A variety of heteroatom-containing substituents promote lateral lithiation of an ortho methyl group. Generally, better results are obtained when the heteroatom is in the β position rather than the α position, as the latter tends to promote ortho lithiation. Lithation of primary benzylic positions is slower than lithiation of methyl groups due to inductive electron donation from the additional alkyl group (rather than steric effects). Electrophiles that react with the benzylic anions formed by these methods include aldehydes and ketones, activated (primary, allylic, or benzylic) halides, molecular oxygen, and silyl chlorides.  This section describes the scope of directing groups that may be used to effect site-selective lithiation in substituted benzenes and heterocycles.