Experiments on the chaperon effect in the nitration of aromatics

A nitro group may be effectively delivered to the ortho position of alkylbenzenes, provided that a suitable chaperon function is located in alpha-position and a dilute solution of HNO3 in CH2Cl2 is used. The carbonyl function of an aldehyde or ketone is the best choice, but a carboxyl, alkoxycarbonyl, and amide groups all work well. The ether function showed a less pronounced or tho orientation effect, whereas the hydroxyl group was too prone to oxidation. Side reactions were minimal under the conditions employed. A para chaperon effect was seemingly at work in the CH2Cl2 nitration of benzenepropanenitrile. All the results mere compared with the corresponding classical nitration in H2SO4.