ipso Nitration in p-halophenyl ethers

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Abstract
Addition of nitronium ion ipso to halogen occurs on nitration of the p-haloanisoles in acetic anhydride at −60 °C. In the cases of p-fluoro- and p-chloro-anisole, addition of the nitronium ion is reversible and only small amounts of ipso products are obtained. With p-bromoanisole nitrodebromination occurs. When p-halophenyl ethers containing a trapping substituent, e.g., 2-(4-chlorophenoxy)-2-methylpropanoic acid, are used as substrates, substantial amounts of the spiro diene with nitro ipso to halogen, e.g., 3,3-dimethyl-8-chloro-8-nitro-1,4-dioxaspiro[4.5]deca-6,9-dien-2-one, can be isolated. The results demonstrate that extensive ipso attack at the halogen-substituted position is general in the nitration of p-halophenyl ethers. Keywords: ipso nitration, ether, diene, p-haloanisole.

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