title: Atom-efficient electrophilic aromatic nitration by dinitrogen pentoxide catalysed by zirconium(IV) 2,4-pentanedionate.
abstract: An atom-efficient, non-acidic, catalytic process is described for the nitration of electron deficient arenes such as o-nitrotoluene using a dinitrogen pentoxide-zirconium(iv) 2,4-pentanedionate system in dichloromethane solvent. Kinetic studies showed the nitration process to be first-order with respect to the aromatic substrate and higher than first-order with respect to the catalyst. Addition of the catalyst at ca. 0.1-1 mol% compared with both N(2)O(5) and the organic substrate results in an increase in the first-order rate constant for nitration by a factor of approximately 5000 with a turnover number of at least 500. The orientation of the nitration products (2,4-/2,6-dinitrotoluenes) is consistent with attack of nitronium ion. The apparently high order of reaction with respect to the catalyst suggests a possible heterogeneous process.
authors.affiliation: Department of Chemistry, University of Exeter, Stocker Road, Exeter, UKEX4 4QD.
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Hill
authors.forename: Ross W
authors.initials: RW
authors.lastname: Millar
authors.forename: John P B
authors.initials: JP
authors.lastname: Sandall