Directed ortho metalation

Under an ortho- metalation (or English directed ortho metallation and abbreviated DoM ) is the metalation of appropriately substituted aromatics with alkyl lithium compounds. The substituents are as direct metalation group ( DMG or abbreviated ) referred and direct metallation, through their intermediate deprotonation at the ortho position of the aromatic. Examples of DMG are groups such as methyl, tertiary amine or amide group.

Mechanism

The aromatic with a DMG group interacts with the organolithium compound such as n- butyllithium, and breaks the aggregation cluster (R- Li ) n. This activates the organolithium compound in direct proximity to the ortho-hydrogen atom so that it is abstracted from the carbanion and thus the corresponding carbon atom is metalated. As it is in the DMG is a Lewis base, and lithium cations Lewis acids are the metallated aromatic compound is stabilized.

In a further step these metallated aromatic compound is then reacted with an electrophile and the product is obtained a normal nucleophilic substitution or addition.

This type of reaction have been published independently by Henry Gilman and Georg Wittig in 1939 and 1940, respectively.