title: Regioselectivity in the nitration of dialkoxybenzenes.
abstract: Dinitrodialkoxybenzene derivatives are important precursors for Schiff base macrocycles and a variety of other molecules. During our investigations, we have found that the dinitration reaction of 1,2-dialkoxybenzenes proceeds with unusual regioselectivity, giving exclusively the desired 1,2-dialkoxy-4,5-dinitrobenzene product, but we have been unable to find a good explanation for this result. The dinitration of 1,4-dialkoxybenzene derivatives also exhibits surprising regioselectivity that has hitherto been left unexplained. Herein, we report a detailed DFT analysis of the regioselective dinitration of both 1,2- and 1,4-dimethoxybenzene. These results show that the reaction mechanism likely involves a single electron transfer (SET) process. In the case of the former isomer, the regioselectivity is mainly determined by the symmetry of the HOMO of the aromatic moiety that defines the structure of the SHOMO of the aromatic radical cation formed by the SET process. In the case of the latter isomer, the selectivity is due mainly to solvation effects and may thus be altered depending on the solvent environment. Synthetic studies of the nitration of 1,4-dialkoxybenzene derivatives using different solvent conditions support this conclusion and provide practical information for tuning the regioselectivity of the reaction.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada.
authors.forename: Kevin
authors.initials: K
authors.lastname: Shopsowitz
authors.forename: Francesco
authors.initials: F
authors.lastname: Lelj
authors.forename: Mark J
authors.initials: MJ
authors.lastname: MacLachlan
mesh_terms: D001555:Benzene Derivatives / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D001555:Benzene Derivatives