* In boronic ester homologization an alkyl group shifts from boron in a boronate to carbon:
In this reaction dichloromethyllithium converts the boronic ester into a boronate. A Lewis acid then induces a rearrangement of the alkyl group with displacement of the chlorine group. Finally an organometallic reagent such as a Grignard reagent displaces the second chlorine atom effectively leading to insertion of an RCH group into the C-B bond. Another reaction featuring a boronate alkyl migration is the Petasis reaction.