Reactions of nitroanisoles. Part 2. Reactions of 2,4- and 2,6-dinitroanisole with piperidines in benzene

Abstract

The reactions of 2,4-(I) and 2,6-dinitroanisole (VIII) with piperidine (II) and N-methylpiperidine (NMP) in benzene have been studied. It was found that (I) and (VIII) react with (II) to give not only the expected aromatic nucleophilic substitution (a.n.s.) products, but also the corresponding dinitrophenols, generated by an S_N2 reaction. The rate for each reaction and the overall rates were measured and it was observed that compound (I) has similar rate coefficients for the a.n.s. as well as for the S_N2 reaction. Mild acceleration by base was found for the a.n.s. reaction. When (VIII) reacts with (II) the rate of reaction to form 2,6-dinitrophenol is greater than the rate for the a.n.s. In the reaction with NMP only an S_N2 reaction was observed. Furthermore, the rates of reaction of (VIII) with (II) and with NMP are ca. 1 000 and 300 times, respectively, the rate of reaction of (I) with these amines. A field effect is proposed for the increase in rate.