of protons in the ortho-position.
The ortho-metalated intermediate can be reacted with a variety of electrophiles, after which the DMG can be retained if desired, converted to a different functional group, or in some cases removed.
Mechanism of Directed Ortho Metalation
The DMG does not necessarily have to be inert:
|strong DMGs:||-CON-R, -CONR2,||-N-COR, -N-CO2R|
Directed Ortho-Metalation of Unprotected Benzoic Acids. Methodology and Regioselective Synthesis of Useful Contiguously 3- and 6-Substituted 2-Methoxybenzoic Acid Building Blocks
T.-H. Nguyen, A.-S. Castanet, J. Mortier, Org. Lett., 2006, 8, 765-768.
Selective Ortho and Benzylic Functionalization of Secondary and Tertiary p-Tolylsulfonamides. Ipso-Bromo Desilylation and Suzuki Cross Coupling Reactions
S. L. MacNeil, O. B. Familoni, V. Snieckus, J. Org. Chem, 2001, 66, 3662-3670.