Ipso Nitration. Preparation of 4-Methyl-4-nitrocyclohexadienols and Detection of Intramolecular Hydrogen Migration (NIH Shift) upon Solvolytic Rearomatization

4-Alkyl-4-nitrocyclohexadienols are formally the 1,4 adducts of nitric acid and the parent alkylbenzene. Evidence of formation of these ipso nitration products during nitration in aqueous systems is convincing, although none of these intermediates have been isolated from direct nitration. In contrast, the acetate derivatives of these nitrodienols have been repeatedly isolated from nitrations in acetic anhydride. We have found that several 4-methyl-4-nitrocyclohexadienols may be readily prepared by reduction of the corresponding 4-methyl-4-nitrocyclohexadienones, and we report here studies of the solvolytic behavior that illustrate some interesting differences in the reactivity of nitrodienols and their acetate derivatives.