Hydroxy- and Alkoxy-substituted Toluenes

As mentioned above, the ammoxidation of toluenes substituted with electron-donating groups is rather less selective. The reaction can, nevertheless, be performed if optimum conditions (catalyst, feed composition, temperature) are carefully chosen. 

Ammoxidation of p-methoxytoluene (protection of the OH group in the p-cresol feed by methylation) over vanadium-titanium oxide catalysts gives p-methoxy-benzonitrile in 65 % yield [81,82]. Because of the greater reactivity of p-methoxy-toluene compared with the m isomer the ammoxidation of m,p-methoxytoluene mixtures results in the formation of only p-methoxybenzonitrile and the m isomer remains mainly unreacted. This presents the possibility of reactive separation of differently substituted toluenes [82]. 

Acylation as protection for the OH group seems not to be preferred because the acyl group is readily removed during reaction, resulting in a loss in selectivity. Thus, acetoxy-o-xylene can not be ammoxidized to acetoxyphthalic acid derivatives [84]. On the other hand, 9,10-bis(acetoxymethyl)anthracene has been converted to 10-(acetoxymethyl)-9-anthracenecarbonitrile in 64% yield [85]. 

The joint influence of the electron-donating effect, and the position, in polysub-stituted toluenes significantly hampers conversion and selectivity. This results in rather poor yields and selectivity, particularly for 2,6-disubstituted toluenes [e.g. 41,75]. 

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