In a model study, 3-fluorophenol and 3-fluoropyridine were converted into all possible regioisomers of the corresponding carboxylic acids by passing through the corresponding organometallic intermediates. As an attempt to generalize the findings reveals, a restricted set of principles and methods suffices to cope with all std. scenarios. The most valuable and versatile tools for the regiochem. exhaustive functionalization of a great variety of substrate patterns are the optionally site-selective metalation (either by reagent/substrate matching or by peripheral coordination control), the use of activating or congesting protective groups and the basicity gradient-driven heavy halogen migration (followed by halogen/metal permutation). [on SciFinder (R)]