Catalysis in aromatic nucleophilic substitution. Part 5. Reactions of piperidine with methyl 2-methoxy-3-nitrothiophen-5-carboxylate and 5-acetyl-2-methoxy-3-nitrothiophen

Abstract

The kinetics of piperidino-substitution of methyl 2-methoxy-3-nitrothiophen-5-carboxylate (lb) and of 5-acetyl-2-methoxy-3-nitrothiophen (lc) have been studied in methanol as a function of piperidine and methoxide ion concentrations. The reactions are catalysed by both piperidine and methoxide. Evidence is presented that the departure of the methoxy group is general-acid-catalysed, indicating a specific base-general acid mechanism for base catalysis.