Catalysis in aromatic nucleophilic substitution. Part 7. Kinetics of the reactions of some 5-substituted 2-methoxy-3-nitrothiophenes with piperidine in benzene

Abstract

The kinetics of the reactions of some 2-methoxy-3-nitro-5-X-thiophenes (Ia–g; X = H, CONH₂, CO₂Me, Ac, SO₂Me, CN, or NO₂) with piperidine and with n-butylamine in benzene have been measured in the range 20–40 °C. The reactions with piperidine are catalysed by piperidine, being third-order overall (second-order in amine). The electronic effects of the 5-substituent on the ‘catalytic’ constants are shown to be most consistent with the SB-GA mechanism of base catalysis in benzene.