Ozone-mediated reaction of anilides and phenyl esters with nitrogen dioxide: enhanced ortho-reactivity and mechanistic implications

Abstract

In the presence of ozone, anilides 1 can be nitrated rapidly with nitrogen dioxide in chloroform at 0 °C to give a high proportion of ortho-nitro derivatives (ortho : para= 1.2–4.4) in good yields. The phenyl esters 15 can be similarly nitrated on the aromatic ring without significant cleavage of the ester bond, giving a mixture of isomeric nitro derivatives in which the ortho-isomer predominates (ortho : para= 1.1–1.5). The origin of the enhanced ortho reactivity is discussed in terms of an electron-transfer process involving the nitrogen trioxide as initial electrophile.