Catalysis in aromatic nucleophilic substitution. Part 4. Reactions of piperidine with 2-methoxy-3-nitrothiophen in benzene

Abstract

The rate of piperidino-substitution of 2-methoxy-3-nitrothiophen (I) in benzene as a function of amine concentration has been studied. The reaction is strongly catalysed by piperidine, being third-order overall (second-order in amine) and represents the first example of an S_NAr of an ortho- or ortho-like mononitro-substituted derivative for which base catalysis is needed in benzene. The results obtained have been interpreted by taking into account the properties of the leaving group and its peculiar ortho-like relation with the activating nitro group.