Improved nitrations using metal nitrate-sulfuric acid systems

Procedures for efficient mono- and di-nitration of aromatic substrates have been developed using eerie ammonium nitrate suspended in dichloromethane i n the presence of 2 equiv. of sulfuric acid. By suspending the sulfuric aci d on silica gel following nitration, products are easily isolated by filtra tion and evaporation of solvent. In these nitrations eerie ammonium nitrate can be replaced by other metal nitrates, for example potassium- or tetrabu tylammonium-nitrate. In contrast the nitration of naphthalene by eerie ammo nium nitrate in the presence of methanol and sulfuric acid affords a mixtur e of 1,4- and 1,2-methoxynitronaphthalenes, but these nitrations cannot be achieved using potassium or tetrabutylammonium nitrate. The mechanism of th is nitration/oxidation is discussed. (C) 2000 Elsevier Science Ltd. All rig hts reserved.