Regioselective control of electrophilic aromatic substitution reactions

para-Regioselective electrophilic aromatic substitution reactions, for example nitration, alkylation, acylation, sulfonylation and halogenation, can be achieved by carrying out reactions over solid catalysts such as zeolites, under modest conditions via shape-selectivity. By contrast, organolithium reagents can play an important role when ortho-products are desirable. ortho-Lithiation has been applied for the synthesis of more complex substituted heterocycles that are difficult to prepare by other means.