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Paper | Special issue | Vol 37, No. 3, 1994, pp.1529-1540
Published online, 1st January, 1970
DOI: 10.3987/COM-93-S79
Substituent Effects in the Reactions of Some 2-Methoxy-3-nitro-5-X-thiophenes with Pyrrolidine and Piperidine in Methanol

Caterina Arnone, Giovanni Consiglio,* Vincenzo Frenna, Elisabetta Mezzina, and Domenico Spinelli

*Dipartimento di Chimica Organica 'A. Mangini', Via S. Donato 15, 40127 Bologna, Italy


The kinetics of the title reactions have been studied as a function of amine and methoxide ion concentrations in buffered solutions. All the reactions studied are general base-catalysed. An examination of the catalytic coefficients obtained for each mine-substrate system has showed that the catalysis observed occurs through a SB-GA mechanism and that the general base-catalysed productforming step is controlled by the ring size of the cyclic mine. The Hammett p1 values calculated are consistent with previous evidence concerning the interactions between the substituent at the C-5 para-like carbon atom and the leaving group. Moreover, the results confirm that a methyl group in such a position can behave as a weakly electron-attracting substituent.