Radical ion probes. Part 10. Ceric(IV) ammonium nitrate oxidation of cyclopropylarenes†

Abstract

The chemistry of radical cations generated via the oxidation of several cyclopropylarenes with ceric(IV) ammonium nitrate in CH₃CN–CH₃OH is reported. For cyclopropylbenzene, the major product is 1-phenylpropane-1,3-diyl dinitrate, arising from ring opening of the cyclopropylbenzene radical cation. Experiments with 1-cyclopropyl-4-methylbenzene reveal that ring opening of cyclopropylbenzenes occurs substantially faster than side chain deprotonation. Cyclopropane ring opened products are also formed in the oxidation of 1- and 2-cyclopropylnaphthalenes. For 9-cyclopropylanthracene however, ring opened products are not detected. Instead, all products arising from this reaction are attributable to reaction of nucleophiles with the aromatic ring. Overall, these results confirm and extend earlier observations pertaining to the chemistry of cyclopropylarene radical cations. General principles associated with the use of cyclopropyl groups as “probes” for radical cation intermediates, and general principles governing radical ion ring openings are discussed.