Review on the metallation of π -deficient heteroaromatic compounds

These results allow to select the best 3-fluoropyridine-metallation conditions which lead to 3-fluoro-2-lithiopyridine on the one hand and to 3-fluoro-4-lithiopyridine on the other hand. Each of the lithiated isomers is then reacted with a great variety of electrophiles which gives very conveniently the corresponding 2,3- or 3,4-disubstituted pyridines.