Clay catalysed nitrodecarboxylation of aromatic acids

Nitration ofp-anisic acid in clay microenvironment yields 2,4-dinitroanisole in about 40–60% yield, in addition to the conventional nitration product, namely 3-nitro-4-methoxybenzoic acid. While clay directed nitration ofp-methoxyacetophenone gives only 3-nitro-4-methoxy-acetophenone, withm-nitrobenzoic acid, nitrodecarboxylation yieldingm-dinitrobenzene is the only reaction course. The observed greater ipso-nitration facilitated by a nitro group may be attributed to the greater ease with which the Wheland intermediate may decompose via a cyclic six-membered transition state.