Meisenheimer-type adducts from thiophene derivatives. Part 6. A kinetic and thermodynamic study of substituent effects on the formation of some non-gem adducts

Abstract

The rate and equilibrium constants for the formation of the Meisenheimer-type adducts [(6) and (8)] from some 4-nitro-2-X-(5) or some 2-nitro-4-X-thiophenes (7) and sodium methoxide have been measured at 25 °C in methanol or methanol–dimethyl suiphoxide mixtures. The observed stability and reactivity patterns have been interpreted in the light of the hyper-ortho relation in the thiophene ring and the special ability of the nitro group to stabilize effectively the adducts from a para-like position also.